David Santiago created JENKINS-12763:
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Summary: Excessive lock contention when using mercurial cache with
multiple repos and slaves
Key: JENKINS-12763
URL: https://issues.jenkins-ci.org/browse/JENKINS-12763
Project: Jenkins
Issue Type: Improvement
Components: mercurial
Affects Versions: current
Reporter: David Santiago
Assignee: Kohsuke Kawaguchi
The current implementation of the mercurial plugin uses a too aggressive
locking approach for managing its cache across master and build slaves.
By aggressive I mean that whenever a build starts for a given repository on any
given build slave, it will block any subsequent build of any other jobs which
share the same repository while it updates the cache in both the master and the
slave used for the build, and also creates its working directory. With multiple
jobs which share repositories (through different branches, for instance), lock
contention ramps up.
This is not necessary, as a different locking mechanism can be used to allow
concurrent builds of jobs which share the same repository but run in different
slaves. It can be achieved by using different locks for controlling the updates
of master and slave nodes caches.
This way, we reduce lock contention and increase cache update performance.
A pull request has been created for this:
https://github.com/jenkinsci/mercurial-plugin/pull/21
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