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Properties of the IoT Edge agent and IoT Edge hub module twins

Applies to: IoT Edge 1.5 checkmark IoT Edge 1.5 IoT Edge 1.4 checkmark IoT Edge 1.4

Important

IoT Edge 1.5 LTS and IoT Edge 1.4 LTS are supported releases. IoT Edge 1.4 LTS is end of life on November 12, 2024. If you are on an earlier release, see Update IoT Edge.

The IoT Edge agent and IoT Edge hub are two modules that make up the IoT Edge runtime. For more information about the responsibilities of each runtime module, see Understand the Azure IoT Edge runtime and its architecture.

This article provides the desired properties and reported properties of the runtime module twins. For more information on how to deploy modules on IoT Edge devices, see Learn how to deploy modules and establish routes in IoT Edge.

A module twin includes:

  • Desired properties. The solution backend can set desired properties, and the module can read them. The module can also receive notifications of changes in the desired properties. Desired properties are used along with reported properties to synchronize module configuration or conditions.

  • Reported properties. The module can set reported properties, and the solution backend can read and query them. Reported properties are used along with desired properties to synchronize module configuration or conditions.

EdgeAgent desired properties

The module twin for the IoT Edge agent is called $edgeAgent and coordinates the communications between the IoT Edge agent running on a device and IoT Hub. The desired properties are set when applying a deployment manifest on a specific device as part of a single-device or at-scale deployment.

Property Description Required
imagePullPolicy When to pull the image in either OnCreate or Never (Never can be used if the image is already on the device) Yes
restartPolicy When the module should be restarted. Possible values are: Never: don't restart module if not running, Always: always restart module if not running, On-Unhealthy: restart module if unhealthy. Unhealthy is what Docker reports based on a health check, for example "Unhealthy - the container is not working correctly", On-Failed: restart if Failed. Yes
runtime.type Has to be docker. Yes
runtime.settings.minDockerVersion Set to the minimum Docker version required by this deployment manifest. Yes
runtime.settings.loggingOptions A stringified JSON containing the logging options for the IoT Edge agent container. Docker logging options No
runtime.settings.registryCredentials.{registryId}.username The username of the container registry. For Azure Container Registry, the username is usually the registry name. Registry credentials are necessary for any private module images. No
runtime.settings.registryCredentials.{registryId}.password The password for the container registry. No
runtime.settings.registryCredentials.{registryId}.address The address of the container registry. For Azure Container Registry, the address is usually {registry name}.azurecr.io. No
schemaVersion Either 1.0 or 1.1. Version 1.1 was introduced with IoT Edge version 1.0.10, and is recommended. Yes
status Desired status of the module: Running or Stopped. Required
systemModules.edgeAgent.type Has to be docker. Yes
systemModules.edgeAgent.startupOrder An integer value for the location a module has in the startup order. A 0 is first and max integer (4294967295) is last. If a value isn't provided, the default is max integer. No
systemModules.edgeAgent.settings.image The URI of the image of the IoT Edge agent. Currently, the IoT Edge agent isn't able to update itself. Yes
systemModules.edgeAgent.settings.createOptions A stringified JSON containing the options for the creation of the IoT Edge agent container. Docker create options No
systemModules.edgeAgent.configuration.id The ID of the deployment that deployed this module. IoT Hub sets this property when the manifest is applied using a deployment. Not part of a deployment manifest.
systemModules.edgeHub.type Has to be docker. Yes
systemModules.edgeHub.status Has to be running. Yes
systemModules.edgeHub.restartPolicy Has to be always. Yes
systemModules.edgeHub.startupOrder An integer value for which spot a module has in the startup order. A 0 is first and max integer (4294967295) is last. If a value isn't provided, the default is max integer. No
systemModules.edgeHub.settings.image The URI of the image of the IoT Edge hub. Yes
systemModules.edgeHub.settings.createOptions A stringified JSON containing the options for the creation of the IoT Edge hub container. Docker create options No
systemModules.edgeHub.configuration.id The ID of the deployment that deployed this module. IoT Hub sets this property when the manifest is applied using a deployment. Not part of a deployment manifest.
modules.{moduleId}.version A user-defined string representing the version of this module. Yes
modules.{moduleId}.type Has to be docker. Yes
modules.{moduleId}.status {running | stopped} Yes
modules.{moduleId}.restartPolicy {never | always} Yes
modules.{moduleId}.startupOrder An integer value for the location a module has in the startup order. A 0 is first and max integer (4294967295) is last. If a value isn't provided, the default is max integer. No
modules.{moduleId}.imagePullPolicy {on-create | never} No
modules.{moduleId}.env A list of environment variables to pass to the module. Takes the format "<name>": {"value": "<value>"}. No
modules.{moduleId}.settings.image The URI to the module image. Yes
modules.{moduleId}.settings.createOptions A stringified JSON containing the options for the creation of the module container. Docker create options No
modules.{moduleId}.configuration.id The ID of the deployment that deployed this module. IoT Hub sets this property when the manifest is applied using a deployment. Not part of a deployment manifest.
version The current iteration that has version, commit, and build. No

EdgeAgent reported properties

The IoT Edge agent reported properties include three main pieces of information:

  1. The status of the application of the last-seen desired properties;
  2. The status of the modules currently running on the device, as reported by the IoT Edge agent; and
  3. A copy of the desired properties currently running on the device.

