Bitbucket Server cannot create to new connections due to "No buffer space available (maximum connections reached?)"

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Platform notice: Server and Data Center only. This article only applies to Atlassian products on the server and data center platforms.


Bitbucket Server cannot open new sockets.

The following appears in the atlassian-bitbucket.log:

ERROR [Caesium-1-4]  c.a.scheduler.core.JobLauncher Scheduled job with ID '<job id>' failed
java.lang.IllegalStateException: org.apache.http.nio.reactor.IOReactorException: Failure opening selector
Caused by: org.apache.http.nio.reactor.IOReactorException: Failure opening selector
Caused by: Unable to establish loopback connection
Caused by: No buffer space available (maximum connections reached?): bind


Bitbucket Server can't create any new sockets when it's trying to talk to other services (e.g. database or external user directory). This could be caused by another application on the same server as Bitbucket Server and exhausting the available sockets.

The following command can be used to report the sockets in use:

netstat -n


There are various options to resolve this:

  • identify what's using the sockets and reduce the numbers
  • increase the number of available sockets

Last modified on Jun 20, 2018

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