How to query scheduled processes (timer events)?

Question

If I schedule the start time of processes by using timer start events, how can I query which processes will start and when?

Also, I have the same question for the catching timer intermediate event. Does the camunda engine provides an API (Java or REST) to query which timers are running and when they are expected to expire?

Answer 1

You can retrieve the next scheduled execution times of your processes which use timer events through the Java and REST API like the following:

Example Java API:

import org.camunda.bpm.ProcessEngineService;
import org.camunda.bpm.container.RuntimeContainerDelegate;
import org.camunda.bpm.engine.ManagementService;
import org.camunda.bpm.engine.ProcessEngine;
import org.camunda.bpm.engine.RepositoryService;
import org.camunda.bpm.engine.management.JobDefinition;
import org.camunda.bpm.engine.repository.ProcessDefinition;
import org.camunda.bpm.engine.runtime.Job;

import java.util.HashMap;
import java.util.List;

public class StackOverflow {

  public HashMap<ProcessDefinition, List<Job>> queryNextScheduledExecutionOfTimers() {
    ProcessEngineService processEngineService = 
    RuntimeContainerDelegate.INSTANCE.get().getProcessEngineService();
    ProcessEngine defaultProcessEngine = processEngineService.getDefaultProcessEngine();

    // optional step - get all active process definitions
    RepositoryService repositoryService = defaultProcessEngine.getRepositoryService();
    List<ProcessDefinition> processDefinitions =
        repositoryService.createProcessDefinitionQuery().active().list();

    ManagementService managementService = defaultProcessEngine.getManagementService();

    HashMap<ProcessDefinition,List<Job>> timerJobsByProcessDefinition = new HashMap<ProcessDefinition, List<Job>>();
    for (ProcessDefinition processDefinition : processDefinitions) {
      List<JobDefinition> jobDefinitions =
          managementService.createJobDefinitionQuery()
              .active()
              .processDefinitionId(processDefinition.getId())
              .list();

      for (JobDefinition jobDefinition : jobDefinitions) {
        // if you want to lookup the activity to highlight it inside the process diagram for example
        String activityId = jobDefinition.getActivityId();
        // if you want to display the configured expression / date / cron expression when the timer should fire
        String jobConfiguration = jobDefinition.getJobConfiguration();
        // if you want to distinguish between timer start event / catching timer intermediate event / boundary timer event
        String timerType = jobDefinition.getJobType();

        List<Job> jobs = managementService.createJobQuery()
            .active()
            .timers()
            .jobDefinitionId(jobDefinition.getId())
            .orderByJobDuedate()
            .list();

        timerJobsByProcessDefinition.put(processDefinition, jobs);
      }
    }

    return timerJobsByProcessDefinition;
  }
}

Example REST API:

use http://localhost:8080/engine-rest/process-definition/ to retrieve the process definitions

for each process definition query the job definitions via http://localhost:8080/engine-rest/job-definition?active=true&processDefinitionId=${YOUR_PROCESS_DEFINITION_ID}

for each process definition query the jobs via http://localhost:8080/engine-rest/job?active=true&timers=true&processDefinitionId=${YOUR_PROCESS_DEFINITION_ID}

then you must correlate the resulting jobs with the job configurations using the jobConfigurationId.