OPC UA

Introduction

OPC Unified Architecture (OPC UA) is a standard pushed by the OPC Foundation for industry automation. The goal of OPC UA is to enable the communication between industrial devices. OPC UA is designed to work across technology boundaries (cross-platform). There are two components designed to accomplish this integration:

• OPC UA device gateway
• OPC UA management service

The OPC UA device gateway is a stand-alone Java program that communicates with OPC UA server(s) and the Cumulocity platform. It stores data into the Cumulocity database via REST. Additionally, C8Y commands are executed to perform various operations on the OPC UA servers.

The gateway must be registered as Cumulocity device in a specific tenant and the opcua-device-gateway must run in the users’ environment.

To download the gateway navigate to Cumulocity resources.

The gateway requires Java 11 in order to run.

Gateway configuration and registration

YAML file and spring profiles are used for the configuration of the gateway. A default configuration file is embedded in the gateway JAR file, so you only must set the properties which are different from the default.

To run the gateway locally, the default settings should be overridden in a customized profile. To use the customized profile, create a YAML file which must follow the naming convention:

application-<<Profile_name>>.yaml

For example, to connect to a tenant, first a profile named application-myTenant.yaml will be created. The following properties will be added to the file:

C8Y:
    baseUrl: https://<<yourTenant>>.cumulocity.com
gateway:
    bootstrap:
        tenantId: <<yourTenantId>>
    identifier: Gateway_Device
    name: Gateway_Device
    db:
# The gateway uses the local database to store platform credentials and local cache. This parameter shows the location in which the local data should be stored.
        baseDir: C:/Users/<<userName>>/.opcua/data

Thin Edge

The OPC UA gateway can also be registered and operated via thin-edge.io. In contrast to the standalone mode, thinEdge configurations must be added to the YAML file:

C8Y:
    baseUrl: https://<<yourTenant>>.cumulocity.com
gateway:
    bootstrap:
        tenantId: <<yourTenantId>>
    identifier: Gateway_Device
    name: Gateway_Device
    db:
# The gateway uses the local database to store platform credentials and local cache. This parameter shows the location in which the local data should be stored.
        baseDir: C:/Users/<<userName>>/.opcua/data
    thinEdge:
        enabled: true
        mqttServerURL: tcp://<<thinEdge MQTT broker>>
        deviceId: Thin-Edge_Device

With the configuration gateway.thinEdge.enabled: true you switch to the thinEdge mode. This means that the authentication and registration to the platform will be done via Thin Edge. The OPC UA gateway is automatically registered and created as a sub-device under the Thin Edge device. gateway.thinEdge.mqttServerURL and gateway.thinEdge.deviceId are the connection information for the MQTT client to connect to the local Thin Edge MQTT broker.

Configuration profile location on the filesystem

The configuration profile can be stored either in the same directory as the JAR file or in a default configuration directory. Depending on the operating system, the following default configuration directories can be used:

Windows OS
    /C:/opcua/
Linux OS
    /etc/opcua/
    /etc/opcua/data
Mac OS
    /opt/opcua/
    /opt/opcua/data

The number of profiles you may have is not limited. To use a specific profile on runtime, the “–spring.profiles.active” JVM argument must be passed when running the gateway JAR file. For example, let’s use the previously created profile. Start a terminal and use the following command:

java -jar opcua-device-gateway-<<version>>.jar --spring.profiles.active=default,myTenant

The command above will start a gateway with the default profile and it will override the default properties with the properties defined in the “myTenant” profile. The list of profiles must be provided as an ordered, comma-separated list. The default profile must always be the first profile in the list.

Optional: To specify your own configuration, Spring arguments can be used in your terminal to run the gateway JAR file. Multiple locations must be comma-separated. The configuration locations should be either YAML files or directories. In case of directories, they must end with “/”. For example:

java -jar opcua-device-gateway-<<version>>.jar --spring.config.location=file:<<location>>/.opcua/conf/application-myTenant.yaml,file:<<location>>/.opcua/conf/

If both arguments “–spring.config.location” and “–spring.profiles.active” are provided, the configuration locations should be directories instead of files. Otherwise, the profile-specific variants will not be considered.

Additional customizations

The following properties can be manually configured in the YAML file:

# Name of the application - this should not change
name: opcua-device-gateway
# Platform location and configuration
C8Y:
  # This is the base URL pointing to the Cumulocity platform. This must always be customized in an application profile.
  baseUrl: http://localhost
  # This is an internal setting of the Cumulocity SDK. It is set to true, because we typically
  # want to configure the Cumulocity SDK to always use the baseURL provided during initialization.
  # Otherwise, the gateway would use the links in the `self` fragment of the core API responses as the host name.
  # This is helpful in deployment scenarios where the Cumulocity instance is
  # reachable only with an IP address.
  forceInitialHost: true

#
# Gateway-specific settings
#
gateway:
  # The version of the gateway - this is filled automatically during the build process - do not change this property
  version: ${project.version}
  # The following two properties will be set to the name of the user that is running the gateway unless it's overridden manually
  identifier: mygateway
  name: mygateway
  # The gateway uses a local database to store platform credentials and a local cache. This setting tells
  # where local data is stored.
  db:
    baseDir: ${user.home}/.opcua/data
    addressSpace:
      # Starting from version 10.11, the opcua-device-gateway process creates the address space local db files are with a new filename
      # (cumulocity-opcua-server-<serverId>-address-space-pv4.bin) due to a dependency change to avoid conflicts.
      # The legacy address space local db files can be cleaned up at the start of the opcua-device-gateway process
      # automatically when the legacyCleanup is set to true, which is the default setting.
      # If the legacy files wanted to be kept or if the mechanism for clearing is not needed, set legacyCleanup to false.
      legacyCleanup: true
  # These settings configure and enable/disable Thin Edge mode (registration and operating OPC UA gateway via Thin Edge).
  thinEdge:
    # Enable Thin Edge if the OPC UA gateway is running next to Thin Edge and should use it to connect to Cumulocity.
    # Set enabled to false if the OPC UA gateway is running without Thin Edge.
    enabled: false
    # MQTT Server URL of Thin Edge (localhost).
    mqttServerURL: tcp://127.0.0.1:1883
    # Enable this if the MQTT client uses a single steady connection. Note that MQTT is only used to retrieve the JWT, which is dependent on how long the JWT is valid. See https://cumulocity.com/guides/device-integration/mqtt/#jwt-token-retrieval.
    # We recommend you to use a steady connection only if the JWT is valid for a short time. If the JWT is valid for a longer time, the standard is one hour. It is generally not recommended to have a steady MQTT connection.
    mqttSteadyConnection: false
    # The Thin Edge deviceId must be changed, depending on the configured deviceId of the Thin Edge certificate.
    deviceId: my-thin-edge-device
  # These settings control the device bootstrap process of the gateway.
  # In general, the default settings are sufficient, and should not be changed.
  # Contact product support (https://cumulocity.com/guides/<latest-release>/additional-resources/contacting-support/).
  # in case the bootstrap credentials are different.
  bootstrap:
    # Tenant ID to be used for device bootstrap
    tenantId: management
    # Credentials for the device bootstrap user
    username: devicebootstrap
    password: <devicebootstrap user password>
    # When the gateway starts, it waits <delay> milliseconds before connecting to the platform and searching for
    # the device.
    delay: 5000
    # If set to true, the gateway will drop any stored device credentials and fetch new ones from the platform.
    force: false

  # Scheduled tasks and thread pools configuration
  # Only change the settings here if really necessary. Wrong scheduler configurations can
  # disturb the gateway's operation.
  scheduler:
    # Threadpool specific settings
    threadpool:
      # This setting corresponds to the size of the threadpool used for periodic tasks.
      size: 15
  # These settings control the threadpool of our internal task executor, which is used for generic background
  # execution and asynchronous tasks.
  executor:
    threadpool:
      coreSize: 30
      maxSize: 60
  # The following settings control the settings of the device type mappings execution.
  mappingExecution:
    # This section contains all settings related to external, custom-action execution.
    http:
      # Connection request timeout (milliseconds)
      connectionRequestTimeout: 3000
      # Connection timeout (milliseconds)
      connectionTimeout: 3000
      # Socket timeout (milliseconds)
      socketTimeout: 5000
      # Maximum number of connections via HTTP route
      maxPerRoute: 100
      # Maximum total size of the HTTP connection pool used for external, custom actions.
      maxTotal: 100
      # The inactivityLeaseTimeout setting defines a period, after which persistent connections to
      # the HTTP server must be reevaluated. See PoolingHttpClientConnectionManager for more information
      inactivityLeaseTimeout: 50000 #ms
      # Aggregate number of alarms if something goes wrong with the execution of external custom actions
      failureAlarmAggregate: true
      # How often is the alarm aggregation for failed external calls invoked?
      failureAlarmFixedDelay: 15 # seconds
      failureHandling:
        # Whether a failed HTTP POST should be retried later or not. This can be overridden by the configuration in device type. Default is false
        enabled: false
        # Number of retries a failed HTTP POST will be resent
        maxRetries: 5
        # If retry is enabled, the exceptions of HTTP status codes can be provided here, comma separated. A HTTP POST which failed with one of these codes will not be retried. This can be overridden by the configuration in the device type. Default is empty which means that all failed http posts will be retried if enabled. Example: 400,500
        noRetryHttpCodes:
        # Minimum delay in seconds between two retries
        retryDelay: 120
      # Max queue size of the HTTP POST actions queue
      maxQueueSize: 50000
      # Worker thread (which performs the actual HTTP request) pool size
      threadPoolSize: 200

