sky

I'm sorry it's hard to reproduce. I try to rerun a project 50 times per group in serveral groups and sometimes it appears. I'm working on the compatiablity of mvnd...

according to #310 and [DefaultMavenPluginManager](https://github.com/apache/maven/blob/maven-3.2.5/maven-core/src/main/java/org/apache/maven/plugin/internal/DefaultMavenPluginManager.java), I roll back the 'synchronized' keywords and this exception gone in maven 3.2.5. Maybe we can keep collectioning samples and see whether this issue reappear...

> > according to #310 and [DefaultMavenPluginManager](https://github.com/apache/maven/blob/maven-3.2.5/maven-core/src/main/java/org/apache/maven/plugin/internal/DefaultMavenPluginManager.java), I roll back the 'synchronized' keywords and this exception gone in maven 3.2.5. > > Maybe we can keep collectioning samples and see...

Raise the keep-alive timeout seems to no effects now. https://github.com/lanmaoxinqing/mvnd/runs/2902075523?check_suite_focus=true#step:7:1100

> See #384. My original idea was to be able to support multiple maven versions managed from the same `mvnd` version. Kinda like daemons are spawned according to the JDK,...