Working on busy Jira instance could result in a deadlock condition for the SdOffThreadEventJobRunner while scanning PSMQ queues.

Issue Summary

On busy large Jira instance (Jira 8.3.0+ with JSD 4.3.0 or higher), the SdOffThreadEventJobRunner threads might run into an active deadlock situation constantly trying to poll the PSMQ table.

Summary of the problem:

• As of JSD 4.3.0 the SdOffThreadEventJobRunner thread pool is limited to 5 threads by default.
• Upon an issue update, If none of the 5 threads have issue context to process the first item in the queue, none of them will be able to process that event and they will continue polling the queue forever.
• This problem could be triggered on a large very active instance, mainly if a certain issue is getting too frequent updates in a short time.
• This could result is a huge database pressure and could cause a performance issue for Jira is the database can't keep up.
• Such a deadlock will be resolved eventually, but some issues might end up with a corrupted SLA.

Steps to Reproduce

• NA - was not able to reproduce locally.
• The issue was observed on large very active client instances

Expected Results

• The SdOffThreadEventJobRunner thread should not be polling messages over and over in a deadlock situation.
• The amount of traffic to the database should be normal.

Actual Results

The logs (with Debug enabled on com.querydsl) show a huge amount of queries (40k+) hitting the database over and over:

$ grep "AO_319474_QUEUE" atlassian-jira.log.*|grep "update" |grep 'set "CLAIMANT" =' |cut -d" " -f6,9 |sort |uniq -c
      5  
   9110 1005x1479882x8 /servicedesk/customer/portal/9/create/94
  18379 1005x1480033x3 /rest/api/2/issue/SAT-30983/comment
  12949 1005x1480061x6 /secure/CommentAssignIssue.jspa

$ grep -n "AO_319474_MESSAGE" atlassian-jira.log* |grep "count(" |cut -d" " -f6,9 |sort |uniq -c
      3  
   9407 1005x1479882x8 /servicedesk/customer/portal/9/create/94
  18631 1005x1480033x3 /rest/api/2/issue/SAT-30983/comment
  13325 1005x1480061x6 /secure/CommentAssignIssue.jspa
  

Also checking the AO_319474_MESSAGE table shows that there is at least 1 message that is being claimed more than once:

Note

• Increasing the number of SdOffThreadEventJobRunner threads from 5 to 12 didn't actually help mitigate the issue.
• Increasing the threads much further to a much bigger number could trigger another issue similar to what was fixed by OffThreadEventJobRunner uses an unbounded ThreadPoolExecutor that can exhaust the DBCP - JSDSERVER-5732
• Related KB - Deadlocking in Jira Service Desk when frequently updating the same issue

Workaround

There is no known effective workaround for this issue currently.