    # Threadpool configuration for the mapping execution
    # Each value arriving in the gateway will be handled by one or more action handlers defined in the device type. Each handler will be executed in one single thread.
    # Hence, this threadpool must be large enough to cope with the parallel processing needs of values
    # received from the OPC UA server.
    threadpool:
      size: 200

    # To avoid many REST calls to the inventory an in-memory map with a crash backup functionality is included.
    alarmStatusStore:
      # Expected number of maximum alarms at the same time
      maxEntries: 100000
      # The average size of the keys on the map. Needed for calculation of the size of the database file.
      averageKeySize: 30
      # The number of maxEntries multiplied with this factor results in the real max size of the database file. Resize is done only if needed.
      maxBloatFactor: 5.0

  # Mapping-specific settings
  mappings:

  # In OPC UA, alarm severity is specified by an integer range between 0 and 1000. The alarmSeverityMap
  # allows to configure how OPC UA severity is mapped into Cumulocity severity levels. The following is the default mappings:
  # alarmSeverityMap:
    # 1001: CRITICAL
    # 801: CRITICAL
    # 601: MAJOR
    # 401: MINOR
    # 1: WARNING

    # Mapping synchronization interval
    # The OPC UA gateway periodically fetches the OPC UA device types. With the following settings, this
    # interval can be adjusted.

    # Sync interval in milliseconds. The default is 43200000ms (12 hours)
    syncInterval: 43200000

  # Operation settings
  operation:
    # Default behavior that controls if the OPC UA gateway performs an address space scan when it connects the first time to an OPC UA server. Can be overridden in the OPC UA Server config.
    autoScanAddressSpace: true
    # Validates if the nodes given for the operation belongs to device's address space. If the validation fails an alarm is created for the device. If disabled, the opcua-device-gateway will execute the operation directly. The default is set to true.
    validateDeviceOperationNodes: true
  # Cyclic-Reader settings
  cyclicRead:
    # The cyclic readers use a dedicated threadpool to perform periodic read tasks.
    threadpool:
      # Allows the size of the threadpool for cyclic reads to be configured
      size: 30
    # How many nodes can be read at once for the cyclic read of the same device protocol, server, root node and the same parameters (rate, max-age).
    defaultBulkSize: 1000

  # OPC UA subscription settings: These settings allow global OPC UA configuration parameters
  # for subscription-based data reporting
  subscription:
    # The reporting rate (in milliseconds) corresponds to the publishing rate for monitored items.
    reportingRate: 100
    # The maxKeepAliveCount specifies the maximum number of OPC UA reporting intervals with no data that
    # can be skipped before the OPC UA server sends an empty response to the gateway, informing about
    # a yet active, but idle OPC UA subscription.
    maxKeepAliveCount: 200
    # The lifeTimeCount specifies the maximum number of reporting intervals without a value being sent.
    # After the lifetime count has exceeded, the subscription is terminated.
    # Must be 3 times greater than maxKeepAliveCount
    lifetimeCount: 600
    # The notificationBufferSize defines how many monitored item values should be buffered to receive
    # subscription notification data from the OPC UA server. The subscription reporting rate (publish interval)  
    # and the volume of sampling data should be taken into account to choose a suitable buffer size.
    notificationBufferSize: 500
    # The recreateFailedItems flag can be used to enable the feature of a subscription so that it automatically retries to create the monitored items
    # if they fail due to error code Bad_NodeIdUnknown. It assumes that the NodeIds are correct, but it hasn't been added to the
    # server's address space yet. The default value is false.
    recreateFailedItems: false

  # Subscription update settings
  subscriptionUpdate:
    # The subscription update interval controls how often the OPC UA gateway updates the subscription
    # settings for connected OPC UA servers. Expects: Interval duration in milliseconds.
    interval: 60000

  # Server connectivity configuration
  connectivity:
    # If autoReconnect in the client configuration is set to false, the gateway tries to reconnect manually.
    # triggerManualReconnectOnConnectionDrop can be used to stop the manual reconnect as well if set to false. The default value is true.
    triggerManualReconnectOnConnectionDrop: true

    # As a default, the OPC UA stack validates the endpoints returned by the OPC UA server. With this
    # setting, the default can be toggled.
    # This global setting can be individually overridden for each OPC UA server using the
    # "validateDiscoveredEndpoints" configuration fragment.
    # validateDiscoveredEndpoints: true

  # Internal repository configurations
  repositories:
    # Interval in milliseconds describing how often the repositories are flushed to the platform
    flushInterval: 10000
    # Threadpool size for the event queue flushing
    eventsThreadpool: 30
    # Threadpool size for the alarm queue flushing
    alarmsThreadpool: 30
    # Threadpool for the measurement queue flushing
    measurementsThreadpool: 60

    # Maximum capacity. If a repository grows over this size, the OPC UA communication will be shut off!
    maximumCapacity: 250000

    # Re-enable threshold. If OPC UA communication has been disabled due to exceeding maximum capacity, this threshold
    # controls when OPC UA communication is enabled again
    reenableThresholdSize:  10

  # The settings below describe platform-specific connection parameters.
  platform:
    inventory:
      update:
        # Default processing mode for inventory managed objects update to the Cumulocity platform.
        defaultProcessingMode: QUIESCENT
        # Processing mode for inventory update of the gateway device managed objects to the Cumulocity platform.
        gateway:
          processingMode: QUIESCENT
        # Processing mode for inventory update of the OPC UA server device managed objects to the Cumulocity platform.
        server:
          processingMode: QUIESCENT
        # Processing mode for inventory update of value-map managed objects to the Cumulocity platform.
        valuemap:
          processingMode: QUIESCENT
    # Connection pool configuration
    connectionPool:
      # Overall maximum size of the connection pool
      max: 250
      # Max connections used for a single host
      perHost: 150

  # Gateway self-monitoring configuration

  # First, the gateway internally measures different metrics and populates them to the platform.
  # Second, the gateway actively checks if a server connection is active and working by regularly
  # browsing the root node of an OPC UA server.
  monitoring:
    # The interval below in milliseconds configures the frequency of this monitoring task.
    interval: 10000
    # The interval below in milliseconds configures how often we investigate the thread executor queue sizes to prevent overflow
    checkQueueSizes: 10000

  # The OPC UA gateway persists all latest values of an OPC UA server in a dedicated managed object,
  # the so-called value map. These value maps are locally kept on the device for a certain time
  # before being pushed to the platform, allowing for local aggregation of all last-seen values.
  valueMap:
    # The lifetime of a local value map in seconds
    lifeTime: 30

  # How often (in milliseconds) does the gateway check for changes in configured servers.
  # This setting controls how long it takes for the gateway to discover an added or a removed server
  childrenAddedOrRemoveCheck:
    interval: 15000

  # How often (in milliseconds and if enabled) the gateway reads pending operations from the platform.
  shortPolling:
    enabled: true
    fixedDelay: 15000

  # Time in days for which the certificate is valid.
  applicationIdentity:
    validityTime: 3650

  # Timeout scanning address space in minutes and a pause between retries in milliseconds
  scanAddressSpace:
    timeout: 1440
    retries: 5
    pauseMillisForRetry: 700

Logging

Custom logging configuration can be set during startup by passing the “–logging.config” JVM argument. For more info on how to set up custom logging settings, refer to the “Logback” documentation. A sample logging configuration file may look like this:

<?xml version="1.0" encoding="UTF-8"?>
<configuration scan="true" scanPeriod="30 seconds">

       <include resource="org/springframework/boot/logging/logback/defaults.xml" />
       <appender name="FILE"
                         class="ch.qos.logback.core.rolling.RollingFileAppender">
               <file>/${user.home}/.opcua/log/device-gateway.log</file>
               <encoder>
                       <pattern>${FILE_LOG_PATTERN}</pattern>
               </encoder>

               <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
                       <!-- rollover daily -->
                       <fileNamePattern>/${user.home}/.opcua/log/device-agent-%d{yyyy-MM-dd}.%i.log
                       </fileNamePattern>
                       <timeBasedFileNamingAndTriggeringPolicy
                                       class="ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP">
                               <maxFileSize>50MB</maxFileSize>
                       </timeBasedFileNamingAndTriggeringPolicy>
                       <maxHistory>5</maxHistory>
               </rollingPolicy>
       </appender>

       <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
               <encoder>
                       <pattern>${CONSOLE_LOG_PATTERN}</pattern>
                       <charset>utf8</charset>
               </encoder>
       </appender>

       <logger name="com.cumulocity.opcua.client.gateway" level="INFO" />
       <logger name="com.cumulocity" level="INFO" />
       <logger name="c8y" level="INFO" />

       <root level="INFO">
               <appender-ref ref="FILE" />
               <appender-ref ref="STDOUT" />
       </root>
</configuration>

Deletion of gateway

An OPC UA gateway can be associated with multiple OPC UA servers, and the servers can have multiple child devices connected to them. The cleanest approach to delete a gateway is to first delete the OPC UA server managed objects and all its child devices.

