gradle-build-cache

Simple configuration of Gradle build cache.

Reference: https://docs.gradle.com/enterprise/tutorials/caching/
Reference: https://docs.gradle.org/current/userguide/build_cache.html

preface

The Gradle build cache is a cache mechanism that aims to save time by reusing outputs produced by other builds. The build cache works by storing (locally or remotely) build outputs and allowing builds to fetch these outputs from the cache when it is determined that inputs have not changed, avoiding the expensive work of regenerating them.

A first feature using the build cache is task output caching. Essentially, task output caching leverages the same intelligence as up-to-date checks that Gradle uses to avoid work when a previous local build has already produced a set of task outputs. But instead of being limited to the previous build in the same workspace, task output caching allows Gradle to reuse task outputs from any earlier build in any location on the local machine. When using a shared build cache for task output caching this even works across developer machines and build agents.

enabling build cache

By default, the build cache is not enabled. To enable it: put org.gradle.caching=true in gradle.properties.

When the build cache is enabled, it will store build outputs in the Gradle user home.

manual

1. enable build cache (gradle.properties)
   org.gradle.caching=true
2. configure build cache (settings.gradle)

   buildCache {
       local(DirectoryBuildCache) {
           directory = new File(rootDir, 'build-cache') // custom project's directory
           removeUnusedEntriesAfterDays = 30
       }
   }
   

3. run build for the first time

   > Task :compileJava
   > Task :processResources NO-SOURCE
   > Task :classes
   > Task :jar
   > Task :assemble
   > Task :compileTestJava NO-SOURCE
   > Task :processTestResources NO-SOURCE
   > Task :testClasses UP-TO-DATE
   > Task :test NO-SOURCE
   > Task :check UP-TO-DATE
   > Task :build
   

4. delete build directory
5. run build again

   > Task :compileJava FROM-CACHE
   > Task :processResources NO-SOURCE
   > Task :classes UP-TO-DATE
   > Task :jar
   > Task :assemble
   > Task :compileTestJava NO-SOURCE
   > Task :processTestResources NO-SOURCE
   > Task :testClasses UP-TO-DATE
   > Task :test NO-SOURCE
   > Task :check UP-TO-DATE
   > Task :build
   

   Remark: compileJava is taken from cache

• For educational purposes we've committed exemplary build-cache directory.

summary

1. Between consecutive runs of a Gradle build by developers, usually not many things change. The Gradle incremental build feature will only execute the tasks that are not up-to-date anymore since they were last executed.
2. Developers typically maintain many workspaces on many branches to perform logically distinct tasks. The local cache allows outputs to be quickly reused across workspaces and branches without having to transit any networks.
3. Oftentimes, CI nodes and developers run the same tasks with the same set of changes. The remote cache allows outputs to be reused across users and build agents, ensuring your team never has to build the same thing twice.