Qlik Sense - Scheduler service error TaskExecutionSession already exists

Occasionally the Qlik Sense Scheduler service stops and shows errors related to:

TaskExecutionSession already exists

DescriptionCommand=Start task;Result=30;ResultText=Error: Failed

MessageTaskExecutionSession already exists for App <App.Name>
 

This issue happens when an app reload session is already in progress and gets interrupted then tries to resume.

1. Either server restart 

2. Server resource consumption and non responsiveness
 

The scheduler logs will refer to a specific app / task name

To resolve, see if you can change the reload time of these apps tasks one at a time to confirm it is causing the issue.

Also you can:

• Wait until the task that is reloading the app has completed.
• Stop the task that is reloading the app.
• Restart the QSS.

More info at:

https://help.qlik.com/en-US/sense/June2019/Subsystems/Troubleshooting-Qlik-Sense-using-logs/Content/Sense_ServerLogTroubleshoot/ServerLogTroubleshoot-Scheduler-Start-Task.htm

A task execution session represents a single execution of a task. The QRS ExecutionSession entity is created when the task is triggered (and no session already exists) and is deleted when the task either succeeds or fails. If the task is configured so that it is retried upon failure then the execution session may involve several retries and consequently result in several ExecutionResult entities.

See also:

https://support.qlik.com/articles/000052991