603 lines
18 KiB
Markdown
603 lines
18 KiB
Markdown
---
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stage: Verify
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group: Pipeline Authoring
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info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments
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type: index, concepts, howto
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---
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# Caching in GitLab CI/CD **(FREE)**
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A cache is one or more files that a job downloads and saves. Subsequent jobs that use
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the same cache don't have to download the files again, so they execute more quickly.
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To learn how to define the cache in your `.gitlab-ci.yml` file,
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see the [`cache` reference](../yaml/index.md#cache).
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## How cache is different from artifacts
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Use cache for dependencies, like packages you download from the internet.
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Cache is stored where GitLab Runner is installed and uploaded to S3 if
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[distributed cache is enabled](https://docs.gitlab.com/runner/configuration/autoscale.html#distributed-runners-caching).
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Use artifacts to pass intermediate build results between stages.
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Artifacts are generated by a job, stored in GitLab, and can be downloaded.
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Both artifacts and caches define their paths relative to the project directory, and
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can't link to files outside it.
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### Cache
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- Define cache per job by using the `cache:` keyword. Otherwise it is disabled.
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- Subsequent pipelines can use the cache.
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- Subsequent jobs in the same pipeline can use the cache, if the dependencies are identical.
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- Different projects cannot share the cache.
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### Artifacts
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- Define artifacts per job.
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- Subsequent jobs in later stages of the same pipeline can use artifacts.
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- Different projects cannot share artifacts.
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- Artifacts expire after 30 days by default. You can define a custom [expiration time](../yaml/index.md#artifactsexpire_in).
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- The latest artifacts do not expire if [keep latest artifacts](../pipelines/job_artifacts.md#keep-artifacts-from-most-recent-successful-jobs) is enabled.
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- Use [dependencies](../yaml/index.md#dependencies) to control which jobs fetch the artifacts.
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## Good caching practices
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To ensure maximum availability of the cache, do one or more of the following:
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- [Tag your runners](../runners/configure_runners.md#use-tags-to-control-which-jobs-a-runner-can-run) and use the tag on jobs
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that share the cache.
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- [Use runners that are only available to a particular project](../runners/runners_scope.md#prevent-a-specific-runner-from-being-enabled-for-other-projects).
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- [Use a `key`](../yaml/index.md#cachekey) that fits your workflow. For example,
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you can configure a different cache for each branch.
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For runners to work with caches efficiently, you must do one of the following:
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- Use a single runner for all your jobs.
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- Use multiple runners that have
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[distributed caching](https://docs.gitlab.com/runner/configuration/autoscale.html#distributed-runners-caching),
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where the cache is stored in S3 buckets. Shared runners on GitLab.com behave this way. These runners can be in autoscale mode,
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but they don't have to be.
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- Use multiple runners with the same architecture and have these runners
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share a common network-mounted directory to store the cache. This directory should use NFS or something similar.
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These runners must be in autoscale mode.
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## Use multiple caches
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> - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/32814) in GitLab 13.10.
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> - [Feature Flag removed](https://gitlab.com/gitlab-org/gitlab/-/issues/321877), in GitLab 13.12.
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You can have a maximum of four caches:
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```yaml
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test-job:
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stage: build
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cache:
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- key:
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files:
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- Gemfile.lock
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paths:
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- vendor/ruby
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- key:
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files:
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- yarn.lock
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paths:
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- .yarn-cache/
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script:
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- bundle install --path=vendor
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- yarn install --cache-folder .yarn-cache
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- echo Run tests...
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```
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If multiple caches are combined with a fallback cache key,
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the fallback cache is fetched every time a cache is not found.
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## Use a fallback cache key
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> [Introduced](https://gitlab.com/gitlab-org/gitlab-runner/-/merge_requests/1534) in GitLab Runner 13.4.
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You can use the `$CI_COMMIT_REF_SLUG` [predefined variable](../variables/predefined_variables.md)
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to specify your [`cache:key`](../yaml/index.md#cachekey). For example, if your
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`$CI_COMMIT_REF_SLUG` is `test`, you can set a job to download cache that's tagged with `test`.
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If a cache with this tag is not found, you can use `CACHE_FALLBACK_KEY` to
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specify a cache to use when none exists.
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In the following example, if the `$CI_COMMIT_REF_SLUG` is not found, the job uses the key defined
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by the `CACHE_FALLBACK_KEY` variable:
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```yaml
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variables:
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CACHE_FALLBACK_KEY: fallback-key
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job1:
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script:
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- echo
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cache:
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key: "$CI_COMMIT_REF_SLUG"
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paths:
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- binaries/
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```
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## Disable cache for specific jobs
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If you define the cache globally, each job uses the
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same definition. You can override this behavior for each job.