The server can be either deleted from the OPC UA server tab of the gateway (recommended way of deletion), or from the device list itself. If the server is deleted from the OPC UA server tab, then the server managed object and all the address space managed objects are deleted by the OPC UA management service, but the child devices associated with the server must be deleted separately.

On the other hand, if the server is deleted from the device list, then the child devices associated with the server can be deleted by selecting the checkbox Also delete child devices of this device. The deletion is detected by the gateway, and the address space managed objects are deleted for the corresponding server. If the gateway is offline, then the address space managed objects will not be removed.

The process of deletion is asynchronous for both cases, so it may take a while to completely remove all the associated managed objects. Thereafter, the gateway can be deleted from the list of devices along with the device user by selecting the checkbox Also delete associated device owner “device_<gateway_name>”.

If the gateway is directly deleted from the list of devices before deleting gateway’s servers and devices of those servers, by selecting the checkbox Also delete child devices of this device, then the server managed object will be deleted, but the corresponding address space objects will not be deleted as they are not children of the gateway.

Downgrade to an earlier version

Due to security improvements, downgrades from 10.12.0 to previous versions are not directly supported. However, if required, a downgrade is possible by following the instructions below:

1. Shut down the current version of the gateway and remember the gateway managed object ID from the devices list.
2. Send an HTTP PUT command to your tenant to reset the identity:

PUT {url_to_your_tenant}/inventory/managedObjects/{device_id}

   {
   "c8y_ua_IdentityConfig":null
   }

3. The response code should be 200 OK.
4. Start the old version of the gateway.

After completing these steps a new identity will be created in the old structure.

It is possible to upgrade to version 10.12.0 or above at a later stage. The necessary conversion will be done automatically.

Running the Gateway

The gateway can run with either default or custom settings. To run the gateway run one of the commands below:

• Default settings and default logging configuration:

    java -jar opcua-device-gateway-<<version>>.jar
  

• Custom settings and default logging configuration:

    java -jar opcua-device-gateway-<<version>>.jar --spring.profiles.active=default,PROFILE_NAME
  

• Custom settings and custom logging configuration:

    java -jar opcua-device-gateway-<<version>>.jar --spring.profiles.active=default,PROFILE_NAME --logging.config=file:PATH_TO_LOGBACK_XML
  

For example, using the profile from the previous section we are going to register the gateway. First, open the terminal and navigate to the location of the gateway.jar file. Next, enter the following command:

java -jar opcua-device-gateway-<<version>>.jar --spring.profiles.active=default,myTenant

Adjusting gateway memory settings

In certain scenarios it is required to adjust the memory settings of the gateway application. Examples for such scenarios are the integration of servers with very large address spaces or obtaining large amounts of data from servers using high sampling rates.

You can adjust the memory settings of the gateway like with any other Java program. Typically, it is sufficient to increase the initial heap size and the maximum heap size of the gateway process.

• Example: Run the gateway with a minimum heap size of 2 GB and a maximum heap size of 8 GB.

  java -Xms2g -Xmx8g -jar opcua-device-gateway-<<version>>.jar
  

Performance tuning for large setups

If you’re running your setup with a large number of connected OPC UA servers the scan of these nodes can take a long time and may fail with the default settings. There are a lot of other problems like data collection and synchronisation, subscriptions, cyclic reads and flushing data. We recommend you to tune the following settings in the configuration YAML file (values are just examples of a known large setup):

gateway:  

  scheduler:
    threadpool:
      size: 300  

  executor:
    threadpool:  
      coreSize: 600  
      maxSize: 1200

If cyclic read (only subscription) is used we recommend

  cyclicRead:
    threadpool:
      size: 3000

otherwise size 0 is perfect.

In general, a larger number of threads will increase your performance. To increase the number of threads, add more memory.

Registering the gateway as a Cumulocity device

1. Click Registration in the Devices menu of the navigator.

2. Click Register device at the right of the top bar and from the dropdown menu select Single registration > General.

3. Enter the Device ID (in our example it is “Gateway_Device”) and then click Next.

4. Click Accept to complete the registration.

Gateway device details

After the registration is completed, the gateway device will be created by the opcua-device-gateway.

In this section, only OPC UA specific information related to the tabs in the device details page will be explained. For more info on all tabs, see Viewing device details.

Connecting the gateway to the server

Next, establish a connection between the gateway and the OPC UA server.

1. In the OPC UA server tab of the respective gateway, click Add server.
   
2. Use the Server connection toggle, to enable or disable the server connection.
3. Enter the Server URL which is used to establish a connection between the server and the gateway.
4. Enter the Timeout value in seconds. The timeout value is calculated for each request. If the timeout value is exceeded the request will be unsuccessful.
5. Enter the Status check interval in seconds. The status check interval specifies how often the gateway actively checks if the server status has changed. These periodic checks are carried out by reading the ServerStatus variable on the OPC UA server.
6. Select the Security mode and Security policy depending on the server configuration. For more info, see Security modes.
7. Select the desired authentication method. For more info, see Authentication.
8. Click Save.

Security modes

The security mode settings tell the gateway how it should secure the connection between itself and the OPC UA server. When a mode other than NONE is selected, the gateway will auto-generate a self-signed application instance certificate and will use it to connect to the server. Possible security mode options are:

• NONE
• BASIC128RSA15_SIGN
• BASIC128RSA15_SIGN_ENCRYPT
• BASIC256_SIGN
• BASIC256_SIGN_ENCRYPT
• BASIC256SHA256_SIGN
• BASIC256SHA256_SIGN_ENCRYPT

Authentication

The authentication setting is used to authenticate and authorize the server user. It tells the gateway how to create a user identity and how to send it to the OPC UA server when establishing a connection.

The following authentication methods can be selected:

• Anonymous - Will only work when the OPC UA server allows such connections.
• Username/Password - With this setting the gateway will connect to the server as a specific user represented by a username and password.
• Key-based authentication - The gateway will use an existing certificate to authenticate as a specific user. JKS keystore must be uploaded to Cumulocity as a binary with type “application/octet-stream”. This keystore must follow the following rules:
  • It must be a Java keystore (JKS).
  • The keystore itself must be password-protected.
  • The keystore must contain a user certificate with the “opcuauser” alias.
  • The user certificate must be password-protected.

The keystore can be created via the following Java keytool command:

keytool -genkey -keyalg RSA -alias opcuauser -keystore keystore.jks -storepass passw0rd_a -validity 3600 -keysize 2048

With the above command, the key pass is set to the same value as the keystore password.

The keystore can be verified by using a tool like KeystoreExplorer. It can then be uploaded to Cumulocity as a binary and used in the server configuration.

Child devices

All server connections are listed as child devices even if the servers are disconnected. To stop a server connection, either delete the server child device or disable/remove the connection from the OPC UA server tab.

Address space

When you navigate to the child device of the gateway, the Address space tab shows the attributes and references of the address space node of the servers. The filter searches through the whole hierarchy to find “nodeId”, “browserName” or “displayName” of an attribute. In case of multiple “ancestorNodeIds”, you can click on the desired node to be redirected.

The address space is automatically scanned when a connection between the gateway and the server is established. The duration of the scan depends on the size of the address space. The address space information is stored locally once it is scanned and then used by this applying process. If the address space information is not yet available, for example, the address space has not been scanned, another scan will be triggered without synchronizing data into Cumulocity. Performing another address space operation will update the address space information.

In case a node cannot be read, the scan process skips this node and continues. An error entry is written to the opcua-device-gateway log file to provide information (more information available in debug level).

Monitoring measurements

On the gateway device, the Measurements tab provides visualization of data in the form of charts. In total the gateway contains the following six charts:

Monitoring measurement details

The following is the full list of monitoring measurements created by the gateway:

Monitoring alarms

On the gateway device, the Alarms tab shows all alarms raised either on the gateway or on the servers.

There are three alarm types which can be raised:

• Connection loss - If the gateway fails to connect to the OPC UA server a critical alarm is raised.
• Gateway crash - If the gateway crashes or is abruptly shut down a major alarm is raised.
• No data arrived within interval - If the status interval check value in the OPC UA server configuration is exceeded a major alarm is raised.

Monitoring alarm details

The following is the full list of monitoring alarms created by the gateway:

Monitoring events

On the gateway device, the Events tab shows all events related to the gateway-server connection. Additionally, you can see when the gateway has started and when it ends.

Monitoring event details

The following is the full list of monitoring events created by the gateway:

Device protocols

Adding a new device protocol

1. In the Device protocols page, click New device protocol in the top menu bar and select OPC UA as device protocol type.

2. In the resulting dialog box, enter a name and an optional description for the device protocol.

3. Optionally, a reference server can be selected. Selecting a reference server allows you to create device protocols based on the OPC UA model stored on an OPC UA server. This greatly simplifies the mapping process, as device protocols can be created based on OPC UA browse paths being actually present on the server.

