Spring Boot: Prometheus actuator endpoint

In this post I show how you can add support for Prometheus in Spring Boot applications.

Step 1 of 2: Add the Prometheus Spring Boot Starter

You can get Prometheus support in Spring Boot applications via a so-called “starter”. Here is how to get that…

It’s a one liner in Gradle:

compile 'com.moelholm:prometheus-spring-boot-starter:1.0.1'

And a five liner in Maven:

<dependency>
  <groupId>com.moelholm</groupId>
  <artifactId>prometheus-spring-boot-starter</artifactId>
  <version>1.0.1</version>
</dependency>

That’s it. Ready for testing it?

Step 2 of 2: Test it

Now you have a new Spring Boot Actuator endpoint. If you haven’t changed the management port and default application port – then you can find it here:

http://localhost:8080/prometheus

That will give you output like this:

# HELP httpsessions_max httpsessions_max
# TYPE httpsessions_max gauge
httpsessions_max -1.0
# HELP httpsessions_active httpsessions_active
# TYPE httpsessions_active gauge
httpsessions_active 0.0
# HELP mem mem
# TYPE mem gauge
mem 368223.0
# HELP mem_free mem_free
# TYPE mem_free gauge
mem_free 226605.0
... ( and so on and so forth forever ) ...

I have created a working example on GitHub – consult that to see the starter used and validated from an integration test.

Optional configuration

The Prometheus endpoint can be configured via 2 properties:

  • endpoints.prometheus.path
  • endpoints.prometheus.sensitive

The first one defaults to /prometheus. The second one defaults to false. Feel free to change any one of them by setting the properties in your Spring Boot application.properties file (or YAML if you are into that stuff).

About the Spring Boot Starter

I recently had to add Prometheus support to some of our Spring Boot applications at my work.

I searched (a bit) and did find another nice starter by Thomas Darimont [1]. The problem with this starter, for us, was that it:

  • Wasn’t in the Maven Central
  • Didn’t add the Prometheus endpoint as a real Spring Boot Actuator endpoint

I also found another starter by Oleg Vyukov [2]. But I found the implementation a bit complicated – at least compared with other material on how to manually activate a Prometheus endpoint. That made me a bit nervous…

So I figured: why not…create another starter myself :). That is the one you see referenced in the above example. You can find the source code for it on GitHub:

https://github.com/nickymoelholm/prometheus-spring-boot-starter

References

[1] Thomas Darimont’s starter:
https://github.com/thomasdarimont/prometheus-spring-boot-starter

[2] Oleg Vyukov’s starter:
https://github.com/akaGelo/spring-boot-starter-prometheus

Tagged with: ,
Posted in Spring

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: