How to properly expose hikari metrics to prometheus

[andre.pinh...@gmail.com]

Hi all.

I'm trying to expose HikariCP metrics to Prometheus. I'm looking for the simplest and best approach to do that. I see here - https://github.com/brettwooldridge/HikariCP/wiki/Dropwizard-Metrics - that Hikari supports Dropwizard, configuring a MetricRegistry but does not explain how to do that. Also, in the source code of Hikari  - https://github.com/brettwooldridge/HikariCP/tree/dev/src/main/java/com/zaxxer/hikari/metrics/prometheus - I found some Java classes that seem to make all the work that it is needed to create a collector and the only thing that needs to be done is expose that collector. But, once again I don't understand how to do it.

So, I'm confused about how to expose the metrics.
 - What is the best approach?
 - How to configure the HikariConfig to do this?
 - how to expose the collector?

I'm using Kotlin, HikariCP 2.7.8 and using Ktor routing - https://ktor.io/servers/features/routing.html - to handling HTTP Requests.

Thanks in advance!

Best Regards,
André

[Brett Wooldridge]

I am not that familiar with Prometheus, most if not all of that code was contributed.  You can use the setMetricsTrackerFactory method on the config to set the registry with an instance of com.zaxxer.hikari.metrics.prometheus.PrometheusMetricsTrackerFactory.

-Brett

[andre.pinh...@gmail.com]

Hi Brett,

Thanks for your reply.

I will give a try to that.

Br,
André

[andre.pinh...@gmail.com]

Solved. In fact it is a really simple process. Above I leave my documentation of the process.
Thanks for your help Brett! ;)

Br,
André

---

HikariCP have support to expose metrics for Prometheus thanks to the contribution of the community. This pull request make really easy to expose metrics to prometheus.

There are three simple Steps:

1. Add prometheus-client dependency - add io.prometheus:simpleclient_servlet:0.6.0
2. Create a metric controller during the HikariCP configuration;
3. Expose the controller;

Create metric controller

HikariDataSource(HikariConfig().apply { driverClassName = "org.h2.Driver" jdbcUrl = "jdbc:h2:mem:test" maximumPoolSize = 5 isAutoCommit = true transactionIsolation = "TRANSACTION_REPEATABLE_READ" leakDetectionThreshold = 10000 poolName = "sat" metricsTrackerFactory = PrometheusMetricsTrackerFactory() validate() })

To create the controller you can use the setMetricsTrackerFactory method on the config to set the registry with an instance of com.zaxxer.hikari.metrics.prometheus.PrometheusMetricsTrackerFactory. Also it is recommended to give a name for the pool in case if you have different Hikari pools exposing metrics. This will collect the metrics to the the default registry.

Expose the controller

To expose the metrics for prometheus using ktor framework - and using routing feature - just need to create a new handler. This handle will respond with the metrics collected on the default registry. The endpoint "/metrics" the the default for prometheus.

package metrics import com.proj.common.io.http.ApiContentType import io.ktor.application.call import io.ktor.response.respondTextWriter import io.ktor.routing.Route import io.ktor.routing.accept import io.ktor.routing.get import io.prometheus.client.CollectorRegistry import io.prometheus.client.exporter.common.TextFormat fun Route.metricsHandler() { accept(ApiContentType.v1.test) { get("/metrics") { call.respondTextWriter{ TextFormat.write004(this, CollectorRegistry.defaultRegistry.metricFamilySamples()) } } } }