4. Click Create.
   

Once the device protocol is created, various configuration settings such as variables, data reporting and constraints can be applied. Initially, the device protocol will be inactive. When active, the gateway will scan the address space of all servers and will automatically apply the device protocol to all nodes which match the criteria. When the device protocol is configured, click Save.

Adding a new variable

1. Click Add variable under the Variables section.
2. Enter the path and the name of the variable. The path can be the exact browse path or a regular expression of the browse path. If it is a regular expression, it must be wrapped inside regex(…). For example: regex(2:Objects) or regex(urn:test.namespace:Objects\\d). Note that the namespace index and the namespace URI are not part of the regular expression itself but they will be quoted as literal strings. When using a regular expression, keep in mind that it might be matching many nodes in the address space and resulting in unexpected incoming data. Our recommendation is to use it with great care and together with other exact browse paths in the same mapping if possible. For example, ["2:Objects", "regex(2:MyDevice\\d)", "..."]
3. Select either the default or the custom data reporting. The default option uses the data reporting mechanism used in the device protocol. The custom option will let you configure a data reporting mechanism only for the current variable.
4. Additionally, different functionalities such as sending measurements, creating alarms, sending events and custom actions for each variable can be selected.
5. Click Save to save your settings.

The gateway has a scheduling job and after the variables are saved, the gateway will check whether the variables exist under the subtree of the node. Afterwards, for each node a child device of the server is created. The child devices will contain data based on the configuration of the device protocol. The node child devices will also be listed in the All devices page.

The functionalities that can be enabled are the following:

Send measurement

Turn on Send measurement to specify a measurement.

Specify the following parameters:

• Enter the type of the measurement, for example, “c8y_AccelerationMeasurement”.
• Series are any fragments in measurements that contain a “value” property, for example, “c8y_AccelerationMeasurement.acceleration”.
• Specify the unit of the given measurement, for example, “m/s” for velocity.

All measurements which exceed the Java Long ranges for Long.Max_VALUE(9,223,372,036,854,775,807) or Long.MIN_VALUE(-9,223,372,036,854,775,807) are converted internal to double values with scientific notation (for example 9.223372036854778e+24) to ensure the storage in the database. This may result in a less precise rounded value.

Create alarm

Turn on Create alarm if you want to create an alarm out of the resource.

Specify the following parameters (all mandatory):

• Severity - One of CRITICAL, MAJOR, MINOR, WARNING
• Type
• Text

Send Event

Turn on Send event to send an event each time you receive a resource value.

Specify the following parameters:

• Enter the type of the event, for example, “com_cumulocity_model_DoorSensorEvent”.
• Enter the text which will be sent, for example, “Door sensor was triggered”. You can also get the resource value populated to the event text by defining the value placeholder:

Door sensor was triggered, event value: ${value}

The value will also be populated as a fragment of the created event, under a static fragment name as the following:

{
 "type": "com_cumulocity_model_DoorSensorEvent",
 "text": "Door sensor was triggered",
 "c8y_ua_DataValue": {
     "serverTimestamp": 132403410091850000,
     "sourceTimestamp": 132403410091850000,
     "value": {
         "value": 381632714
     },
     "statusCode": 0
 }
}

The node values under this static fragment that are numeric and exceed the Java long ranges for Long.Max_VALUE(9,223,372,036,854,775,807) or Long.MIN_VALUE(-9,223,372,036,854,775,807) are converted internally to double values with scientific notation (for example 9.223372036854778e+24) to ensure the storage in the database. This may result in a less precise rounded value. However, the node value that is populated for the value placeholder in the event text will have the actual value even if it exceeds the long range.

Custom Actions

Custom actions are HTTP POST requests which the gateway will send to a defined custom URL. You can define custom headers and body template with the following placeholders available:

• ${value}: value of specific node
• ${serverId}: ID of OPC-UA server
• ${nodeId}: ID of source node
• ${deviceId}: ID of source device

Below there is an example of a full device protocol that configures a custom action:

{
   "name": "My device protocol for HttpPost",
   "referencedServerId": "{serverId}",
   "referencedRootNodeId": "ns=2;s=HelloWorld/Dynamic",
   "enabled": true,
   "subscriptionType" : {
     "type": "Subscription",
     "subscriptionParameters": {
       "samplingRate": 1000
     }
   },
   "applyConstraints": {
     "matchesNodeIds": [
       "ns=2;s=HelloWorld/Dynamic1"
     ]
   },
   "mappings": [
       {
           "browsePath": [
               "2:Double"
           ],
           "customAction": {
               "type": "HttpPost",
               "endpoint": "http://my.endpoint.local",
               "bodyTemplate": "{\"text\": \"I am coming from Http POST, value: ${value} \", \"type\": \"HttpPostMO\"}",
               "headers": {
                   "Authorization": "Basic MYAUTHCREDENTIALS==",
                   "Content-Type": "application/json"
               }
           }
       }
   ]
}

Monitoring events for device protocol application

When a device protocol has been applied to or un-applied from a node, a monitoring event is generated as the following:

Device type has been applied

• Event type - c8y_ua_DeviceTypeApplied
• Event text - Device type: {device type ID} is applied to root node: {root node ID} of server: {server ID}
• Event source - The server managed object

Device type has been un-applied

• Event type - c8y_ua_DeviceTypeUnapplied
• Event text -
  • If the device type has been un-applied from all nodes on the server: Device type: {device type ID} is un-applied from all nodes of server: {server ID}
  • If the device type has been un-applied from a specific node on the server: Device type: {device type ID} is un-applied from root node: {root node ID} of server: {server ID}
  • If all device types have been un-applied for the server: All device types are un-applied for server: {server ID}
• Event source - The server managed object

Custom action retry mechanism on external server failure

If a custom action fails, a retry mechanism will be processed. This is configured in the application YAML file, and the queues will be stored in the event repository.

Queues are collections of failed custom actions, including the complete HTTP request of this custom action. Each entry of the queue is one failed custom action.

A background scheduler task will retry each queue up to the number of maxRetries. If maxRetries is reached the queue will be stored as a permanently failed queue in the event repository.

All elements of the queue are retried after the retry delay has passed. In effect, the count of the elements in the queue is decreases with each successful retried custom action.

This mechanism can be configured in the configuration section gateway.mappingExecution.http.failureHandling (see also Additional customization) using the following properties:

Data reporting

There are three data reporting mechanisms which can be applied to read all mapped browse paths:

• None - The gateway will not read values automatically. The mappings will be applied only when manual read operations are performed on mapped nodes.
• Cyclic Read - The gateway reads values from mapped nodes at specified interval rates in milliseconds. The minimum allowed rate is 50 milliseconds.
• Subscription - The gateway retrieves values by using OPC UA’s own subscription mechanism.

Possible parameters:

• Sampling interval (required) - Defines a time interval individually for each mapped node. This is the rate at which the server checks the data source for changes.
• Queue size - The size of the queue where it holds the samples before reporting. If you wish to record samples at a faster rate than reporting interval, you will also need to reserve a longer queue size, to be able to keep all the samples in the server. The reporting interval is defined for the gateway and the value is configurable with the YAML file (see gateway.subscription.reportingRate).
• Discard - Select whether to discard the oldest or the newest item if the samples are exceeding the queue size.
• Data change trigger:
  • Status - Triggers notification if node’s status has changed.
  • Status/Value - Triggers notification if node’s status or value has changed.
  • Status/Value/Timestamp - Triggers notification if node’s status, value or timestamp has changed.
• Deadband filter - Deadband filter makes notified data values to be filtered.
  • None - No filter will be applied. This option is selected by default.
  • Absolute - Contains the absolute change in a data value which causes the generation of a notification. This parameter applies only to variables with any number data type.
  • Percent - The value is defined as the percentage of the EU range. It applies only to analog items with a valid EU range property. This range is multiplied with the deadband value and is then compared to the actual value change in order to determine the need for a data change notification.

Applying constraints

Specifying auto-apply constraints allows you to limit the scope in which the device protocols are applied, for example by specifying a set of possible servers or node IDs. If no constraints are set, device protocols are applied at any fitting location on the OPC UA server.

The following constraints can be applied:

• Limit device protocol to a set of servers - Limit the device protocols to a particular set of servers. This is useful if you want to have 1 device type for each OPC UA server. Simply click on the dropdown menu and select the desired servers.
• Limit device protocol scope in the address space - Limit the scope to servers which have the entered path in their address space.
• Limit device protocol to servers with a certain fragment - The device protocol will only be available to the servers which have the entered fragment.
• Limit device protocol to specific root nodes ID - A list of “root” node IDs (from which your browsePath is defined) to which the device protocol should be applied. For example, if there is only one server and the device protocol is applied to two node IDs, two child devices of the server will be created. Note that if the device protocol variables do not exist in the root nodes, the device protocol will not be applied to the root node server.

Bad StatusCode handling

The gateway creates an alarm with status WARNING for the corresponding OPC UA server managed object when the received DataValue of a node has an abnormal status code (such as BAD or UNCERTAIN). The alarm text in the Cumulocity platform will provide the necessary information such as the node ID, and the StatusCode information (code, value, and description).

