Built by Maven

Getting Started

To on-board incremental Maven you need to complete several steps:

  • Declare caching extension in your project (either in pom.xml or .mvn/extensions.xml)
  • Add maven-build-cache-config.xml cache config in .mvn/ (optional) to customize default behavior
  • Validate build results and iteratively, adjust config to properly reflect project specifics
  • Setup remote cache (optional)

Declaring build cache extension

<extension>
    <groupId>org.apache.maven.extensions</groupId>
    <artifactId>maven-build-cache-extension</artifactId>
    <version>1.0.0-SNAPSHOT</version>
</extension>

either in pom.xml's <project>/<build>/<extensions> or in .mvn/extensions.xml's <extensions>

Adding build cache config

Copy template config maven-build-cache-config.xml to .mvn/ directory of your project.
To get overall understanding of build cache machinery, it is recommended to review the config and read comments. In typical scenario you need to:

  • Exclude unstable, temporary files or environment specific files
  • Add plugins reconciliation rules – add critical plugins parameters to reconciliation
  • Configure precise source code files selectors. Though source code locations discovered automatically from project and plugins config, there might be edge cases.
  • Add remote cache location (if remote cache is used)

Adjusting build cache config

Having extension run usual command, like mvn package. Verify the caching engine is activated:

  • Check log output - there should be cache related output or initialization error message: 
    [INFO] Loading cache configuration from <project dir>/.mvn/maven-build-cache-config.xml
  • Navigate to your local repo directory - there should be a sibling directory cache next to the usual local repository.
  • Find buildinfo.xml in the cache repository for typical module and review it. Ensure that
    • expected source code files are present in the build info
    • Review all plugings used in the build and add their critical parameters to reconciliation

It is recommended to find the best working trade-off between fairness and cache efficiency. Adding unnecessary rules and checks could reduce both performance and cache efficiency (hit rate).

Adding caching CI and remote cache

To leverage remote cache feature there should a shared storage provide. Any technology supported by Maven Resolver will suffice. In simplest form it could be a http web server which supports get/put operations (Nginx OSS with fs module or any other equivalent). See Remote cache setup for detailed description of cache setup.