maven-parallel-not-enabled

Detects multi-module Maven repositories that run lifecycle goals in CI without parallel module execution.

Why it matters

Maven builds modules serially by default. For multi-module projects, --threads lets independent modules build and test in parallel, which can substantially reduce CI wall-clock time. Many repositories run large Maven builds with the default single-threaded configuration.

Detection

Reports when:

• The repository uses Maven (pom.xml or mvnw)
• CI executes a Maven lifecycle goal (compile, test, package, verify, install, deploy, integration-test)
• The build looks multi-module: the root pom.xml declares <modules>, or more than one pom.xml is present
• At least one CI Maven lifecycle command lacks -T / --threads, and root .mvn/maven.config does not configure parallel execution

Exclusions

Does not report when:

• Every CI Maven lifecycle command passes -T or --threads, or parallel execution is configured in .mvn/maven.config (commented flags do not count). A tuned command does not suppress a separate untuned command or job.
• Only a single pom.xml is found and the root POM has no <modules>
• No Maven lifecycle goal runs in CI

Severity

warning — parallel execution is a large, low-risk win for most multi-module builds, but plugins that are not marked @threadSafe can break under parallelism.

Caveats

Always check Maven’s thread-safety warnings (it lists plugins whose goals are not marked @threadSafe). Replace or isolate those plugins before relying on parallel execution, and validate the build and test results.