The copy of the current desired properties is useful to tell whether the device has applied the latest deployment or is still running a previous deployment manifest.

Note

The reported properties of the IoT Edge agent are useful as they can be queried with the IoT Hub query language to investigate the status of deployments at scale. For more information on how to use the IoT Edge agent properties for status, see Understand IoT Edge deployments for single devices or at scale.

The following table does not include the information that is copied from the desired properties.

Property Description
lastDesiredStatus.code This status code refers to the last desired properties seen by the IoT Edge agent. Allowed values: 200 Success, 400 Invalid configuration, 412 Invalid schema version, 417 Desired properties are empty, 500 Failed.
lastDesiredStatus.description Text description of the status.
lastDesiredVersion This integer refers to the last version of the desired properties processed by the IoT Edge agent.
runtime.platform.OS Reporting the OS running on the device.
runtime.platform.architecture Reporting the architecture of the CPU on the device.
schemaVersion Schema version of reported properties.
systemModules.edgeAgent.runtimeStatus The reported status of IoT Edge agent: {running | unhealthy}.
systemModules.edgeAgent.statusDescription Text description of the reported status of the IoT Edge agent.
systemModules.edgeAgent.exitCode The exit code reported by the IoT Edge agent container if the container exits.
systemModules.edgeAgent.lastStartTimeUtc Time when IoT Edge agent was last started.
systemModules.edgeAgent.lastExitTimeUtc Time when IoT Edge agent last exited.
systemModules.edgeHub.runtimeStatus Status of IoT Edge hub: { running | stopped | failed | backoff | unhealthy }.
systemModules.edgeHub.statusDescription Text description of the status of IoT Edge hub, if unhealthy.
systemModules.edgeHub.exitCode Exit code reported by the IoT Edge hub container, if the container exits.
systemModules.edgeHub.lastStartTimeUtc Time when IoT Edge hub was last started.
systemModules.edgeHub.lastExitTimeUtc Time when IoT Edge hub was last exited.
systemModules.edgeHub.lastRestartTimeUtc Time when IoT Edge hub was last restarted.
systemModules.edgeHub.restartCount Number of times this module was restarted as part of the restart policy.
modules.{moduleId}.runtimeStatus Status of the module: { running | stopped | failed | backoff | unhealthy }.
modules.{moduleId}.statusDescription Text description of the status of the module, if unhealthy.
modules.{moduleId}.exitCode The exit code reported by the module container, if the container exits.
modules.{moduleId}.lastStartTimeUtc Time when the module was last started.
modules.{moduleId}.lastExitTimeUtc Time when the module was last exited.
modules.{moduleId}.lastRestartTimeUtc Time when the module was last restarted.
modules.{moduleId}.restartCount Number of times this module was restarted as part of the restart policy.
version Version of the image. Example: "version": { "version": "1.2.7", "build": "50979330", "commit": "d3ec971caa0af0fc39d2c1f91aef21e95bd0c03c" }.

EdgeHub desired properties

The module twin for the IoT Edge hub is called $edgeHub and coordinates the communications between the IoT Edge hub running on a device and IoT Hub. The desired properties are set when applying a deployment manifest on a specific device as part of a single-device or at-scale deployment.

Property Description Required in the deployment manifest
schemaVersion Either 1.0 or 1.1. Version 1.1 was introduced with IoT Edge version 1.0.10, and is recommended. Yes
routes.{routeName} A string representing an IoT Edge hub route. For more information, see Declare routes. The routes element can be present but empty.
storeAndForwardConfiguration.timeToLiveSecs The device time in seconds that IoT Edge hub keeps messages if disconnected from routing endpoints, whether IoT Hub or a local module. This time persists over any power offs or restarts. For more information, see Offline capabilities. Yes

EdgeHub reported properties

Property Description
lastDesiredVersion This integer refers to the last version of the desired properties processed by the IoT Edge hub.
lastDesiredStatus.code The status code referring to last desired properties seen by the IoT Edge hub. Allowed values: 200 Success, 400 Invalid configuration, 500 Failed
lastDesiredStatus.description Text description of the status.
clients All clients connected to edgeHub with the status and last connected time. Example: "clients": { "device2/SimulatedTemperatureSensor": { "status": "Connected", "lastConnectedTimeUtc": "2022-11-17T21:49:16.4781564Z" } }.
clients.{device or moduleId}.status The connectivity status of this device or module. Possible values {connected | disconnected}. Only module identities can be in disconnected state. Downstream devices connecting to IoT Edge hub appear only when connected.
clients.{device or moduleId}.lastConnectTime Last time the device or module connected.
clients.{device or moduleId}.lastDisconnectTime Last time the device or module disconnected.
schemaVersion Schema version of reported properties.
version Version of the image. Example: "version": { "version": "1.2.7", "build": "50979330", "commit": "d3ec971caa0af0fc39d2c1f91aef21e95bd0c03c" }.

Next steps

To learn how to use these properties to build out deployment manifests, see Understand how IoT Edge modules can be used, configured, and reused.