flowable/flowable-engine · error · FlowableException

Empty timer job can not be scheduled

Error message

Empty timer job can not be scheduled

What it means

DefaultJobManager.moveTimerJobToExecutableJob promotes a TimerJobEntity to a runnable JobEntity when its due date arrives. A null timer job has nothing to schedule, so the method throws this FlowableException as a fail-fast precondition before creating the executable job.

Solutions

1. Check timerJob != null before calling moveTimerJobToExecutableJob and skip/log instead
2. Fix the upstream query/acquisition code that produced a null timer job
3. Wrap the call and treat FlowableException as an indicator of a lifecycle race, then re-fetch

Example fix

// before
jobManager.moveTimerJobToExecutableJob(timerJob); // may be null
// after
if (timerJob != null) {
    jobManager.moveTimerJobToExecutableJob(timerJob);
}

if (timerJob == null) { log.warn("No timer job to move to executable"); return; }

boolean canSchedule(TimerJobEntity t) { return t != null && t.getId() != null; }

try { jobManager.moveTimerJobToExecutableJob(timerJob); } catch (FlowableException e) { log.warn("Timer job became null/absent before move: {}", e.getMessage()); }

When it happens

Trigger: Passing null to JobManager.moveTimerJobToExecutableJob(timerJob), typically when a timer lookup/acquisition returned null and the result was forwarded without a null check.

Common situations: Custom async executor or timer acquisition logic that iterates results of a timer-job query and doesn't skip nulls; race conditions where the timer job was deleted between fetch and move.

Related errors

• Empty external worker job can not be scheduled
• Null job provided
• activity tenant id is null
• activityId is null
• after time is null

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/74ad1549eb4643e4. Report an issue: GitHub.

Appendix: source

Thrown at modules/flowable-job-service/src/main/java/org/flowable/job/service/impl/asyncexecutor/DefaultJobManager.java:129

        String category = jobEntity.getCategory();
        if (StringUtils.isEmpty(category)) {
            // If the job has no category then we should not hint it, another node needs to run it
            return false;
        }

        // Finally, the job should be hinted if the enabled job categories contain the job category
        return enabledJobCategories.contains(category);
    }

    @Override
    public void scheduleTimerJob(TimerJobEntity timerJob) {
        jobServiceConfiguration.getTimerJobScheduler().scheduleTimerJob(timerJob);
    }

    @Override
    public JobEntity moveTimerJobToExecutableJob(TimerJobEntity timerJob) {
        if (timerJob == null) {
            throw new FlowableException("Empty timer job can not be scheduled");
        }

        JobEntity executableJob = createExecutableJobFromOtherJob(timerJob);
        boolean insertSuccessful = jobServiceConfiguration.getJobEntityManager().insertJobEntity(executableJob);
        if (insertSuccessful) {
            jobServiceConfiguration.getTimerJobEntityManager().delete(timerJob);
            triggerExecutorIfNeeded(executableJob);
            return executableJob;
        }
        return null;
    }

    @Override
    public void bulkMoveTimerJobsToExecutableJobs(List<TimerJobEntity> timerJobEntities) {

        if (timerJobEntities == null || timerJobEntities.isEmpty()) {
            throw new FlowableException("Empty timer jobs collection can not be scheduled");
        }

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