We have a large Jenkins installation with > 4000 MavenModuleSet builds and each one has about 10-20 MavenModule childs.

When we see the line "Modules changed, recalculating dependency graph" in our build log it can take 30-120 minutes till the dependency graph is calculated. 

The Build Job is executed on a build slave.

In our Jenkins Master we did a jstack to get thread dumps during the calculation of the dependency graph.

The thread dumps look like this for most of the time:

"Executor #0 for Slave201 : executing test-modularisierung #7" #10378302 daemon prio=5 os_prio=0 tid=0x00007f1ead3c5800 nid=0x91a runnable [0x00007f1ebe461000]

   java.lang.Thread.State: RUNNABLE

        at com.google.common.collect.AbstractMultimap.put(AbstractMultimap.java:203)

        at com.google.common.collect.AbstractSetMultimap.put(AbstractSetMultimap.java:117)

        at com.google.common.collect.HashMultimap.put(HashMultimap.java:49)

        at hudson.maven.MavenModule$MavenDependencyComputationData.byName(MavenModule.java:703)

        at hudson.maven.MavenModule$MavenDependencyComputationData.access$100(MavenModule.java:682)

        at hudson.maven.MavenModule.buildDependencyGraph(MavenModule.java:555)

        at hudson.model.DependencyGraph.build(DependencyGraph.java:92)

        at jenkins.model.Jenkins.rebuildDependencyGraph(Jenkins.java:4709)

        at hudson.maven.MavenModuleSetBuild$MavenModuleSetBuildExecution.parsePoms(MavenModuleSetBuild.java:1059)

        at hudson.maven.MavenModuleSetBuild$MavenModuleSetBuildExecution.doRun(MavenModuleSetBuild.java:691)

        at hudson.model.AbstractBuild$AbstractBuildExecution.run(AbstractBuild.java:504)

        at hudson.model.Run.execute(Run.java:1880)

        at hudson.maven.MavenModuleSetBuild.run(MavenModuleSetBuild.java:543)

        at hudson.model.ResourceController.execute(ResourceController.java:97)

        at hudson.model.Executor.run(Executor.java:428)

MavenDependencyComputationData.byName is very expensive in our case. Would it be possible to cache the MultiMap in MavenDependencyComputationData?