Incremental compilation

As of v2.7.0, an incremental compilation feature has been added that enables the plugin to detect whether sources and dependencies have changed since the last build. If sources and dependencies have not changed, then protoc will not be re-invoked.

It is worth noting that incremental compilation will not be used if you request generation of descriptor files. In this case, it may be sensible to consider splitting your definitions out into a separate Maven module.

As of v2.8.0, this feature is enabled by default.

Including/excluding file patterns

For a way to quickly include or exclude sources based upon a glob during development, you can utilise the includes and excludes parameters. This enables you to temporarily reduce the number of files that you are passing to protoc on clean builds if you are not using incremental compilation.

Compile using ECJ rather than javac

Another way of improving build speeds is to switch out javac with the Eclipse Java Compiler backend for maven-compiler-plugin. This appears to reduce compilation times by around 25% for very large projects.

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-compiler-plugin</artifactId>

  <configuration>
    <compilerId>eclipse</compilerId>
    <!-- ECJ raises warnings we do not care about in the generated code. -->
    <failOnWarning>false</failOnWarning>
    <showWarnings>false</showWarnings>
  </configuration>

  <dependencies>
    <dependency>
      <groupId>org.codehaus.plexus</groupId>
      <artifactId>plexus-compiler-eclipse</artifactId>
      <version>%VERSION%</version>
    </dependency>
  </dependencies>
</plugin>

Note that you may see new warnings, as ECJ tends to be much more vocal by default than javac.

Move proto files into a separate module

If you are pairing your proto files with your application logic, you may find your project has a large number of files in it, which will hinder build speeds. You can always consider moving your proto files into a separate Maven project that you only rebuild when the proto files change. By doing this, you can just reference the generated code as a dependency.

Skipping plugin invocation entirely

If you do not want the plugin to run at all, you can invoke Maven with the -Dprotobuf.skip flag. This will skip the invocation of this plugin entirely.

Limiting the JIT compiler

You may find overall performance improvements in Maven by passing -XX:+TieredCompilation -XX:TieredStopAtLevel=1 in your .mvn/jvm.config file in the root directory of your project, as this will disable the level 2 server JIT compiler that is enabled by default on most JDK distributions.

Tuning internal concurrency

If you wish to have further control over concurrency, you can pass the -Dprotobuf.executor.maxThreads=80 JVM flag within the .mvn/jvm.config file in the root directory of your project. This can be assigned an integer value to increase or decrease the number of threads used internally. This is not configurable via the plugin configuration itself, and is subject to change at any time.

It is worth noting that this setting is separate to the -T/--threads flag that controls the overall concurrency for the Maven build.