Metrics with Dropwizard metrics

预计阅读时间： 4 分钟

The Metrics feature allows you to configure the Metrics to get useful information about the server and incoming requests.

本特性在构件 io.ktor:ktor-metrics:$ktor_version 中的 io.ktor.metrics.DropwizardMetrics 类中定义。

dependencies {
    implementation "io.ktor:ktor-metrics:$ktor_version"
}

dependencies {
    implementation("io.ktor:ktor-metrics:$ktor_version")
}

<project>
    ...
    <dependencies>
        <dependency>
            <groupId>io.ktor</groupId>
            <artifactId>ktor-metrics</artifactId>
            <version>${ktor.version}</version>
            <scope>compile</scope>
        </dependency>
    </dependencies>
</project>

Installing

The Metrics feature exposes a registry property, that can be used to build and start metric reporters.

JMX Reporter

The JMX Reporter allows you to expose all the metrics to JMX, allowing you to view those metrics with jconsole or jvisualvm with the MBeans plugin.

install(DropwizardMetrics) {
    JmxReporter.forRegistry(registry)
        .convertRatesTo(TimeUnit.SECONDS)
        .convertDurationsTo(TimeUnit.MILLISECONDS)
        .build()
        .start()
}

Ktor Metrics: JMX

SLF4J Reporter

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:

install(DropwizardMetrics) {
    Slf4jReporter.forRegistry(registry)
        .outputTo(log)
        .convertRatesTo(TimeUnit.SECONDS)
        .convertDurationsTo(TimeUnit.MILLISECONDS)
        .build()
        .start(10, TimeUnit.SECONDS)
}

Ktor Metrics: SLF4J

Other reporters

You can use any of the available Metric reporters.

Exposed reports

This feature exposes many JVM properties relating to memory usage and thread behavior.

Global:

Specifically to Ktor, it exposes:

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

Per endpoint:

"/uri(method:VERB).NNN" - Information about the number of times that happened a specific HTTP Status Code NNN, for this path, for this verb
"/uri(method:VERB).meter" - Information about the number of calls for this path, for this verb
"/uri(method:VERB).timer" - Information about the durations for this endpoint

Information per report

Durations

"/uri(method:VERB).timer" and ktor.calls.duration are durations and expose:

50thPercentile
75thPercentile
95thPercentile
98thPercentile
99thPercentile
999thPercentile
Count
DurationUnit
OneMinuteRate
FifteenMinuteRate
FiveMinuteRate
Max
Mean
MeanRate
Min
RateUnit
StdDev

Counts

The other properties are exposed as counts:

Count
FifteenMinuteRate
FiveMinuteRate
OneMinuteRate
MeanRate
RateUnit