Issue fails to create with indexing errors

Problem

Issue creation fails for no obvious reason and JEMH processing details do not suggest why. In JEMH logs you see something similar to this:

2016-09-16 13:20:15,599 atlassian-scheduler-quartz1.clustered_Worker-2 DEBUG [jira.emh.engine.IssueCreationHelper] Create resulted in 0 errors
2016-09-16 13:20:15,687 atlassian-scheduler-quartz1.clustered_Worker-2 INFO [jira.emh.engine.IssueCreationHelper] issue not created!!!
2016-09-16 13:20:15,687 atlassian-scheduler-quartz1.clustered_Worker-2 INFO [jira.emh.engine.IssueCreationHelper] Error creating issue: Indexing completed with 4 errors

Solution

A possible cause of this is that the UNIX open file limit has been reached by the JIRA application.  See here for more information on this, including workarounds: https://confluence.atlassian.com/jirakb/loss-of-functionality-due-to-too-many-open-files-errors-156862102.htm