A heads up about maven 3 and -T...

Simeon Pinder spinder at redhat.com
Thu Jan 20 00:08:53 UTC 2011


Hi all,

  This is a heads up to anyone running maven3 and using the -T N "threading" functionality to get greater performance out of their maven builds. It is admittedly an experimental feature and I was using it to shave serial build times down from 15 mins to as low as 6 minutes while running multiple build threads on multi-core boxes. Yeah .. if you build a lot it's quite tempting.  With that being said, things were fine for the last two months until last Thursday when builds of master started completing without errors, but on start up you'd get 

i)an empty Dashboard (due to some hidden and non-descript NPE SmartGWT javascript error)

   or on a second multi-core box 

ii)random metadata issues for missing Bundle components at startup.

See here for more details: https://bugzilla.redhat.com/show_bug.cgi?id=669729

These issues spontaneously appeared and disappeared after countless hours debugging with no source code changes.  It took quite a bit before I had eliminated most other options and finally started running maven3 in serial build mode again.  After which I have not seen any further strangeness. 

In the hopes of saving anyone else this difficulty I'd suggest you avoid -T until all the associated plugins come out with 'Thread safe' versions or at the very least if you begin to see strangeness to remember to drop down to serial mode when things look too strange.  


-Simeon


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