The type of the alarm is constructed as c8y_ua_DataValueAbnormal_<nodeId>_<StatusCode>_<value>. This alarm due to the abnormal status code for a node is created once, and the counter is not incremented in the next read operations. The alarm will be cleared by the OPC UA device gateway when the status code is back to normal in the following read operations. The full list of abnormal alarms are stored in the server managed object under the c8y_ua_DataValueAbnormalAlarms fragment.

REST APIs

While the Cumulocity user interface for OPC UA provides an easy and visual way to configure and build your OPC UA solution, the OPC UA management microservice gives you the possibility to do it via RESTful web service.

The full API definitions can be found at /service/opcua-mgmt-service/swagger-ui.html.

OPC UA server resources

Connect a new OPC UA server to the gateway

Endpoint

POST /service/opcua-mgmt-service/gateways/{gatewayId}/servers

Description

Connect a new OPC UA server to the gateway or update the existing server with a new configuration.

Payload

{
    "name": "My Server",
    "config": {
        "securityMode": "NONE",
        "serverUrl": "opc.tcp://127.0.0.1:53530/OPCUA/SimulationServer",
        "autoScanAddressSpace": true
    }
}

Payload data structure explained:

Data structure for ServerConnectionConfig:

alarmStatusMappings example

{
    "alarmStatusMappings": {
        "['0:ActiveState'].text == 'Active' and ['0:AckedState'].text != 'Acknowledged'": "ACTIVE",
        "['0:ActiveState'].text == 'Active' and ['0:AckedState'].text == 'Acknowledged'": "ACKNOWLEDGED",
        "['0:ActiveState'].text == 'Inactive'": "CLEARED",
        "default": "ACTIVE"
    }
}

Alarms status changed by OPC UA server

If events operated on the OPC UA server change their status, these changes can be reflected as internal alarms.

To catch these events and convert them into internal alarms, a UA event mapping with the alarmCreation definition in device protocol and alarmStatusMappings in server configuration are required.

For better performance an in-memory map is used to store the alarm type and the internal representation. These values are also stored on the filesystem and survive a possible crash or restart of the gateway. When the alarm is cleared then its entry is removed from the in-memory map.

The size of the map can be adjusted by several parameters in the configuration file. With maxEntries you can specify the expected number of alarms at the same time, and it is hard-connected with the maxBloatFactor. This factor lets you define a possible maximum of maxEntries to be extended. For example, a default maxEntries value of “100000” and ‘maxBloatFactor’ set to “5.0” results in a maximum of 500000 entries. The avarageKeySize defines the used key size resulting from the length of the type and the external ID. It’s used to calculate the local file size bound to the entry size.

# To avoid many REST calls to the inventory an in-memory map with a crash backup functionality is included.
alarmStatusStore:
  # Expected number of maximum alarms at the same time
  maxEntries: 100000
  # The average size of the keys on the map. Needed for calculation of the size of the database file.
  averageKeySize: 30
  # The number of maxEntries multiplied with this factor results in the real max size of the database file. Resize is done only if needed.
  maxBloatFactor: 5.0

Get all servers of a gateway device

Method

GET /service/opcua-mgmt-service/gateways/{gatewayId}/servers

Parameters

Example response

[
    {
        "id": "25197",
        "gatewayId": "800",
        "name": "My OPC UA server",
        "requiredInterval": 1,
        "config": {
            "securityMode": "NONE",
            "serverUrl": "opc.tcp://127.0.0.1:12686/CumulocityOPCUAServer",
            "userIdentityMode": "Anonymous",
            "timeout": 30,
            "autoReconnect": true,
            "statusCheckInterval": 40,
            "targetConnectionState": "enabled"
        },
        "namespaceTable": [
            "http://opcfoundation.org/UA/",
            "urn:cumulocity:opcua:test:server:ee8ff646-cc83-4a1f-ad29-97356c496ef0",
            "urn:cumulocity:opcua:test:server"
        ],
        "c8y_Availability": {
            "lastMessage": "2020-08-27T12:43:22.585+0000",
            "status": "UNAVAILABLE"
        },
        "c8y_Connection": {
            "status": "DISCONNECTED"
        },
        "c8y_RequiredAvailability": {
            "responseInterval": 1
        }
    }
]

Delete and disconnect an OPC UA server

Endpoint

DELETE /service/opcua-mgmt-service/servers/{serverId}

Description

Delete the OPC UA server managed object. Once the DELETE request is received by the OPC UA management service, the specified server along with all its address space nodes created in the Cumulocity platform will be deleted. The service will retain all the child devices of the server, and their corresponding data, which were created by the device protocols.

Parameters

Response

200 OK

Address space resources

Get an address space node by ID

Endpoint

GET /service/opcua-mgmt-service/servers/{serverId}/address-spaces/get

Description

Get a node in the server address space specified by the given node ID. The node ID must be URL encoded.

Parameters

Example

Endpoint: GET /service/opcua-mgmt-service/servers/10/address-spaces/get?nodeId=i%3D84

{
    "nodeId": "i=84",
    "nodeClass": 1,
    "nodeClassName": "Object",
    "browseName": "0:Root",
    "browsePath": null,
    "displayName": "Root",
    "description": "The root of the server address space.",
    "references": [
        {
            "referenceId": "i=35",
            "targetId": "i=87",
            "referenceLabel": "Organizes",
            "targetLabel": "Views",
            "targetBrowseName": "Views",
            "inverse": false,
            "hierarchical": true
        },
        {
            "referenceId": "i=40",
            "targetId": "i=61",
            "referenceLabel": "HasTypeDefinition",
            "targetLabel": "FolderType",
            "targetBrowseName": "FolderType",
            "inverse": false,
            "hierarchical": false
        }
    ],
    "attributes": {
        "eventNotifier": 0
    },
    "absolutePaths": [
        [
            "0:Root"
        ]
    ],
    "ancestorNodeIds": [
        []
    ]
}

Get children of a given node

Endpoint

GET /service/opcua-mgmt-service/servers/{serverId}/address-spaces/children

Description

Get all child nodes of the given node specified by the node ID in the server address space. The node ID must be properly URL encoded.

Parameters

Example

Endpoint: GET /service/opcua-mgmt-service/servers/10/address-spaces/children?nodeId=i%3D84

[
    {
        "nodeId": "i=86",
        "nodeClass": 1,
        "nodeClassName": "Object",
        "browseName": "0:Types",
        "browsePath": null,
        "displayName": "Types",
        "description": "The browse entry point when looking for types in the server address space.",
        "references": [
            {
                "referenceId": "i=40",
                "targetId": "i=61",
                "referenceLabel": "HasTypeDefinition",
                "targetLabel": "FolderType",
                "targetBrowseName": "FolderType",
                "inverse": false,
                "hierarchical": false
            },
            {
                "referenceId": "i=35",
                "targetId": "i=86",
                "referenceLabel": "OrganizedBy",
                "targetLabel": "Types",
                "targetBrowseName": "Types",
                "inverse": true,
                "hierarchical": true
            }
        ],
        "attributes": {
            "eventNotifier": 0
        },
        "absolutePaths": [
            [
                "0:Root",
                "0:Types"
            ]
        ],
        "ancestorNodeIds": [
            [
                "i=84"
            ]
        ]
    }
]

Browse a node

Endpoint

GET /service/opcua-mgmt-service/servers/{serverId}/address-spaces/browse

Description

Browse a node from a base node following the given browse path. This basically searches for a node with relative browse path to the other node.

Parameters

Example

Endpoint: GET /service/opcua-mgmt-service/servers/10/address-spaces/browse?nodeId=i%3D84&browsePath=Objects

[
    {
        "nodeId": "i=85",
        "nodeClass": 1,
        "nodeClassName": "Object",
        "browseName": "0:Objects",
        "browsePath": null,
        "displayName": "Objects",
        "description": "The browse entry point when looking for objects in the server address space.",
        "references": [
            {
                "referenceId": "i=35",
                "targetId": "i=2253",
                "referenceLabel": "Organizes",
                "targetLabel": "Server",
                "targetBrowseName": "Server",
                "inverse": false,
                "hierarchical": true
            },
            {
                "referenceId": "i=35",
                "targetId": "ns=2;s=Cumulocity",
                "referenceLabel": "Organizes",
                "targetLabel": "Cumulocity",
                "targetBrowseName": "2:Cumulocity",
                "inverse": false,
                "hierarchical": true
            }
        ],
        "attributes": {
            "eventNotifier": 0
        },
        "absolutePaths": [
            [
                "0:Root",
                "0:Objects"
            ]
        ],
        "ancestorNodeIds": [
            [
                "i=84"
            ]
        ]
    }
]

Device type resources

These resources provide the APIs for manipulating device types.

