Error Message :
Queue slots are not released after a Workflow has been canceled by the last Task inside a Workflow.
In order for this issue to occur when a Workflow (i.e. WF1) is submitted into a queue and one of the internal tasks within the workflow aborts, WF1 will remain in the queue in a status of BLOCKED. If a second Workflow (i.e. WF2) is submitted in the same queue that workflow will remain in a status of Waiting for Predecessor. Because the Job Queue is limited to a maximum of 1 Job execution at a time, the workflows are behaving as expected.
If the failed job within WF1 is executed again and it ends successfully, WF1 will continue and end in a status of ENDED_OK. The job queues slot is now released and WF2 should start. Instead, WF2 remains indefinitely in a status of Waiting for Predecessor.
OS: Windows Server 2012
OS Version: N/A
Root Cause: Queue-slots are not released after a workflow has been canceled by the last task inside the workflow.
Update to a fix version listed below or a newer version if available.
Fix Status: Released
Automation Engine 12.1.0 - Available
Automation Engine 12.0.3 - Available
Restart the job queue to release the waiting Workflow.