make the plugin threadSafe

hi, when using maven to build multiple projects, you can ask to run the build in parallel by -TX when X is the number of threads.

when a plugin is not thread-safe the build will take more time to run. from maven build output:

[WARNING] * Your build is requesting parallel execution, but project      *
[WARNING] * contains the following plugin(s) that are not marked as       *
[WARNING] * @threadSafe to support parallel building.                     *
[WARNING] * While this /may/ work fine, please look for plugin updates    *
[WARNING] * and/or request plugins be made thread-safe.                   *
[WARNING] * If reporting an issue, report it against the plugin in        *
[WARNING] * question, not against maven-core                              *
[WARNING] *****************************************************************
[WARNING] The following plugins are not marked @threadSafe in MyProject:
[WARNING] com.github.eirslett:frontend-maven-plugin:0.0.20
[WARNING] *****************************************************************

is frontend-maven-plugin thread-safe? seems like marking a plugin as thread-safe is easy. can we do that?

[mtraynham]

I’ve been getting this warning since 1.5 as well.

Personally, I think we should mark all plugins as threadSafe, even the Yarn goal. What Maven means by “thread safe” here implies that the plugin goal can be run concurrently on multiple modules (i.e. directories). This is not necessarily a problem with single modules as all goals still run synchronously within that module.

It’s usually ok to have two submodule Gulp/Grunt processes running at the same time, as long as they are acting on different modules and not influencing each other. On the contrary, it’s not ok to have multiple Yarn processes running at the same time as the Yarn cache could be altered for one project and have effect on another. There is a Yarn workaround, which is to use a mutex file as suggested here.

Because it’s up to the user to run concurrently with the -T flag, and there is a Yarn workaround, I would suggest just marking all goals as threadSafe.

#466 is strange because two maven modules are sharing node/npm installs, which seems somewhat counter productive to Maven which silo’s modules by nature.

[mriehema]

Yes please and feel free to open a pull request with a fix.