Creating a new device type

Endpoint

POST /service/opcua-mgmt-service/device-types

Sample payloads

• Measurement mappings using subscription

  {
      "name": "My device type",
      "enabled": true,
      "mappings": [
          {
              "browsePath": [
                  "2:Dynamic",
                  "2:Double"
              ],
              "measurementCreation": {
                  "unit": "T",
                  "type": "MyMeasurementType",
                  "fragmentName": "MyMeasurement",
                  "series": "MySeries"
              }
          }
      ],
      "subscriptionType": {
          "type": "Subscription",
          "subscriptionParameters": {
              "samplingRate": 5000
          }
      }
  }
  

• Event mappings using cyclic read

  {
      "name": "My device type",
      "enabled": true,
      "mappings": [
          {
              "browsePath": [
                  "2:Dynamic",
                  "2:Integer"
              ],
              "eventCreation": {
                  "type": "MyEventType",
                  "text": "My event with value ${value}"
              }
          }
      ],
      "subscriptionType": {
          "type": "Cyclicread",
          "rate": 5000
      }
  }
  

• Alarm mappings using subscription

  {
      "name": "My device type",
      "enabled": true,
      "mappings": [
          {
              "browsePath": [
                  "2:Dynamic",
                  "2:Boolean"
              ],
              "alarmCreation": {
                  "type": "MyAlarm",
                  "severity": "MAJOR",
                  "text": "Heads up, the level is high!"
              }
          }
      ],
      "subscriptionType": {
          "type": "Subscription",
          "subscriptionParameters": {
              "samplingRate": 5000
          }
      }
  }
  

• UA events mappings into alarm and event

  {
      "name": "My device type",
      "enabled": true,
      "uaEventMappings": [
          {
              "browsePath": [
                  "Server"
              ],
              "eventTypeId": "i=2041",
              "attributes": [
                  "Message",
                  "Severity"
              ],
              "alarmCreation": {
                  "text": "ALARM! message: ${0}",
                  "severity": "MAJOR",
                  "status": "ACTIVE",
                  "type": "c8y_myEvent_alarm_${1}"
              }
          }
      ]
  }
  

Full payload data structure explained:

Data structure for Mapping

Data structure for UAMapping

Data structure for SubscriptionType

Data structure for OverriddenSubscription

Data structure for ApplyConstraints

Data structure for MeasurementCreation

Data structure for EventCreation

Data structure for AlarmCreation

Data structure for HttpPostAction

Data structure for UAEventCreation

This has exactly the same fields as EventCreation, however the text and type field can be parameterized with different parameters.

Data structure for UAAlarmCreation

Data structure for SubscriptionParameter

Data structure for CyclicParameter

Data structure for ServerNodeValues

Data structure for MatchingNode

Get all OPC UA device types

Endpoint

GET /service/opcua-mgmt-service/device-types

Payload

The endpoint returns a JSON array of all OPC UA device types.

Get a single device type

Endpoint

GET /service/opcua-mgmt-service/device-types/{deviceTypeId}

Payload

A JSON representation of the device type with the given ID if it exists. If not, an error message is returned.

Response codes

200 OK

404 Not found

Updating a device type

Endpoint

PUT /service/opcua-mgmt-service/device-types/{deviceTypeId}

Payload

The payload of updating a device type is exactly the same as the payload of creating it. Please note that partial update is not supported. All information must be provided in the update request and will completely override the existing device type.

Deleting a device type

Endpoint

DELETE /service/opcua-mgmt-service/device-types/{deviceTypeId}

Success response

204 No Content

Operations

Cumulocity operations is the interface that is used to tell the gateway what to do and how to do it. This section describes all operations that are currently supported by the gateway.

Scanning the address space

This operation triggers importing address space for a specific OPC-UA server. The server’s ID is passed as a device ID. The gateway will scan the entire address space of the server and persist a twinned representation of the address space in the Cumulocity platform.

POST /devicecontrol/operations/

{
    "deviceId": "<server-device-Id>",
    "c8y_ua_command_ScanAddressSpace": {
            "skipSync": false
    },
    "description": "Import address space from root node"
}

The twinned address space information is persisted in the Cumulocity inventory. It is internally used to support address space browsing and to define device protocols. Hence this operation is always triggered if a new server is added to the platform.

Once the device gateway knows the address space, it uses it to handle different logics, for example applying device protocols to nodes. So if you already have the address space scanned once and stored in Cumulocity, you might want the device gateway to learn one more time about server’s address space without synchronizing data into Cumulocity. To achieve that, provide "skipSync": true.

When you would like to scan partial address space, you can provide the nodeId property which is used as a start node for the scan operation. The subaddress space starting from this node as well as the ancestor nodes will be persisted in the Cumulocity inventory (unless "skipSync": true is provided) as well as in the local address space file of the gateway.

POST /devicecontrol/operations/

{
    "deviceId": "<server-device-Id>",
    "c8y_ua_command_ScanAddressSpace": {
            "nodeId":"ns=2;s=MyDevice"
    },
    "description": "Import address space from MyDevice node"
}

Available arguments for c8y_ua_command_ScanAddressSpace:

Reading the value of a node/nodes

This operation reads the value attribute of specific node or list of nodes. The deviceId of the operation can be either the OPC UA Server device ID or the generated device ID (child device of OPC UA Server).

POST /devicecontrol/operations/

{
    "deviceId" : "<server-or-child-device-Id>",
    "c8y_ua_command_ReadValue": {
     "nodes": ["NODE_ID"],
     "timestampsToReturn": "Neither"
    },
    "description":"read value"
}

Available arguments for c8y_ua_command_ReadValue:

    NumericRange: <dimension> [',' <dimension>]
    <dimension>: <index> [':' <index>]

The result of this operation will contain output in the following format:

{
    "results": {
        "ns=2;s=MyLevel": {
            "13": {
                "value": {
                    "value": 77.0
                },
                "statusCode": 0,
                "sourcePicoseconds": 0,
                "serverPicoseconds": 0
            }
        }
    }
}

Reading all attributes of a node

This operation returns all attributes of specific node. The deviceId of the operation can be either the OPC UA Server device ID or the generated device ID (child device of OPC UA Server).

{
    "deviceId": "<server-or-child-device-Id>",
    "c8y_ua_command_ReadNodeAttributes": {
        "node": "ns=2;s=MyEnumObject"
    },
    "description": "Read node attributes"
}

Available arguments for c8y_ua_command_ReadNodeAttributes:

The result may differ depending on the node type.

{
    "Value": {
        "value": 1
    },
    "DataType": "ns=2;s=MyEnumType",
    "ValueRank": -1,
    "AccessLevel": 3,
    "UserAccessLevel": 3,
    "MinimumSamplingInterval": -1.0,
    "Historizing": false,
    "DisplayName": "MyEnumObject",
    "WriteMask": 0,
    "UserWriteMask": 0
}

Reading an attribute

This operation supports to read one or more attributes of one or more nodes. This includes support of the range parameter to read a single element or a range of elements when the attribute value is an array. The deviceId of the operation can be either the OPC UA Server device ID or the generated device ID (child device of OPC UA Server).

{
    "deviceId": "<server-or-child-device-Id>",
    "c8y_ua_command_ReadAttribute": {
         "nodes": ["ns=3;s=FloatArray"],
         "attribute":"13"
    },
    "description": "Read attribute from ns=3;s=FloatArray"
}

Available arguments for c8y_ua_command_ReadAttribute:

    NumericRange: <dimension> [',' <dimension>]
    <dimension>: <index> [':' <index>]

The result may differ depending on the node type.

{
    "results": {
        "ns=3;s=FloatArray": {
            "13": {
                "value": {
                    "value": [1.0, 2.0, 3.0, 4.0, 5.0]
                },
                "statusCode": 0,
                "sourceTimestamp": 1566572540173,
                "sourcePicoseconds": 0,
                "serverTimestamp": 1566573849897,
                "serverPicoseconds": 0
            }
        }
    }
}

Example operation with ranges fragment:

{
    "description": "Read attribute from ns=3;s=FloatArray",
    "deviceId": "<server-device-Id>",
    "c8y_ua_command_ReadAttribute": {
         "nodes": ["ns=3;s=FloatArray"],
         "attribute":"13",
         "ranges":"0:1"
    }
}

The result may differ depending on the node type.

{
    "results": {
        "ns=3;s=FloatArray": {
            "13": {
                "value": {
                    "value": [1.0, 2.0]
                },
                "statusCode": 0,
                "sourceTimestamp": 1566572540173,
                "sourcePicoseconds": 0,
                "serverTimestamp": 1566574513935,
                "serverPicoseconds": 0
            }
        }
    }
}

Read complex

This operation reads many attributes from many nodes at single call. The deviceId of the operation can be either the OPC UA Server device ID or the generated device ID (child device of OPC UA Server).

{
  "deviceId" : "<server-or-child-device-Id>",
  "c8y_ua_command_ReadComplex": {
       "nodeAttrs": {
         "ns=2;s=MyEnumObject": {
           "13":"",
           "11":""
         }
       }
  },
  "description":"Read complex"
}

Available arguments for c8y_ua_command_ReadComplex:

    NumericRange: <dimension> [',' <dimension>]
    <dimension>: <index> [':' <index>]

Historic read

This operation reads history values and applies the mappings except of alarm mappings. The deviceId of the operation can be either the OPC UA Server device ID or the generated device ID (child device of OPC UA Server).

