Hi Dan, Would the multithreading feature make it easier or harder to implement something like [1], ie distribute the different modules of a reactor build across different machines ? Or is it completely unrelated you think ?
Thanks, Jorg Heymans [1] http://n4.nabble.com/New-plugin-to-distribute-maven-jobs-steps-td585138.html#a585138 On Tue, Nov 10, 2009 at 4:02 AM, Dan Fabulich <d...@fabulich.com> wrote: > > On Friday I was playing cowboy with my experimental thread support, but > here's a more formal proposal around parallel project support in Maven 3.0. > > OUTSTANDING ISSUES > > In my earlier revision 833566, I attempted to fix MNG-3004: > > "Allow build lifecycle to execute projects in parallel" > http://jira.codehaus.org/browse/MNG-3004 > > The general consensus around this bug (which has 25 votes) is that > multithreading support can't work correctly right now because of MNG-2802: > > "Concurrent-safe access to local Maven repository" > http://jira.codehaus.org/browse/MNG-2802 > > Several people have remarked in comments to MNG-3004 that it's appropriate > to try to fix MNG-3004 (parallel projects) without fixing MNG-2802 > (thread-safe local repo). In doing so, we'll allow users to optionally > enable building multiple projects simultaneously. This is worth doing, > because it can be tested in the wild, and because for some users, it will be > immediately useful (e.g. especially if you use --offline mode). > > I agree with these comments, and attempted to implement them in revision > 833566. > > MY PROPOSAL > > I attempted to check in the code in time for 3.0-alpha-3 a few days ago. > That code was rolled back over the weekend and now lives in the MNG-3004 > branch, because it broke integration tests. All integration tests now pass > on my machine with the MNG-3004 branch, so I'd like to land it back in trunk > again and re-cut 3.0-alpha-3 with this additional feature. > > As I stated on Friday, using the MNG-3004 branch, you can now do this: > > mvn install -Dmaven.threads.experimental=4 > > It works on my machine. If it works for you great; if it doesn't, we can > figure out what's wrong together. > > WHY ALPHA-3? > > I'd like to land it back in alpha-3 because: > * alpha-2 was in February; I don't want to wait for even four months to > start testing this in the wild > * I did check it in before alpha-3 was released, but it was rolled back > quickly before the release vote was called > * Otherwise I'd want to try to release alpha-4 immediately after alpha-3, > which seems wasteful > > A NOTE ABOUT DEFAULTS > > Currently the code defaults to maven.threads.experimental=1. This fires up > a single executor thread who does all work; the main thread joins to wait > for it to finish. It's also possible to set maven.threads.experimental=0, > in which case everything is done on the main thread, just like in alpha-2. > > If there is consensus, I'd be happy to set the default value to 0, though > that increases the risk that the multithreaded code will get less coverage > in the wild. I think leaving the value at 1 is a good compromise between > avoiding complex threading issues and exercising tricky code. > > WHAT'S IN THE FUTURE? > > Post alpha-3 I'm keen on implementing a settings.xml option allowing users > to configure their local repository layout. This will allow users to choose > an alternate implementation that is thread-safe. > > Additionally, I think that this feature needs more tooling to make parallel > projects understandable. The logger should be enhanced to identify which > projects are logging which messages, and the final output of Maven should > report more clearly which projects had warning/error messages, and how many > such messages were reported. > > What do you say? > > -Dan > > --------------------------------------------------------------------- > To unsubscribe, e-mail: dev-unsubscr...@maven.apache.org > For additional commands, e-mail: dev-h...@maven.apache.org > > --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@maven.apache.org For additional commands, e-mail: dev-h...@maven.apache.org
