Confluence startup fails being terminated by Synchrony

Summary

Confluence makes Synchrony start as a different process at its startup, then the Synchrony has an implementation to stop the existing Synchrony process and newly start.
And the process id of "existing Synchrony Process" is obtained from synchrony.pid file. Therefore, if the Confluence pid or its child thread id matched with synchrony.pid, Synchrony terminates the Confluence process.

For example, suppose such cases.

• 8th May ：Started with Confluence process id = 100, Synchrony process id = 101　
• 9th May ：Started with Confluence process id = 101, Synchrony process id = 102
  Then on the 9th May, the Synchrony startup terminates process id=101 i.e. Confluence process.

Or

• 8th May ：Started with Confluence process id = 100, thread id =101,102,103,104,105 and Synchrony process id = 110　
• 9th May ：Started with Confluence process id = 106, thread id =107,108,109,110,111 and Synchrony process id = 120
  Then on the 9th May, the Synchrony startup terminates process id=110 i.e. Confluence thread. And killing a thread means killing the parent process. Process id 106 dies at the same time.

Environment

• Confirmed at Linux environment at least. However this may occurs on Windows as well.

Steps to Reproduce

Following is a way to simulate this issue.

1. Start Confluence and Synchrony
2. Note the Confluence process id by the following command

   ps -ef | grep confluence
   

3. Change the <confluence-install-directory>/temp/synchrony.pid to the one obtained at step 2.
4. Go to Setting->Collaborative Editting->Restart Synchrony

Expected Results

Synchrony starts and Confluence/Synchrony works properly.

Actual Results

Confluence terminates.

Please note this screenshot is just a simulation that uses "Restart Synchrony". Problem is same thing occurs when on the Confluence startup.

Notes

• It is considered that this issue is more likely to occur if
  • Confluence is started at the boot of computer every time.
  • Confluence allows a lot of the threads.

Workaround

Add the following code at the beginning of the start-confluence.sh.

rm -f <confluence-install-directory>/temp/synchrony.pid