{
    "deviceId": "<server-or-child-device-Id>",
    "c8y_ua_command_HistoricReadOperation": {
        "nodeId": "ns=2;s=MyLevel",
        "processMappings": true,
        "dateFrom": "2019-06-13T10:43:00+02:00",
        "dateTo": "2019-06-13T10:52:00+02:00",
        "tagType": "TAG",
        "batchSize": 500
    },
    "description": "Historic read"
}

Available arguments for c8y_ua_command_HistoricReadOperation:

    NumericRange: <dimension> [',' <dimension>]
    <dimension>: <index> [':' <index>]

Historic data binary upload

This operation reads historic values and only saves those values to a file which can be retrieved using the binary API. The deviceId of the operation can be either the OPC UA Server device ID or the generated device ID (child device of OPC UA Server).

{
    "deviceId": "<server-or-child-device-Id>",
    "c8y_ua_command_HistoricDataUploadOperation": {
        "nodeId": "ns=2;s=MyLevel",
        "dateFrom": "2019-01-03T09:53:00+02:00",
        "dateTo": "2019-06-13T18:53:00+02:00",
        "chunkSize": 1,
        "compress": true,
        "batchSize": 150000
    },
    "description": "Upload history data"
}

The binary file representations, which can be queried using binary API, are created with the type “c8y_ua_HistoricData” and an operationId with the value of the operation with which it has been generated.

Available arguments for c8y_ua_command_HistoricDataUploadOperation:

    NumericRange: <dimension> [',' <dimension>]
    <dimension>: <index> [':' <index>]

Read file

Prerequisites:

• Open and Read methods for the file node must be implemented on server side, either as the children of the file node itself or as the children of the data type node

With this operation, a file can be downloaded from the OPC UA server at the given fileNodeId. The deviceId of the operation can be either the OPC UA Server device ID or the generated device ID (child device of OPC UA Server).

{
  "deviceId" : "<server-or-child-device-Id>",
  "c8y_ua_command_ReadFileOperation": {
    "fileNodeId": "ns=2;s=sampleFile",
    "bufferSize": <bufferSize>
  },
  "description":"Read sample file"
}

Available arguments for c8y_ua_command_ReadFileOperation:

After the downloaded file has been read successfully (see Control tab of the device) it is available in Management > Files repository in the Administration application for download to local file system.

Alternatively, you can check the binary folder by using the binary API like this:

{{url}}/inventory/binaries

This returns a JSON response like this:

{
  "self": "http://<tenant-domain>/inventory/binaries?pageSize=5&currentPage=1",
  "managedObjects": [
    {
      "owner": <device-owner>,
      "type": "ua-file-type",
      "lastUpdated": "2021-05-17T14:33:21.074Z",
      "name": "ns=2;s=sampleFile",
      "self": "http://<tenant-domain>/inventory/binaries/2351",
      "id": "2351",
      "c8y_IsBinary": "",
      "length": 13268,
      "contentType": "application/octet-stream"
    }
  ],
  "statistics": {
    "totalPages": 1,
    "currentPage": 1,
    "pageSize": 5
  }
}

Now download is possible with the self link provided inside the managedObjects section of the JSON response.

For further information, refer to binaries API in the Cumulocity OpenAPI Specification.

Write value

This operation writes values to the node/nodes. The deviceId of the operation can be either the OPC UA Server device ID or the generated device ID (child device of OPC UA Server).

{
    "deviceId": "<server-or-child-device-Id>",
    "c8y_ua_command_WriteValue": {
        "values": {
            "ns=3;s=LocalizedText": {
                "value": "This is a localized text"
            },
            "ns=3;s=Double": {
                "value": "3.14159"
            }
        }
    },
    "description": "Write values to different nodes"
}

Available arguments for c8y_ua_command_WriteValue:

Available arguments for type rangedValue (used as map value in c8y_ua_command_WriteValue.values):

    NumericRange: <dimension> [',' <dimension>]
    <dimension>: <index> [':' <index>]

Write attribute

This operation is similar to the previous one, but instead of writing to the value attribute, this operation writes attributes’ values to any writable attributes. The following example writes two different attributes to two different nodes. The deviceId of the operation can be either the OPC UA Server device ID or the generated device ID (child device of OPC UA Server).

{
    "deviceId": "<server-or-child-device-Id>",
    "c8y_ua_command_WriteAttribute": {
        "values": {
            "ns=3;s=LocalizedText": {
                "attribute": "13",
                "value": "This is a localized text"
            },
            "ns=3;s=Double": {
                "attribute": "13",
                "value": "3.14159"
            }
        }
    },
    "description": "Write attributes' values to different attributes of different nodes"
}

Available arguments for c8y_ua_command_WriteAttribute:

Available arguments for type attributeRangedValue (used as map value in c8y_ua_command_WriteAttribute.values):

    NumericRange: <dimension> [',' <dimension>]
    <dimension>: <index> [':' <index>]

Example operation with ranges fragment:

{
    "deviceId": "<server-device-Id>",
    "c8y_ua_command_WriteAttribute": {
        "values": {
            "ns=3;s=FloatArray": {
                "attribute": "13",
                "ranges": "0:1",
                "value": "2.0,4.0"
            }
        }
    },
    "description": "Write attribute value to array attribute"
}

Get method description

This operation reads the description of a method node. The deviceId of the operation can be either the OPC UA Server device ID or the generated device ID (child device of OPC UA Server).

{
    "deviceId": "<server-or-child-device-Id>",
    "c8y_ua_command_GetMethodDescriptionOperation": {
        "nodeId": "ns=2;s=MyMethod"
    },
    "description": "get method description"
}

Available arguments for c8y_ua_command_GetMethodDescriptionOperation:

The result describes a method, it’s parent object, input and output arguments.

{
    "nodeId": "ns=2;s=MyMethod",
    "name": "MyMethod",
    "parentNodeId": "ns=2;s=MyDevice",
    "parentName": "MyDevice",
    "inputArguments": [{
            "name": "Operation",
            "description": "The operation to perform on parameter: valid functions are sin, cos, tan, pow",
            "dataType": "String",
            "dataTypeId": "i=12"
        },
        {
            "name": "Parameter",
            "description": "The parameter for operation",
            "dataType": "Double",
            "dataTypeId": "i=11"
        }
    ],
    "outputArguments": [{
        "name": "Result",
        "description": "The result of 'operation(parameter)'",
        "dataType": "Double",
        "dataTypeId": "i=11"
    }]
}

Call method

This operation calls the method on the OPC UA server. It requires complete input arguments with an additional “value” fragment. The deviceId of the operation can be either the OPC UA Server device ID or the generated device ID (child device of OPC UA Server).

{
    "deviceId": "<server-or-child-device-Id>",
    "c8y_ua_command_CallMethodOperation": {
        "request": {
            "nodeId": "ns=2;s=MyMethod",
            "arguments": [{
                    "name": "Operation",
                    "description": "The operation to perform on parameter: valid functions are sin, cos, tan, pow",
                    "dataType": "String",
                    "dataTypeId": "i=12",
                    "value": "pow"
                },
                {
                    "name": "Parameter",
                    "description": "The parameter for operation",
                    "dataType": "Double",
                    "dataTypeId": "i=11",
                    "value": "5"
                }
            ]
        }
    },
    "description": "call method"
}

Available arguments for c8y_ua_command_CallMethodOperation:

Available arguments for type methodRequest (used in c8y_ua_command_CallMethodOperation.request):

Available arguments for type methodArgument (used in c8y_ua_command_CallMethodOperation.request.arguments):

The result contains all output arguments with values set by the OPC UA server. Power of 5 is 25:

{
    "statusCode": 0,
    "result": [{
        "name": "Result",
        "description": "The result of 'operation(parameter)'",
        "dataType": "Double",
        "dataTypeId": "i=11",
        "value": "25.0"
    }]
}

Testing a device type against a node on an OPC UA server

This operation allows for testing a device type against a specific node on an OPC UA server. The operation result provides diagnostic information if the device type could be applied:

{
   "deviceId":"<server-device-Id>",
   "c8y_ua_command_TestDeviceTypeMatching":{
      "deviceTypeId":"<device-type-id>",
      "rootNodeId":"<node-id>"
   },
   "description":"Test Device Type"
}

Available arguments for c8y_ua_command_TestDeviceTypeMatching:

If the device type can be applied to the given node, the operation result confirms this:

{
   "creationTime":"2020-08-20T12:28:57.973Z",
   "deviceId":"12789",
   "deviceName":"Test Server",
   "id":"15478",
   "status":"SUCCESSFUL",
   "c8y_ua_command_TestDeviceTypeMatching":{
      "deviceTypeId":"14989",
      "rootNodeId":"nsu=urn:cumulocity:opcua:test:server;s=HelloWorld/Dynamic2"
   },
   "c8y_Command":{
      "result":"{\n  \"matches\": true\n}"
   },
   "description":"Test Device Type"
}

Otherwise, the operation result provides an explanation why the device type could not be matched to the given root node:

{
   "creationTime":"2020-08-20T12:34:01.524Z",
   "deviceId":"12789",
   "deviceName":"Milo Reloaded",
   "id":"15688",
   "status":"SUCCESSFUL",
   "c8y_ua_command_TestDeviceTypeMatching":{
      "deviceTypeId":"14989",
      "rootNodeId":"nsu=urn:cumulocity:opcua:test:server;s=HelloWorld/Dynamic9"
   },
   "c8y_Command":{
      "result":"{\n  \"matches\": false,\n  \"reason\": \"Does not match browse path regex constraint, constraints: (.*Dynamic[1-3]), actual: [[http://opcfoundation.org/UA/:Root, http://opcfoundation.org/UA/:Objects, urn:cumulocity:opcua:test:server:Dynamic Playground, urn:cumulocity:opcua:test:server:Dynamic9]]\"\n}",
      "syntax":null,
      "text":null
   },
   "description":"Test Device Type"
}

Analyzing the set of nodes to which a device type can be applied (dry run)

As explained earlier, the Cumulocity OPC UA gateway performs an auto-discovery to determine the set of nodes that match a certain device protocol (“device type”). The following operation performs an auto-discovery for the given device protocol on the server, without actually applying it to any node (“dry run”):

{
   "deviceId":"<server-device-Id>",
   "c8y_ua_command_DryRunDeviceTypeMatching":{
      "deviceTypeId":"<device-type-id>"
   },
   "description":"Dry Run Device Type"
}

Available arguments for c8y_ua_command_DryRunDeviceTypeMatching:

The result of the operation contains the set of nodes that match the device protocol. In addition to that, the fragment matchednodes is added to the operation. It contains a JSON representation of the matched nodes.

