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Slack integration with JIRA breaking (Slack TLSv1.3 change?)


I am a consultant who manages companies' Atlassian apps.

Over the past 24h, two companies have reported that Jira's integration with Slack has suddenly broken. Restarting Jira lets a few Slack webhook calls through before it gets stuck again. Once stuck, no webhooks (even non-Slack) will go through.

To cut a long story short, this is due to a bug in Java 11's TLSv1.3 support. Jira is failing to close the TLS connection, which blocks the webhook thread queue:

This can be diagnosed by taking a thread dump (jstack -l <pid>) and looking for a BLOCKED thread named Web-Hook-Publisher-n, e.g.:

"Web-Hook-Publisher-2" #480 daemon prio=5 os_prio=0 cpu=2725.90ms elapsed=116091.79s tid=0x00007f6a6c794800 nid=0x2201 waiting for monitor entry [0x00007f68a43fa000]
java.lang.Thread.State: BLOCKED (on object monitor)
at org.apache.http.nio.reactor.ssl.SSLIOSession.close(
- waiting to lock <0x0000000724634b18> (a org.apache.http.nio.reactor.ssl.SSLIOSession)


There is a workaround in the JRASERVER reports. The bug is fixed in Java 12, and should be backported to the forthcoming Java 11.0.8.

Two instances hitting the same problem could be a coincidence, but it could be that Slack recently updated TLS somehow in their endpoint. They did remove TLSv1.0 and v1.1 support last month.

Has anyone else running Java 11 with Slack integration noticed this problem?



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