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To disable it completely for a job, use an empty hash:
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```yaml
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job:
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cache: []
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```
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## Inherit global configuration, but override specific settings per job
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You can override cache settings without overwriting the global cache by using
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[anchors](../yaml/index.md#anchors). For example, if you want to override the
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`policy` for one job:
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```yaml
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cache: &global_cache
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key: $CI_COMMIT_REF_SLUG
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paths:
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- node_modules/
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- public/
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- vendor/
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policy: pull-push
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job:
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cache:
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# inherit all global cache settings
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<<: *global_cache
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# override the policy
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policy: pull
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```
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For more information, see [`cache: policy`](../yaml/index.md#cachepolicy).
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## Common use cases for caches
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Usually you use caches to avoid downloading content, like dependencies
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or libraries, each time you run a job. Node.js packages,
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PHP packages, Ruby gems, Python libraries, and others can be cached.
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For examples, see the [GitLab CI/CD templates](https://gitlab.com/gitlab-org/gitlab/-/tree/master/lib/gitlab/ci/templates).
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### Share caches between jobs in the same branch
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To have jobs in each branch use the same cache, define a cache with the `key: $CI_COMMIT_REF_SLUG`:
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```yaml
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cache:
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key: $CI_COMMIT_REF_SLUG
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```
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This configuration prevents you from accidentally overwriting the cache. However, the
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first pipeline for a merge request is slow. The next time a commit is pushed to the branch, the
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cache is re-used and jobs run faster.
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To enable per-job and per-branch caching:
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```yaml
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cache:
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key: "$CI_JOB_NAME-$CI_COMMIT_REF_SLUG"
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```
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To enable per-stage and per-branch caching:
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```yaml
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cache:
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key: "$CI_JOB_STAGE-$CI_COMMIT_REF_SLUG"
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```
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### Share caches across jobs in different branches
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To share a cache across all branches and all jobs, use the same key for everything:
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```yaml
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cache:
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key: one-key-to-rule-them-all
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```
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To share a cache between branches, but have a unique cache for each job:
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```yaml
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cache:
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key: $CI_JOB_NAME
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```
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### Cache Node.js dependencies
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If your project uses [npm](https://www.npmjs.com/) to install Node.js
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dependencies, the following example defines `cache` globally so that all jobs inherit it.
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By default, npm stores cache data in the home folder (`~/.npm`). However, you
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[can't cache things outside of the project directory](../yaml/index.md#cachepaths).
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Instead, tell npm to use `./.npm`, and cache it per-branch:
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```yaml
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#
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# https://gitlab.com/gitlab-org/gitlab/-/tree/master/lib/gitlab/ci/templates/Nodejs.gitlab-ci.yml
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#
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image: node:latest
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# Cache modules in between jobs
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cache:
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key: $CI_COMMIT_REF_SLUG
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paths:
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- .npm/
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before_script:
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- npm ci --cache .npm --prefer-offline
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test_async:
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script:
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- node ./specs/start.js ./specs/async.spec.js
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```
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### Cache PHP dependencies
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If your project uses [Composer](https://getcomposer.org/) to install
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PHP dependencies, the following example defines `cache` globally so that
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all jobs inherit it. PHP libraries modules are installed in `vendor/` and
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are cached per-branch:
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```yaml
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#
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# https://gitlab.com/gitlab-org/gitlab/-/tree/master/lib/gitlab/ci/templates/PHP.gitlab-ci.yml
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#
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image: php:7.2
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# Cache libraries in between jobs
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cache:
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key: $CI_COMMIT_REF_SLUG
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paths:
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- vendor/
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before_script:
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# Install and run Composer
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- curl --show-error --silent "https://getcomposer.org/installer" | php
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- php composer.phar install
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test:
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script:
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- vendor/bin/phpunit --configuration phpunit.xml --coverage-text --colors=never
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```
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### Cache Python dependencies
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If your project uses [pip](https://pip.pypa.io/en/stable/) to install
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Python dependencies, the following example defines `cache` globally so that
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all jobs inherit it. Python libraries are installed in a virtual environment under `venv/`.
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pip's cache is defined under `.cache/pip/` and both are cached per-branch:
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```yaml
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#
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# https://gitlab.com/gitlab-org/gitlab/-/tree/master/lib/gitlab/ci/templates/Python.gitlab-ci.yml
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#
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image: python:latest
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# Change pip's cache directory to be inside the project directory since we can
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# only cache local items.
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variables:
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PIP_CACHE_DIR: "$CI_PROJECT_DIR/.cache/pip"
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# Pip's cache doesn't store the python packages
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# https://pip.pypa.io/en/stable/reference/pip_install/#caching
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#
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# If you want to also cache the installed packages, you have to install
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# them in a virtualenv and cache it as well.
