[MRESOLVER-132] Remove synchronization in TrackingFileManager

[michael-o]

See motivation in the ticket as well as the call hierarchy: https://issues.apache.org/jira/browse/MRESOLVER-132

[michael-o]

@elharo I'd gently reuse my statement here for the Manager: #66 (comment). We can create a separate issue to improve the code.

[michael-o]

@dantran Could you also kindly try this one for you. In my opinion this removes unnecessary locks. Use the same project as for the Redisson solution, but w/o Redisson.

[dantran]

@michael-o I build MRESOLVER-132 branch together with maven 3.6.3 tag from the source. Still see the slow build.

* 60min+ versus 5 min using original maven 3.6.3

[michael-o]

@michael-o Did you leave out any additional SyncContextFactory? I guess not. I expect that this change should actually improve performance with the bundled DefaultSyncContextFactory. This one is not necessary related to MRESOLVER-131.

[dantran]

@michael-o, mine is a clean build only involves this branch ( ie no SyncContextFactory)

It is 10 minutes faster when using pure maven-resolver-1.5.1-SNAPSHOT at master

[michael-o]

@dantran Thanks, if is supposed to be faster. This unnecessary sync is gone.

[eolivelli]

LGTM

I left one little suggestion for an improvement, it could be significant on slow FS and probably more on Windows
Btw the change is good even in this form

[eolivelli]

Makes sense.

+1

[jira-importer]

Resolve #896

[jira-importer]

Resolve #896