Summary

Deleting a comment from a page with many watchers, or many space watchers (100+) is slow and can take more than 60 seconds.

Environment

• Confluence 6.4.3

Steps to Reproduce

1. Set up Confluence 6.4.3 (or latest)
2. Use the Atlassian Populator to create 1000 users, 100 at a time.
3. Go to Confluence and create a Space and watch that Space.
4. Go to the database, and get the spaceid of the Space you're working with, e.g.

   select spaceid from spaces where spacekey = 'BUG';
   

   Let's say it's 12345

5. Update the notifications table so all the users watch the sample Space

   insert into notifications (notificationid, spaceid, username, creator, creationdate, lastmodifier, lastmoddate, digest, network) (select floor(random()*1000000), 12345, user_key, user_key, current_timestamp, user_key, current_timestamp, false, false from user_mapping);
   

   You may have to run this several times before you get 1000 unique random numbers. (If you know a better way to grab an id, please share.)

6. Go to General Configuration > Cache Management, scroll down and click Flush all
7. Create a page, add a comment (this is pretty quick)
8. Delete the comment (this is pretty slow)

Expected Results

The comment is deleted quickly

Actual Results

The below exception is thrown in the atlassian-confluence.log file:

2017-11-02 18:28:01,560 WARN [http-nio-8090-exec-6] [confluence.util.profiling.DurationThresholdWarningTimingHelperFactory] logMessage Execution time for publishing event com.atlassian.confluence.event.events.content.comment.CommentRemoveEvent[source=com.atlassian.confluence.pages.DefaultCommentManager@149e17af] took 33451 ms (warning threshold is 5000 ms)
 -- url: /pages/removecomment.action | page: 2228571 | traceId: 71638ddfefef7f55 | userName: admin | referer: http://confluence.mycompany.com:8090/display/BUG/CONFSERVER-54140 | action: removecomment

and catalina.out will also have similar warnings like this

25-Oct-2017 00:27:55.595 WARNING [ContainerBackgroundProcessor[StandardEngine[Standalone]]] org.apache.catalina.valves.StuckThreadDetectionValve.notifyStuckThreadDetected Thread "http-nio-8150-exec-50" (id=263) has been active for 61,319 milliseconds (since 10/25/17 12:26 AM) to serve the same request for https://confluence.mycompany.com/pages/removecomment.action?commentId=133300287&pageId=120587236&atl_token=71472d2d5b654afc06a736af45a98f718cd3aa50&confirm=yes and may be stuck (configured threshold for this StuckThreadDetectionValve is 60 seconds). There is/are 1 thread(s) in total that are monitored by this Valve and may be stuck.
 java.lang.Throwable

Notes

The slow code is going through a synchronous call to send the notifications. Thread dumps show most of the time is spent in

at com.atlassian.confluence.mail.notification.listeners.CommentNotificationsListener.handleCommentRemove(CommentNotificationsListener.java:71)

Workaround

There is no workaround.