livelessons-operations-actuator

Lesson 3: Creating Operations-Friendly Microservices (Logging)

Introduction

Provides an introduction to Spring Boot Actuator.

Building and running the sample

Use the following commands to build run the application:

$ mvn clean package
$ java -jar target/livelessons-operations-actuator-1.0.0-SNAPSHOT.jar

HTTP Endpoints

The following HTTP endpoints can be inspected in a running application:

• /autoconfig

• /beans

• /configprops

• /dump

• /env

• /health

• /info

• /metrics

• /mappings

• /trace

JMX

To view the same information using JMX you can use jconsole:

$ jconsole

Select demo.OperationsActuatorApplication from the “local applications” section (use insecure connection if asked) then click on the MBeans tab. You can the endpoints under org.springframework.boot/Endpoint pick an endpoint then click the getData button under operations.

SSH

You can ssh into the running application using the following command:

$ ssh -p 2000 livelessons@localhost

The password is livelessons (see application.properties).

Type help to get a list of commands. Endpoints can be executed using endpoint invoke <name> (for example endpoint invoke info). Several endpoints are also surfaced directly (for example metrics). The dashboard command is also quite fun.

JMX over Jolokia

Jolokia allows you to expose JMX beans over HTTP. Adding the library is all you need to do to configure it with Spring Boot. It can be useful if you have existing MBeans (or MBeans exposed by libraries that you use).

Here is an example call that will return HeapMemoryUsage information from the Memory MBean in java/lang:

$ curl http://localhost:8080/jolokia/read/java.lang:type=Memory/HeapMemoryUsage

Using the Git Commit ID

This sample includes the git-commit-id-plugin`Maven Plugin which will write a `git.properties file whenever the project is build. This information is automatically exposed on the /info endpoint.

The commit SHA is very useful when running applications in production as it allows you to know exactly which commit was used to build the running app. You also use this to get back to the POM.xml or build.gradle and know exactly which library versions were used when the app was built.