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Using actuator in Spring boot to analyze and monitor your application

Intro

Spring boot offers a wonderful module called the actuator. It is somewhat similar to the tools offered by Rails or other frameworks to get a better view of your application.

Basically when you enable it, you can browse to a url which by default is at /actuator (but can be configured), where you will find very interesting pieces of information about your Spring boot application.

For example, if you built a MVC webapp where you wrote a number of @Controller or @RestController classes, then going to /actuator/mappings will list your endpoints along with which controller method serve which endpoint etc.

But there is a whole lot more in actuator you will find useful.

In this article, I will show you how to use it in your application, and also how to only enable it in your development profile. I would assume that you don't want soething like this enabled in your production deployment. We will use Spring profiles for this.

Setup

I am assuming you have a working Spring boot application containing a structure somewhat like this:

src/main/resources/application.properties
src/main/java/...yourCode
build.gradle (if using gradle, otherwise Maven pom)

Adding Actuator to your application


Now all you have to do is add a dependency to spring-boot-starter kit for actuator. My gradle file had this in dependencies section:
runtime("org.springframework.boot:spring-boot-starter-actuator")
Runtime is usually appropriate for a tool like this, in terms of dependency scope. You don't want this to become part of your transitive dependency graph.

Now that's it, if you start your application, and browse to http://localhost:port/actuator you will see a number of available links.

If you don't see much, don't worry, it's because actuator does not by default enable many modules as of Spring 5.x (forget which version).

To make more module available here, jsut add something like this (or a variatoin of this) to your application.properties file

# We will use this only in dev mode, not a wise idea to do this in prod!# exposes spring-boot-actuator endpoints like /mappings 
management.endpoints.web.exposure.include=*
This is fully documented in spring actuator documentation, so I won't describe it, but briefly, tihs enables all available endpoints in actuator. I just do this in my development lifecycle.


Only enabling Actuator in development profile


This is optional and upto you of course, but I always do this to avoid exposing this in production. Spring has support for profiles. The steps below will make 'dev' the default profile, enable actuator in that profile, and not enable it in 'prod' profile.

Create two properties file in src/main/resources, so now it looks like this:

src/main/resources/
        application.properties
        application-dev.properties
        application-prod.properties

The contents can be like this, only showing actuator pieces:

application.properties:
spring.profiles.active=dev
# just whatever else you want by default in all profiles
application-dev.properties: 

     management.endpoints.web.exposure.include=*

application-prod.properties:
management.endpoints.web.exposure.exclude=*
       
That's it, now when you start without any switches you get 'dev' profile and actuator is fully enabled. When you start with -Dspring.profile.active=prod, you get no actuator endpoints.

Conclusion

Grab your favorite beverage at this point, and don't forget to - Enjoy!

Ref:

    1. https://docs.spring.io/spring-boot/docs/current/reference/html/production-ready-enabling.html




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