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cache:
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paths:
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- .cache/pip
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- venv/
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before_script:
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- python -V # Print out python version for debugging
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- pip install virtualenv
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- virtualenv venv
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- source venv/bin/activate
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test:
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script:
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- python setup.py test
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- pip install flake8
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- flake8 .
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```
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### Cache Ruby dependencies
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If your project uses [Bundler](https://bundler.io) to install
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gem dependencies, the following example defines `cache` globally so that all
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jobs inherit it. Gems are installed in `vendor/ruby/` and are cached per-branch:
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```yaml
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#
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# https://gitlab.com/gitlab-org/gitlab/-/tree/master/lib/gitlab/ci/templates/Ruby.gitlab-ci.yml
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#
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image: ruby:2.6
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# Cache gems in between builds
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cache:
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key: $CI_COMMIT_REF_SLUG
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paths:
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- vendor/ruby
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before_script:
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- ruby -v # Print out ruby version for debugging
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- bundle install -j $(nproc) --path vendor/ruby # Install dependencies into ./vendor/ruby
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rspec:
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script:
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- rspec spec
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```
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If you have jobs that need different gems, use the `prefix`
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keyword in the global `cache` definition. This configuration generates a different
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cache for each job.
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For example, a testing job might not need the same gems as a job that deploys to
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production:
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```yaml
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cache:
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key:
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files:
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- Gemfile.lock
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prefix: $CI_JOB_NAME
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paths:
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- vendor/ruby
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test_job:
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stage: test
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before_script:
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- bundle install --without production --path vendor/ruby
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script:
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- bundle exec rspec
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deploy_job:
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stage: production
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before_script:
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- bundle install --without test --path vendor/ruby
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script:
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- bundle exec deploy
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```
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### Cache Go dependencies
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If your project uses [Go Modules](https://github.com/golang/go/wiki/Modules) to install
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Go dependencies, the following example defines `cache` in a `go-cache` template, that
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any job can extend. Go modules are installed in `${GOPATH}/pkg/mod/` and
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are cached for all of the `go` projects:
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```yaml
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.go-cache:
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variables:
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GOPATH: $CI_PROJECT_DIR/.go
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before_script:
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- mkdir -p .go
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cache:
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paths:
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- .go/pkg/mod/
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test:
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image: golang:1.13
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extends: .go-cache
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script:
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- go test ./... -v -short
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```
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## Availability of the cache
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Caching is an optimization, but it isn't guaranteed to always work. You might need
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to regenerate cached files in each job that needs them.
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After you define a [cache in `.gitlab-ci.yml`](../yaml/index.md#cache),
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the availability of the cache depends on:
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- The runner's executor type.
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- Whether different runners are used to pass the cache between jobs.
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### Where the caches are stored
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All caches defined for a job are archived in a single `cache.zip` file.
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The runner configuration defines where the file is stored. By default, the cache
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is stored on the machine where GitLab Runner is installed. The location also depends on the type of executor.
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| Runner executor | Default path of the cache |
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| ---------------------- | ------------------------- |
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| [Shell](https://docs.gitlab.com/runner/executors/shell.html) | Locally, under the `gitlab-runner` user's home directory: `/home/gitlab-runner/cache/<user>/<project>/<cache-key>/cache.zip`. |
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| [Docker](https://docs.gitlab.com/runner/executors/docker.html) | Locally, under [Docker volumes](https://docs.gitlab.com/runner/executors/docker.html#the-builds-and-cache-storage): `/var/lib/docker/volumes/<volume-id>/_data/<user>/<project>/<cache-key>/cache.zip`. |
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| [Docker Machine](https://docs.gitlab.com/runner/executors/docker_machine.html) (autoscale runners) | The same as the Docker executor. |
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If you use cache and artifacts to store the same path in your jobs, the cache might
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be overwritten because caches are restored before artifacts.
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### How archiving and extracting works
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This example shows two jobs in two consecutive stages:
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```yaml
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stages:
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- build
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- test
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before_script:
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- echo "Hello"
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job A:
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stage: build
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script:
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- mkdir vendor/
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- echo "build" > vendor/hello.txt
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cache:
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key: build-cache
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paths:
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- vendor/
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after_script:
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- echo "World"
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job B:
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stage: test
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script:
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- cat vendor/hello.txt
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cache:
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key: build-cache
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paths:
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- vendor/
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```
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If one machine has one runner installed, then all jobs for your project
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run on the same host:
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1. Pipeline starts.
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1. `job A` runs.
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1. `before_script` is executed.
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1. `script` is executed.
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1. `after_script` is executed.
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1. `cache` runs and the `vendor/` directory is zipped into `cache.zip`.
