Nucleus telemetry emitter

The nucleus telemetry emitter component (aws.greengrass.telemetry.NucleusEmitter) gathers system health telemetry data and publishes it continually to a local topic and an AWS IoT Core MQTT topic. This component enables you to gather real-time system telemetry on your Greengrass core devices. For information about the Greengrass telemetry agent that publishes system telemetry data to Amazon EventBridge, see Gather system health telemetry data from AWS IoT Greengrass core devices.

By default, the nucleus telemetry emitter component publishes telemetry data every 60 seconds to the following local publish/subscribe topic.

$local/greengrass/telemetry

The nucleus telemetry emitter component doesn't publish to an AWS IoT Core MQTT topic by default. You can configure this component to publish to an AWS IoT Core MQTT topic when you deploy it. The use of an MQTT topic to publish data to the AWS Cloud is subject to AWS IoT Core pricing.

AWS IoT Greengrass provides several community components to help you analyze and visualize telemetry data locally on your core device using InfluxDB and Grafana. These components use telemetry data from the nucleus emitter component. For more information, see the README for the InfluxDB publisher component.

Versions

This component has the following versions:

Type

This component is a plugin component (aws.greengrass.plugin). The Greengrass nucleus runs this component in the same Java Virtual Machine (JVM) as the nucleus. The nucleus restarts when you change this component's version on the core device.

This component uses the same log file as the Greengrass nucleus. For more information, see Monitor AWS IoT Greengrass logs.

For more information, see Component types.

Operating system

Dependencies

When you deploy a component, AWS IoT Greengrass also deploys compatible versions of its dependencies. This means that you must meet the requirements for the component and all of its dependencies to successfully deploy the component. This section lists the dependencies for the released versions of this component and the semantic version constraints that define the component versions for each dependency. You can also view the dependencies for each version of the component in the AWS IoT Greengrass console. On the component details page, look for the Dependencies list.

For more information about component dependencies, see the component recipe reference.

Configuration

This component provides the following configuration parameters that you can customize when you deploy the component.

{
  "pubSubPublish": "true",
  "mqttTopic": "greengrass/myTelemetry",
  "telemetryPublishIntervalMs": 5000
}

Output data

This component publishes telemetry metrics as a JSON array on the following topic.

Local topic: $local/greengrass/telemetry

You can optionally choose to also publish telemetry metrics to an AWS IoT Core MQTT topic. For more information about topics, see MQTT topics in the AWS IoT Core Developer Guide.

[
  {
    "A": "Average",
    "N": "CpuUsage",
    "NS": "SystemMetrics",
    "TS": 1627597331445,
    "U": "Percent",
    "V": 26.21981271562346
  },
  {
    "A": "Count",
    "N": "TotalNumberOfFDs",
    "NS": "SystemMetrics",
    "TS": 1627597331445,
    "U": "Count",
    "V": 7316
  },
  {
    "A": "Count",
    "N": "SystemMemUsage",
    "NS": "SystemMetrics",
    "TS": 1627597331445,
    "U": "Megabytes",
    "V": 10098
  },
  {
    "A": "Count",
    "N": "NumberOfComponentsStarting",
    "NS": "GreengrassComponents",
    "TS": 1627597331446,
    "U": "Count",
    "V": 0
  },
  {
    "A": "Count",
    "N": "NumberOfComponentsInstalled",
    "NS": "GreengrassComponents",
    "TS": 1627597331446,
    "U": "Count",
    "V": 0
  },
  {
    "A": "Count",
    "N": "NumberOfComponentsStateless",
    "NS": "GreengrassComponents",
    "TS": 1627597331446,
    "U": "Count",
    "V": 0
  },
  {
    "A": "Count",
    "N": "NumberOfComponentsStopping",
    "NS": "GreengrassComponents",
    "TS": 1627597331446,
    "U": "Count",
    "V": 0
  },
  {
    "A": "Count",
    "N": "NumberOfComponentsBroken",
    "NS": "GreengrassComponents",
    "TS": 1627597331446,
    "U": "Count",
    "V": 0
  },
  {
    "A": "Count",
    "N": "NumberOfComponentsRunning",
    "NS": "GreengrassComponents",
    "TS": 1627597331446,
    "U": "Count",
    "V": 7
  },
  {
    "A": "Count",
    "N": "NumberOfComponentsErrored",
    "NS": "GreengrassComponents",
    "TS": 1627597331446,
    "U": "Count",
    "V": 0
  },
  {
    "A": "Count",
    "N": "NumberOfComponentsNew",
    "NS": "GreengrassComponents",
    "TS": 1627597331446,
    "U": "Count",
    "V": 0
  },
  {
    "A": "Count",
    "N": "NumberOfComponentsFinished",
    "NS": "GreengrassComponents",
    "TS": 1627597331446,
    "U": "Count",
    "V": 2
  }
]

The nucleus emitter publishes the following metrics:

Usage

To use system health telemetry data, you can create custom components that subscribe to the topics to which the nucleus emitter publishes the telemetry data, and react to that data as needed. Because the nucleus emitter component provides the option to publish telemetry data to a local topic, you can subscribe to that topic, and use the published data to act locally on your core device. The core device can then react to telemetry data even when it has limited connectivity to the cloud.

For example, you can configure a component that listens on the $local/greengrass/telemetry topic for telemetry data and send the data to the stream manager component to stream your data to the AWS Cloud. For more information about creating such a component, see Publish/subscribe local messages and Create custom components that use stream manager.

Local log file

This component uses the same log file as the Greengrass nucleus component.

Changelog

The following table describes the changes in each version of the component.