Cache Intelligence

Modern continuous integration systems execute pipelines inside ephemeral environments that are provisioned solely for pipeline execution and are not reused from prior pipeline runs. As builds often require downloading and installing many library and software dependencies, caching these dependencies for quick retrieval at runtime can save a significant amount of time.

There are several ways to configure caching in Harness CI: save and restore cache steps, mounting volumes, and Cache Intelligence. Mounting volumes or using save and restore cache steps requires you to manage the cache. With Cache Intelligence, Harness automatically caches and restores common dependencies. Also, you don't need to bring your own storage with Cache Intelligence, because we store the cache in our hosted environment, Harness Cloud.

Supported build infrastructures and tools

Currently, Cache Intelligence is available only when using Harness Cloud, the Harness-hosted build environment.

Currently, Cache Intelligence supports Bazel, Maven, Gradle, Yarn, Go, and Node build tools. The dependencies must be stored in the default location for the tool used.

If you are using a different build tool or a non-default cache location, you can still leverage Harness' cache storage by specifying the location(s) to cache.

Cache storage

Harness Cloud allows up to 2GB of cache storage per account. All pipelines in the account use the same cache storage, and each build tool has a unique cache key that is used to restore the appropriate cache data at runtime.

The cache retention window is 15 days, which resets whenever the cache is updated.

Enable Cache Intelligence

To enable Cache Intelligence on a CI Build stage, add the following lines to the stage: spec: in your pipeline's YAML:

caching:
  enabled: true

For example:

    - stage:
        name: Build Jhttp
        identifier: Build_Jhttp
        type: CI
        spec:
          caching:
            enabled: true
          cloneCodebase: true
...

Customize cache paths

Cache Intelligence stores the data to be cached in the /harness directory by default. You can use paths to specify a list of locations to be cached. This is useful if:

Cache Intelligence is not supported for your build tool.
You have customized cache locations, such as with yarn config set cache-folder.

Add the paths list to your pipeline's YAML, for example:

    - stage:
        name: Build
        identifier: Build
        type: CI
        spec:
          caching:
            enabled: true
            paths:
              - /harness/node_modules
          cloneCodebase: true
...

If a path you want to cache is outside the /harness directory, you must also specify this as a shared path. In the YAML editor, add a list of sharedPaths to the stage: spec:, for example:

    - stage:
        name: Build
        identifier: Build
        type: CI
        spec:
          caching:
            enabled: true
            paths:
              - /harness/node_modules
              - /my_cache_directory/module_cache1
          cloneCodebase: true
          execution:
            steps:
...
          platform:
            os: Linux
            arch: Amd64
          runtime:
            type: Cloud
            spec: {}
          sharedPaths:
            - /my_cache_directory/module_cache1

In the Visual editor, you can add Shared Paths in the stage's Overview settings. However, you must use the YAML editor to enable caching and specify paths.

Customize cache keys

Harness generates a cache key from a hash of the build lock file (such as pom.xml, build.gradle, or package.json) that Harness detects. If Harness detects multiple tools or multiple lock files, Harness combines the hashes to create the cache key.

To customize the cache key, add key: [custom-key] to stage: spec: caching: in your pipeline's YAML, and specify the custom key value. You can use fixed values, runtime inputs, and expressions to create the key value.

The following YAML example uses key: <+input>, which prompts the user to supply a cache key value at runtime.

    - stage:
        name: Build
        identifier: Build
        type: CI
        spec:
          caching:
            enabled: true
            key: <+input>
          cloneCodebase: true
...