During startup of Bitbucket Server there exists a small window where incoming Git hosting operations via SSH can become deadlocked. Although only SSH connections can cause the deadlock, the resulting exhaustion of hosting tickets may result in other requests, for example those via HTTP, becoming blocked.

Symptoms will include:

• Git hosting operations (e.g. clone, pull, push) may become blocked and fail after (by default) 300 seconds
• Users accessing the Web UI may see, in a banner, the warning "Bitbucket Server is reaching resource limits"
• The atlassian-bitbucket.log file may contain warnings such as "A [scm-hosting] ticket could not be acquired (0/12)"

Note: This bug describes a problem that occurs during startup, with symptoms occurring immediately following startup. It would be easy to confuse these symptoms with normal hosting ticket exhaustion that can occur under high load.

Solution
Upgrade to a version containing the fix

Workaround
Restarting Bitbucket Server on the affected instance is required. The window in which incoming SSH requests can be impacted by this is very small, typically only a few seconds. A system under heavy sustained load will be more susceptible to this problem and it may become necessary to block incoming network connections (to port 7999, the default Bitbucket Server SSH port) in order for the instance to start correctly.