{
   "creationTime":"2020-08-20T12:22:07.947Z",
   "deviceId":"12789",
   "deviceName":"Test Server",
   "id":"15187",
   "status":"SUCCESSFUL",
   "c8y_Command":{
      "result":"Device protocol is currently disabled. Device protocol would be applied to the following nodes: [\n  {\n    \"nodeId\": \"nsu=urn:cumulocity:opcua:test:server;s=HelloWorld/Dynamic2\",\n    \"deviceTypeId\": \"14989\",\n    \"mappedTargetNodes\": [\n      {\n        \"browsePath\": [\n          \"urn:cumulocity:opcua:test:server:Double\"\n        ],\n        \"targetNodeId\": \"nsu=urn:cumulocity:opcua:test:server;s=HelloWorld/Dynamic/Double2\"\n      }\n    ],\n    \"attrs\": {}\n  },\n  {\n    \"nodeId\": \"nsu=urn:cumulocity:opcua:test:server;s=HelloWorld/Dynamic1\",\n    \"deviceTypeId\": \"14989\",\n    \"mappedTargetNodes\": [\n      {\n        \"browsePath\": [\n          \"urn:cumulocity:opcua:test:server:Double\"\n        ],\n        \"targetNodeId\": \"nsu=urn:cumulocity:opcua:test:server;s=HelloWorld/Dynamic/Double1\"\n      }\n    ],\n    \"attrs\": {}\n  },\n  {\n    \"nodeId\": \"nsu=urn:cumulocity:opcua:test:server;s=HelloWorld/Dynamic3\",\n    \"deviceTypeId\": \"14989\",\n    \"mappedTargetNodes\": [\n      {\n        \"browsePath\": [\n          \"urn:cumulocity:opcua:test:server:Double\"\n        ],\n        \"targetNodeId\": \"nsu=urn:cumulocity:opcua:test:server;s=HelloWorld/Dynamic/Double3\"\n      }\n    ],\n    \"attrs\": {}\n  }\n]",
      "matchedNodes":[
         {
            "mappedTargetNodes":[
               {
                  "targetNodeId":"nsu=urn:cumulocity:opcua:test:server;s=HelloWorld/Dynamic/Double2",
                  "browsePath":[
                     "urn:cumulocity:opcua:test:server:Double"
                  ]
               }
            ],
            "deviceTypeId":"14989",
            "nodeId":"nsu=urn:cumulocity:opcua:test:server;s=HelloWorld/Dynamic2"
         },
         {
            "mappedTargetNodes":[
               {
                  "targetNodeId":"nsu=urn:cumulocity:opcua:test:server;s=HelloWorld/Dynamic/Double1",
                  "browsePath":[
                     "urn:cumulocity:opcua:test:server:Double"
                  ]
               }
            ],
            "deviceTypeId":"14989",
            "nodeId":"nsu=urn:cumulocity:opcua:test:server;s=HelloWorld/Dynamic1"
         },
         {
            "mappedTargetNodes":[
               {
                  "targetNodeId":"nsu=urn:cumulocity:opcua:test:server;s=HelloWorld/Dynamic/Double3",
                  "browsePath":[
                     "urn:cumulocity:opcua:test:server:Double"
                  ]
               }
            ],
            "deviceTypeId":"14989",
            "nodeId":"nsu=urn:cumulocity:opcua:test:server;s=HelloWorld/Dynamic3"
         }
      ],
      "syntax":null,
      "text":null
   },
   "description":"Dry Run Device Type",
   "c8y_ua_command_DryRunDeviceTypeMatching":{
      "deviceTypeId":"14989"
   }
}

Get the current application state of a device type

In order to know what is the current state of a device type application, use the following operation:

{
	"description": "Get device type application state",
	"deviceId": "{server-device-Id}",
	"c8y_ua_command_GetDeviceTypeApplicationState": {
		"deviceTypeId": "{device protocol ID}",
		"matchingRootNodes": ["{root node ID #1}", "{root node ID #2}"]
	}
}

Available arguments for c8y_ua_command_GetDeviceTypeApplicationState:

The result will be populated into the operation result as a map of nodes telling whether the device type has been applied to that node or not.

Sample result when the device type has been applied to node #1 but not node #2:

{
    "{root node ID #1}": true,
    "{root node ID #2}": false
}

Expiring operations

In certain cases it is desirable that the OPC UA gateway executes an operation only if it processes it before a given expiration time. Providing such an optional expiration time is supported for the following OPC UA operations:

• Reading the value of a node/nodes
• Reading all attributes of a node
• Reading an attribute
• Read complex
• Write value
• Write attribute
• Call method

For all the given operations this expiry mechanism can be activated by supplying an expirationTime fragment inside the operation body.

The following example shows how to mark a read operation as expiring:

{
  "deviceId" : "<server-device-Id>",
  "c8y_ua_command_ReadValue": {
    "nodes": ["ns=3;s=FloatArray"],
    "expirationTime": "2021-02-08T15:00:00.000Z"
  },
  "description":"Expiring read value"
}

The operation above will only perform a read on the OPC UA server if processed by the gateway before the 8th of February, 2021 15:00. Otherwise, the operation will fail. In this case, Operation expired is returned as failure reason.

OPC UA events

Model change events

The model change events are created by the OPC UA server to notify about the changes in an address space node on runtime. The gateway subscribes to the events of type BaseModelChangeEventType on connection to the servers. The subscription to this event can be enabled or disabled for each server using the subscribeModelChangeEvent property during the server configuration. The changes for the events with type GeneralModelChangeEventType and SemanticChangeEventType, which are subtypes of BaseModelChangeEventType, are handled and address space information is persisted in the Cumulocity inventory as well as in the local address space file of the gateway.

Troubleshooting

Permission denied error when running the gateway JAR file on a Linux OS

If the following error appears, add a baseDir property to the YAML file. For example:

db:
  baseDir: ${user.home}/.opcua/profile/data

Unknown host exception when running the gateway JAR

This error appears if the provided baseUrl property in the YAML file is incorrect.

Failed to load property source from location when running the gateway JAR

The following error appears if the indentation of the properties in the YAML file is incorrect.

java.net.BindException: Address already in use

If this error appears, a Java process is running in the background. To fix this issue, the process must be stopped/killed.

Changing the log level for troubleshooting

For troubleshooting purposes, we recommend you to enable the DEBUG log level for subpackages and root if required, and send the log file to product support.

For example:

    <logger name="com.cumulocity.opcua.client.gateway" level="DEBUG"/>
    <logger name="com.cumulocity" level="DEBUG"/>
    <logger name="c8y" level="DEBUG"/>

    <root level="DEBUG">
        <appender-ref ref="FILE" />
        <appender-ref ref="STDOUT"/>
    </root>

If there is an unknown error during the address space scans, enable DEBUG or TRACE log level specifically for the scanners:

    <logger name="com.cumulocity.opcua.client.BaseAddressSpaceScanner" level="DEBUG" />
    <logger name="com.cumulocity.opcua.client.OpcuaAddressSpaceFullScanner" level="DEBUG" />
    <logger name="com.cumulocity.opcua.client.OpcuaAddressSpaceLightScanner" level="DEBUG" />
    <logger name="com.cumulocity.opcua.client.OpcuaAddressSpaceReverseFullScanner" level="DEBUG" />

    <root level="INFO">
        <appender-ref ref="FILE" />
        <appender-ref ref="STDOUT"/>
    </root>

For additional information about log levels, refer to the Logback architecture documentation.

Java Management Extensions (JMX)

For additional monitoring, the gateway component provides MBeans. These MBeans get exposed if the following configuration is set in the application.yaml file:

spring:
     jmx:
         enabled: true

Via jconsole the MBeans can be selected and the following attributes can be accessed:

It can be useful to get some statistics for custom actions in particular. These attributes can be retrieved from the CustomActionMBean:

1. Table of all called URLs seperated by HTTP return code and retry count.

   

   The key entry of the table consists of:

   {URL}_{HTTP Response Code}_{Retry Count}
   

2. If retry is enabled, the queue size of the retry queue can be monitored.