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dropwizard_metrics.md

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Required dependencies: io.ktor:%artifact_name%

The %plugin_name% plugin lets you configure the Metrics library to get useful information about the server and incoming requests.

The %plugin_name% plugin lets you configure the Metrics library to get useful information about the server and incoming requests.

Add dependencies {id="add_dependencies"}

To enable %plugin_name%, you need to include the following artifacts in the build script:

  • Add the %artifact_name% dependency:

  • Optionally, add a dependency required for a specific reporter. The example below shows how to add an artifact required to report metrics via JMX: You can replace dropwizard_version with the required version of the metrics-jmx artifact, for example, %dropwizard_version%.

Install %plugin_name% {id="install_plugin"}

Configure %plugin_name% {id="configure_plugin"}

%plugin_name% allows you to use any supported Metric reporter using the registry property. Let's take a look at how to configure the SLF4J and JMX reporters.

SLF4J reporter {id="slf4j"}

The SLF4J reporter allows you to periodically emit reports to any output supported by SLF4J. For example, to output the metrics every 10 seconds, you would:



{src="snippets/dropwizard-metrics/src/main/kotlin/com/example/MetricsApplication.kt" lines="12-18,25"}


You can find the full example here: dropwizard-metrics.


If you run the application and open http://0.0.0.0:8080, the output will look like this:


[DefaultDispatcher-worker-1] INFO  Application - Responding at http://0.0.0.0:8080
... type=COUNTER, name=ktor.calls.active, count=0
... type=METER, name=ktor.calls./(method:GET).200, count=6, m1_rate=1.2, m5_rate=1.2, m15_rate=1.2, mean_rate=0.98655785084844, rate_unit=events/second
... type=METER, name=ktor.calls./(method:GET).meter, count=6, m1_rate=1.2, m5_rate=1.2, m15_rate=1.2, mean_rate=0.9841134429134598, rate_unit=events/second
... type=METER, name=ktor.calls.exceptions, count=0, m1_rate=0.0, m5_rate=0.0, m15_rate=0.0, mean_rate=0.0, rate_unit=events/second
... type=METER, name=ktor.calls.status.200, count=6, m1_rate=1.2, m5_rate=1.2, m15_rate=1.2, mean_rate=0.9866015088545449, rate_unit=events/second
... type=TIMER, name=ktor.calls./(method:GET).timer, count=6, min=0.359683, max=14.213046, mean=2.691307542732234, stddev=5.099546889849414, p50=0.400967, p75=0.618972, p95=14.213046, p98=14.213046, p99=14.213046, p999=14.213046, m1_rate=1.2, m5_rate=1.2, m15_rate=1.2, mean_rate=0.9830677128229028, rate_unit=events/second, duration_unit=milliseconds
... type=TIMER, name=ktor.calls.duration, count=6, min=0.732149, max=33.735719, mean=6.238046092985701, stddev=12.169258340009847, p50=0.778864, p75=1.050454, p95=33.735719, p98=33.735719, p99=33.735719, p999=33.735719, m1_rate=0.2, m5_rate=0.2, m15_rate=0.2, mean_rate=0.6040311229887146, rate_unit=events/second, duration_unit=milliseconds


JMX reporter {id="jmx"}


The JMX reporter allows you to expose all the metrics to JMX, allowing you to view those metrics using jconsole.




{src="snippets/dropwizard-metrics/src/main/kotlin/com/example/MetricsApplication.kt" lines="12,19-23,25"}


You can find the full example here: dropwizard-metrics.


If you run the application and connect to its process using the JConsole, metrics will look like this:


Ktor Metrics: JMX{width="758"}


Exposed metrics {id="exposed-metrics"}


%plugin_name% exposes the following metrics:



Global metrics {id="global-metrics"}


Global metrics include the following Ktor-specific metrics:


    

  • ktor.calls.active:Count - The number of unfinished active requests.
    • 

  • ktor.calls.duration - Information about the duration of the calls.
    • 

  • ktor.calls.exceptions - Information about the number of exceptions.
    • 

  • ktor.calls.status.NNN - Information about the number of times that happened a specific HTTP status code NNN.
    • 



Note that a metric name starts with the ktor.calls prefix. You can customize it using the baseName property:


install(DropwizardMetrics) {
    baseName = "my.prefix"
}


Metrics per endpoint {id="endpoint-metrics"}


    

  • "/uri(method:VERB).NNN" - Information about the number of times that happened a specific HTTP status code NNN, for this path and verb.
    • 

  • "/uri(method:VERB).meter" - Information about the number of calls for this path and verb.
    • 

  • "/uri(method:VERB).timer" - Information about the duration for this endpoint.
    • 



JVM metrics {id="jvm-metrics"}


In addition to HTTP metrics, Ktor exposes a set of metrics for monitoring the JVM. You can disable these metrics using the registerJvmMetricSets property:




{src="snippets/dropwizard-metrics/src/main/kotlin/com/example/MetricsApplication.kt" lines="12,24-25"}


You can find the full example here: dropwizard-metrics.