[AURON #2020] [BUILD] Add --threads option to control Maven build parallelism.

[slfan1989]

Which issue does this PR close?

Closes #2020

Rationale for this change

Currently, local builds are always single-threaded, which can be slow on multi-core machines. Docker builds hardcode -T8, which cannot be overridden by users. This change adds a --threads option to auron-build.sh to give users control over Maven build parallelism.

What changes are included in this PR?

1. auron-build.sh

   • Added --threads parameter parsing and validation
   • Unified thread configuration logic: user-specified value takes precedence, Docker defaults to 8 threads, local defaults to single-threaded
   • Removed hardcoded -T8 from Docker build section
   • Updated help text to document the new option

2. CONTRIBUTING.md

   • Documented --threads option under Build Options section
   • Described default behavior for local vs Docker builds

Are there any user-facing changes?

Yes. Users can now specify --threads to control Maven build parallelism

Default behavior remains unchanged (backward compatible):

• Local builds: single-threaded
• Docker builds: 8 threads

How was this patch tested?

• Verified ./auron-build.sh --help displays correct usage information

[slfan1989]

./auron-build.sh --pre --sparkver 4.1 --scalaver 2.13 --threads 2

[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary for Apache Auron Parent Pom 7.0.0-incubating:
[INFO] 
[INFO] Apache Auron Parent Pom ............................ SUCCESS [ 11.384 s]
[INFO] Apache Auron Proto ................................. SUCCESS [ 28.548 s]
[INFO] Apache Auron Hadoop Shim 2.13 ...................... SUCCESS [  8.290 s]
[INFO] Apache Auron Core .................................. SUCCESS [  9.705 s]
[INFO] Apache Auron Common 2.13 ........................... SUCCESS [ 15.309 s]
[INFO] Apache Auron Spark Version Annotation Macros 2.13 .. SUCCESS [  6.961 s]
[INFO] Apache Auron Spark UI 2.13 ......................... SUCCESS [  6.463 s]
[INFO] Apache Auron Spark Extension 2.13 .................. SUCCESS [ 35.552 s]
[INFO] Apache Auron Spark Extension Shims Spark 4.1.1_2.13  SUCCESS [ 28.957 s]
[INFO] Apache Auron Assembly .............................. SUCCESS [ 12.828 s]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  02:07 min (Wall Clock)
[INFO] Finished at: 2026-02-18T14:00:14+08:00
[INFO] ------------------------------------------------------------------------

./auron-build.sh --pre --sparkver 4.1 --scalaver 2.13 --threads 4

[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary for Apache Auron Parent Pom 7.0.0-incubating:
[INFO] 
[INFO] Apache Auron Parent Pom ............................ SUCCESS [  6.504 s]
[INFO] Apache Auron Proto ................................. SUCCESS [ 25.801 s]
[INFO] Apache Auron Hadoop Shim 2.13 ...................... SUCCESS [ 10.265 s]
[INFO] Apache Auron Core .................................. SUCCESS [  8.988 s]
[INFO] Apache Auron Common 2.13 ........................... SUCCESS [ 14.699 s]
[INFO] Apache Auron Spark Version Annotation Macros 2.13 .. SUCCESS [  6.991 s]
[INFO] Apache Auron Spark UI 2.13 ......................... SUCCESS [  6.127 s]
[INFO] Apache Auron Spark Extension 2.13 .................. SUCCESS [ 26.319 s]
[INFO] Apache Auron Spark Extension Shims Spark 4.1.1_2.13  SUCCESS [ 25.859 s]
[INFO] Apache Auron Assembly .............................. SUCCESS [ 14.000 s]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  01:47 min (Wall Clock)
[INFO] Finished at: 2026-02-18T14:02:31+08:00
[INFO] ------------------------------------------------------------------------

[Copilot]

Pull request overview

Adds a new --threads option to auron-build.sh so users can control Maven parallelism, removing the previously hardcoded Docker -T8 behavior while keeping existing defaults (local single-threaded; Docker defaults to 8 threads).

Changes:

• Add --threads CLI option, plumbed into Maven -T handling with precedence: user-specified > Docker default (8) > local default (unset).
• Remove the Docker-only hardcoded -T8 addition and centralize thread selection in one place.
• Document the new option and defaults in CONTRIBUTING.md.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
auron-build.sh	Adds --threads parsing and centralizes Maven -T argument selection for local vs Docker builds.
CONTRIBUTING.md	Documents the new --threads build option and default behavior.

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[ShreyeshArangath]

Single thread for local builds might be too low, should we at least do 4? If machines are not able to handle it (seems like the edge case to me), they can always tune it.

[slfan1989]

Thanks for the review! I think it's safer to keep the default at 1 thread in this PR to match the current behavior. We can bump it to 4 (or more) in a separate follow-up PR once this lands. Does that sound reasonable to you?

[ShreyeshArangath]

That's fair, thanks