14. Metrics Emitter

14. Metrics Emitter
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Spring Boot Actuator provides dependency management and auto-configuration for Micrometer, an application metrics facade that supports numerous monitoring systems.

Spring Cloud Stream provides support for emitting any available micrometer-based metrics to a binding destination, allowing for periodic collection of metric data from stream applications without relying on polling individual endpoints.

Metrics Emitter is activated by defining the spring.cloud.stream.bindings.applicationMetrics.destination property, which specifies the name of the binding destination used by the current binder to publish metric messages.

For example:

spring.cloud.stream.bindings.applicationMetrics.destination=myMetricDestination

The preceding example instructs the binder to bind to myMetricDestination (that is, Rabbit exchange, Kafka topic, and others).

The following properties can be used for customizing the emission of metrics:

spring.cloud.stream.metrics.key

The name of the metric being emitted. Should be a unique value per application.

Default: ${spring.application.name:${vcap.application.name:${spring.config.name:application}}}

spring.cloud.stream.metrics.properties

Allows white listing application properties that are added to the metrics payload

Default: null.

spring.cloud.stream.metrics.meter-filter

Pattern to control the 'meters' one wants to capture. For example, specifying spring.integration.* captures metric information for meters whose name starts with spring.integration.

Default: all 'meters' are captured.

spring.cloud.stream.metrics.schedule-interval

Interval to control the rate of publishing metric data.

Default: 1 min

Consider the following:

java -jar time-source.jar \
    --spring.cloud.stream.bindings.applicationMetrics.destination=someMetrics \
    --spring.cloud.stream.metrics.properties=spring.application** \
    --spring.cloud.stream.metrics.meter-filter=spring.integration.*

The following example shows the payload of the data published to the binding destination as a result of the preceding command:

{
	"name": "application",
	"createdTime": "2018-03-23T14:48:12.700Z",
	"properties": {
	},
	"metrics": [
		{
			"id": {
				"name": "spring.integration.send",
				"tags": [
					{
						"key": "exception",
						"value": "none"
					},
					{
						"key": "name",
						"value": "input"
					},
					{
						"key": "result",
						"value": "success"
					},
					{
						"key": "type",
						"value": "channel"
					}
				],
				"type": "TIMER",
				"description": "Send processing time",
				"baseUnit": "milliseconds"
			},
			"timestamp": "2018-03-23T14:48:12.697Z",
			"sum": 130.340546,
			"count": 6,
			"mean": 21.72342433333333,
			"upper": 116.176299,
			"total": 130.340546
		}
	]
}

	Note
	Given that the format of the Metric message has slightly changed after migrating to Micrometer, the published message will also have a `STREAM_CLOUD_STREAM_VERSION` header set to `2.x` to help distinguish between Metric messages from the older versions of the Spring Cloud Stream.

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