Monitoring is an example how state machine concepts can be used to monitor machine transitions and actions.

@Configuration
@EnableStateMachine
public static class Config extends StateMachineConfigurerAdapter<String, String> {

    @Override
    public void configure(StateMachineStateConfigurer<String, String> states)
            throws Exception {
        states
            .withStates()
                .initial("S1")
                .state("S2", null, (c) -> {System.out.println("hello");})
                .state("S3", (c) -> {System.out.println("hello");}, null);
    }

    @Override
    public void configure(StateMachineTransitionConfigurer<String, String> transitions)
            throws Exception {
        transitions
            .withExternal()
                .source("S1").target("S2").event("E1")
                .action((c) -> {System.out.println("hello");})
                .and()
            .withExternal()
                .source("S2").target("S3").event("E2");
    }
}

Let’s get into actual demo. Run the boot based sample application:

# java -jar spring-statemachine-samples-monitoring-2.0.1.RELEASE.jar

Execute some transitions.

Metrics can be viewed from Boot.

# curl http://localhost:8080/actuator/metrics/ssm.transition.duration

{
  "name":"ssm.transition.duration",
  "measurements":[
    {
      "statistic":"COUNT",
      "value":3.0
    },
    {
      "statistic":"TOTAL_TIME",
      "value":0.007
    },
    {
      "statistic":"MAX",
      "value":0.004
    }
  ],
  "availableTags":[
    {
      "tag":"transitionName",
      "values":[
        "INITIAL_S1",
        "EXTERNAL_S1_S2"
      ]
    }
  ]
}

# curl http://localhost:8080/actuator/metrics/ssm.transition.transit

{
  "name":"ssm.transition.transit",
  "measurements":[
    {
      "statistic":"COUNT",
      "value":3.0
    }
  ],
  "availableTags":[
    {
      "tag":"transitionName",
      "values":[
        "EXTERNAL_S1_S2",
        "INITIAL_S1"
      ]
    }
  ]
}

Tracing can be viewed from Boot.

# curl http://localhost:8080/actuator/statemachinetrace

[
  {
    "timestamp":"2018-02-11T06:44:12.723+0000",
    "info":{
      "duration":2,
      "machine":null,
      "transition":"EXTERNAL_S1_S2"
    }
  },
  {
    "timestamp":"2018-02-11T06:44:12.720+0000",
    "info":{
      "duration":0,
      "machine":null,
      "action":"demo.monitoring.StateMachineConfig$Config$$Lambda$576/1499688007@22b47b2f"
    }
  },
  {
    "timestamp":"2018-02-11T06:44:12.714+0000",
    "info":{
      "duration":1,
      "machine":null,
      "transition":"INITIAL_S1"
    }
  },
  {
    "timestamp":"2018-02-11T06:44:09.689+0000",
    "info":{
      "duration":4,
      "machine":null,
      "transition":"INITIAL_S1"
    }
  }
]