Enable Metrics

Metrics are disable by default. The gathering of metrics as well as exposing them via HTTP for analysis needs to be enabled first.

Enable HTTP and WebService calls enable the Servlet Filter

Comment in the following block in the openmeetings/WEB-INF/web.xml

<!-- Start Prometheus Filter HTTP Servlet metrics
	<filter>
		<filter-name>prometheusFilter</filter-name>
		<filter-class>io.prometheus.client.filter.MetricsFilter</filter-class>
		<init-param>
			<param-name>metric-name</param-name>
			<param-value>webapp_metrics_filter</param-value>
		</init-param>
		<init-param>
			<param-name>help</param-name>
			<param-value>This is the help for your metrics filter</param-value>
		</init-param>
		<init-param>
			<param-name>buckets</param-name>
			<param-value>0.005,0.01,0.025,0.05,0.075,0.1,0.25,0.5,0.75,1,2.5,5,7.5,10</param-value>
		</init-param>
		<init-param>
			<param-name>path-components</param-name>
			<param-value>0</param-value>
		</init-param>
	</filter>

	<filter-mapping>
		<filter-name>prometheusFilter</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>
	End Prometheus -->

Enable Exposing the metrics and enable Tomcat generic metrics

To enable the export of the metrics as well as some generic Tomcat export (for example around active threads) you need to comment in the following block in openmeetings/WEB-INF/In order to enable the metrics to be published as endpoint comment in the servlet in the web.xml

<!-- Start Prometheus export metrics HTTP
	<servlet>
  		<servlet-name>metrics</servlet-name>
  		<servlet-class>io.prometheus.client.exporter.MetricsServlet<class>org.apache.openmeetings.web.util.logging.OpenMeetingsMetricsServlet</servlet-class>
	</servlet>
	<servlet-mapping>
  		<servlet-name>metrics</servlet-name>
  		<url-pattern>/services/metrics/</url-pattern>
	</servlet-mapping>
	End Prometheus -->

This will expose the metrics atSee: http://$HOST:$PORT/openmeetings/services/metrics/ (be aware of the trailing "/" !)

Enable metrics for streaming and other application relevant metrics

In order to get insights on the application specific logic and streaming relevant components you need to additionally enable certain annotations by commenting in openmeetingsopenmeetings-web/src/main/webapp/WEB-INF/classes/web.xml#L110applicationContext.xml

<!-- Start annotation Prometheus metrics
	<aop:aspectj-autoproxy/>
	End annotation -->

View your metrics in Prometheus

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global:
  scrape_interval:     15s # By default, scrape targets every 15 seconds.
  evaluation_interval: 15s # Evaluate rules every 15 seconds.

  # Attach these extra labels to all timeseries collected by this Prometheus instance.
  external_labels:
    monitor: 'scalyr-blog'

rule_files:
  - 'prometheus.rules.yml'

scrape_configs:
  - job_name: 'prometheus'

    # Override the global default and scrape targets from this job every 5 seconds.
    scrape_interval: 5s

    static_configs:
      - targets: ['localhost:9090']

  - job_name:       'openmeetings-local'

    # Override the global default and scrape targets from this job every 5 seconds.
    scrape_interval: 5s

    metrics_path:  'openmeetings/services/metrics/'

    static_configs:
      - targets: ['192.168.1.66:5080']
        labels:
          group: 'production'

Change 192Change 192.168.1.66:5080 to your local running OpenMeetings instance. Below graphs and queries are done using this docker container.

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Majority of the metrics collected (as specially the below detailed ones) at are of the Prometheus type "histogram" https://prometheus.io/docs/practices/histograms/

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Initially you may find it's not quite trivial to calculate the duration for individual calls. But it makes sense once you review below. What we are interested is "rate pre per min" and similar statistics. Not an individual call, but rate/average over a certain period of time.

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Application metrics based on manual metric

Unfortunate not all places in the code are spring beans. Also sometimes we have inner classes or similar issues.

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