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This file is then saved in the directory based on the
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[runner's setting](#where-the-caches-are-stored) and the `cache: key`.
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1. `job B` runs.
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1. The cache is extracted (if found).
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1. `before_script` is executed.
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1. `script` is executed.
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1. Pipeline finishes.
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By using a single runner on a single machine, you don't have the issue where
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`job B` might execute on a runner different from `job A`. This setup guarantees the
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cache can be reused between stages. It only works if the execution goes from the `build` stage
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to the `test` stage in the same runner/machine. Otherwise, the cache [might not be available](#cache-mismatch).
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During the caching process, there's also a couple of things to consider:
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- If some other job, with another cache configuration had saved its
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cache in the same zip file, it is overwritten. If the S3 based shared cache is
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used, the file is additionally uploaded to S3 to an object based on the cache
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key. So, two jobs with different paths, but the same cache key, overwrites
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their cache.
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- When extracting the cache from `cache.zip`, everything in the zip file is
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extracted in the job's working directory (usually the repository which is
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pulled down), and the runner doesn't mind if the archive of `job A` overwrites
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things in the archive of `job B`.
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It works this way because the cache created for one runner
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often isn't valid when used by a different one. A different runner may run on a
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different architecture (for example, when the cache includes binary files). Also,
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because the different steps might be executed by runners running on different
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machines, it is a safe default.
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## Clearing the cache
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Runners use [cache](../yaml/index.md#cache) to speed up the execution
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of your jobs by reusing existing data. This can sometimes lead to
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inconsistent behavior.
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There are two ways to start with a fresh copy of the cache.
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### Clear the cache by changing `cache:key`
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Change the value for `cache: key` in your `.gitlab-ci.yml` file.
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The next time the pipeline runs, the cache is stored in a different location.
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### Clear the cache manually
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> [Introduced](https://gitlab.com/gitlab-org/gitlab-foss/-/issues/41249) in GitLab 10.4.
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You can clear the cache in the GitLab UI:
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1. On the top bar, select **Menu > Projects** and find your project.
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1. On the left sidebar, select **CI/CD > Pipelines** page.
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1. In the top right, select **Clear runner caches**.
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On the next commit, your CI/CD jobs use a new cache.
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NOTE:
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Each time you clear the cache manually, the [internal cache name](#where-the-caches-are-stored) is updated. The name uses the format `cache-<index>`, and the index increments by one. The old cache is not deleted. You can manually delete these files from the runner storage.
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## Troubleshooting
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### Cache mismatch
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If you have a cache mismatch, follow these steps to troubleshoot.
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| Reason for a cache mismatch | How to fix it |
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| --------------------------- | ------------- |
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| You use multiple standalone runners (not in autoscale mode) attached to one project without a shared cache. | Use only one runner for your project or use multiple runners with distributed cache enabled. |
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| You use runners in autoscale mode without a distributed cache enabled. | Configure the autoscale runner to use a distributed cache. |
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| The machine the runner is installed on is low on disk space or, if you've set up distributed cache, the S3 bucket where the cache is stored doesn't have enough space. | Make sure you clear some space to allow new caches to be stored. There's no automatic way to do this. |
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| You use the same `key` for jobs where they cache different paths. | Use different cache keys to that the cache archive is stored to a different location and doesn't overwrite wrong caches. |
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#### Cache mismatch example 1
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If you have only one runner assigned to your project, the cache
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is stored on the runner's machine by default.
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If two jobs have the same cache key but a different path, the caches can be overwritten.
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For example:
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```yaml
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stages:
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- build
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- test
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job A:
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stage: build
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script: make build
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cache:
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key: same-key
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paths:
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- public/
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job B:
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stage: test
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script: make test
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cache:
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key: same-key
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paths:
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- vendor/
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```
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1. `job A` runs.
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1. `public/` is cached as cache.zip.
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1. `job B` runs.
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1. The previous cache, if any, is unzipped.
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1. `vendor/` is cached as cache.zip and overwrites the previous one.
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1. The next time `job A` runs it uses the cache of `job B` which is different
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and thus isn't effective.
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To fix this issue, use different `keys` for each job.
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#### Cache mismatch example 2
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In this example, you have more than one runner assigned to your
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project, and distributed cache is not enabled.
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The second time the pipeline runs, you want `job A` and `job B` to re-use their cache (which in this case
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is different):
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```yaml
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stages:
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- build
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- test
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job A:
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stage: build
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script: build
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cache:
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key: keyA
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paths:
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- vendor/
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job B:
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stage: test
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script: test
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cache:
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key: keyB
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paths:
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- vendor/
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```
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Even if the `key` is different, the cached files might get "cleaned" before each
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stage if the jobs run on different runners in subsequent pipelines.
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