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From Fabian van der Veen <>
Subject Re: Hickup in multi thread build
Date Mon, 02 May 2016 06:55:16 GMT
Hey Dan,

I think I've seen my extension still fail a few times as well, but it wasn't reproducible
enough to debug for me. It is still a concurrency issue amongst the other problems; so it
could simply be something I assumed thread-safe API actually isn't thread-safe at all. (Which
opens another interesting dimension of problems, should that be true...)
On the other hand, I decided to tackle the core problem in our build instead: removing aggregating
plugin executions from anything but the root pom.

It might be a lot of work, but given how these plugins resolve their dependencies, it might
be for the best. (Besides the fact that, if I recall correctly, these kinds of plugins are
described as aggregating data from the entire project.)
For example, in our case the javadoc plugin (amongst others) had the aggregate goals declared
in the root pom, but - unfortunately - these goals simply get inherited to all child poms
as well (causing the mentioned problems).

What we did was simply run the help:effective-pom target on the projects (randomly) failing
in a concurrent build; and check for all the resulting plugin executions whether or not that
goal was an aggregate goal or not. With the list of offending plugins ready, we removed those
that were configured wrongly by developers. The ones left, we configured with "<inherited>false</inherited>"
in the plugin definition in the root pom; which makes the plugin only configured and run on
the parent.

Actually working through the poms and fixing the offenders has made our concurrent build 100%
stable again. So while the extension does - in our case, at least - certainly improve stability;
it's still (unfortunately) not a complete (easy) workaround.

Hopefully this'll help you get your build stable again as well. Otherwise, it'll be a waiting
game until the issues I mentioned are picked up.

- Fabian

On vr, 2016-04-29 at 17:04 -0700, Dan Tran wrote:

I dont see much improvement. I am seeing  2-3 fail build a day


On Wed, Apr 20, 2016 at 12:40 AM, Dan Tran <<>>

Hi Fabian

I will give your extension a try



On Wed, Apr 20, 2016 at 12:26 AM, Fabian van der Veen <<>> wrote:


The way you describe it; this sounds like a problem I also encountered in
our (similar sized) project here.
I reported this here:,
which has been linked as related to

Troubleshooting boiled down to running maven in debug mode; which might
be something you don't want to do.
In any case, I found that plugins running aggregate goals (e.g.
javadoc:aggregate) will resolve (compile) dependencies for _all_ projects
in the reactor. Running such a plugin in anything else than your root pom
might cause the random failures you have. (And having the plugin in your
root pom might also effectively include its configuration and execution in
child poms; which is "debuggable" using help:effective-pom.)

Hopefully this helps you.

- Fabian

On di, 2016-04-19 at 12:08 -0700, Dan Tran wrote:


My 150+ modules with multi-thread build randomly error out with something
like this

  java.lang.NoClassDefFoundError: org/slf4j/LoggerFactory

Have you encountered similar issue?  how do you troubleshoot?

I am using maven 3.3.9 and latest compiler plugin



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