[MNG-6774] - Speedup project graph build by paralleling operations

[AlexanderAshitkin]

Initial implementation of DefaultGraphBuilder is single threaded and doesn't scale on multi-core servers/workstations.
The proposal is to use fork join pool to build the project graph - as per initial result, graph build time reduced ~2.5 times with -T4 from 14..15 to 5..6 sec

Implementation is rather trivial - current implementation walks projects tree in depth which is naturally fits fork join model - sub-modules are forked and joined to get final result

Risks: mostly mutable objects in domain model and non-functional initial implementation.
Safety could be improved with model rework to immutable model.

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[eolivelli]

Cool.
Do you have any number to share ?

[AlexanderAshitkin]

Hi
so far on my project in conjunction with #288 i achieved speedup from 14..15 seconds to 5..6 seconds .

I also tested apache wicket and results are follwing:
Old -T1
[main] Phase 1: 1406
[main] Phase 2: 6539
[main] Project graph built in: 7958

New -T1
[main] Phase 1: 1413
[main] Phase 2: 2450 (*difference is due to #288)
[main] Project graph built in: 3877

New -T2
[ForkJoinPool-1-worker-1] Phase 1: 845
[ForkJoinPool-1-worker-1] Phase 2: 2443
[main] Project graph built in: 3304

New -T4
[ForkJoinPool-1-worker-1] Phase 1: 955
[ForkJoinPool-1-worker-1] Phase 2: 2642
[main] Project graph built in: 3613

New -T8
[ForkJoinPool-1-worker-1] Phase 1: 1007
[ForkJoinPool-1-worker-1] Phase 2: 2578
[main] Project graph built in: 3608

[filipwiech]

Hello, any update on this?

[eolivelli]

Sorry.
I forgot about this change.
Your numbers looks promising.
I will take a new look

[eolivelli]

Great work.
I left a few comments

We are going to move master to java 8 so we could use lambda but we have to wait for @rfscholte commit

[AlexanderAshitkin]

rebased on top of current master (3.7.0-SNAPSHOT)

[maximilian-novikov-db]

any updates please, when it can be merged ?