Writing Tasks

Task defines where and how your scripts will be executed. Let's see a line-by-line example of a .cirrus.yml configuration file first:

test_task:
  container:
    image: gradle:jdk8
    cpu: 4
    memory: 10G
  test_script: gradle test

The example above defines a single task that will be scheduled and executed on the Community Cluster using the gradle:jdk8 Docker image. Only one user defined script instruction to run gradle test will be executed. Pretty simple, isn't it?

A task simply defines a compute service to schedule the task on and a sequence of script and cache instructions that will be executed.

Please read topics below if you want better understand what's doing on in a more complex .cirrus.yml configuration file such as this:

# global default
container:
  image: node:latest

lint_task:      
  node_modules_cache:
    folder: node_modules
    fingerprint_script: cat yarn.lock
    populate_script: yarn install

  test_script: yarn run lint

test_task:
  container:
    matrix:
      image: node:latest
      image: node:8.3.0

  node_modules_cache:
    folder: node_modules
    fingerprint_script: cat yarn.lock
    populate_script: yarn install

  test_script: yarn run test

publish_task:
  depends_on: 
    - test 
    - lint
  only_if: $BRANCH == "master"

  node_modules_cache:
    folder: node_modules
    fingerprint_script: cat yarn.lock
    populate_script: yarn install

  publish_script: yarn run publish

Task Naming

To name a task one can simply use the name field. foo_task syntax is simply a syntactic sugar. The following two task definitions are identical:

foo_task:
  ...

task:
  name: foo
  ...

Script Instruction¶

A script instruction executes commands via shell on Unix or batch on Windows. A script instruction can be named by adding a name as a prefix. For example test_script or my_very_specific_build_step_script. Naming script instructions helps gather more granular information about task execution. Cirrus CI will use it in future to auto-detect performance regressions.

Script commands can be specified as a single string value or a list of string values in a .cirrus.yml configuration file like in the example below:

check_task:
  compile_script: gradle --parallel classes testClasses
  check_script:
    - echo "Here comes more then one script!"
    - printenv
    - gradle check

Background Script Instruction¶

A background_script instruction is absolutely the same as script instruction but Cirrus CI won't wait for the script to finish and will continue execution of following instructions.

Background scripts can be useful when something needs to be executed in the background. For example, a database or some emulators. Traditionally the same effect is achieved by adding & to a command like $: command &. Problem here is that logs from command will be mixed into regular logs of the following commands. By using background scripts not only logs will be properly saved and displayed, but also command itself will be properly killed in the end of a task.

Here is an example of how background_script instruction can be used to run an android emulator:

android_test_task:
  start_emulator_background_script: emulator -avd test -no-audio -no-window
  wait_for_emulator_to_boot_script: adb wait-for-device
  test_script: gradle test

Cache Instruction¶

A cache instruction allows to persist a folder and reuse it during the next execution of the task. A cache instruction can be named the same way as script instruction.

Here is an example:

test_task:
  container:
    image: node:latest
  node_modules_cache:
    folder: node_modules
    fingerprint_script: cat yarn.lock
    populate_script: yarn install
  test_script: yarn run test

The folder is a required field that tells the agent which folder to cache. It should be relative to the working directory, or the root directory of the machine (ex. node_modules or /usr/bin/bundler).

A fingerprint_script is an optional field that can specify a script that will be executed and console output of which will be used as a key for the given cache. By default the task name is used as a fingerprint value.

populate_script is an optional field that can specify a script that will be executed to populate the cache. populate_script should create the folder if it doesn't exist before the cache instruction. If your dependencies are updated often, please pay attention to fingerprint_script and make sure it will produce different outputs for different versions of your dependency (ideally just print locked versions of dependencies).

That means the only difference between the example above and below is that yarn install will always be executed in the example below where in the example above only when yarn.lock has changes.

test_task:
  container:
    image: node:latest
  node_modules_cache:
    folder: node_modules
    fingerprint_script: cat yarn.lock
  install_script: yarn install
  test_script: yarn run test

Caching for Pull Requests

Tasks for PRs upload caches to a separate caching namespace to not interfere with caches used by other tasks. But such PR tasks can read all caches even from the main caching namespace for a repository.

Execution Behavior of Instructions¶

By default Cirrus CI executes instructions one after another and stops the overall task execution on the first failure. Sometimes there might be situations when some scripts should always be executed or some debug information needs to be saved on a failure. For such situations the always and on_failure keywords can be used to group instructions.

task:
  test_script: ./run_tests.sh
  on_failure:
    debug_script: ./print_additional_debug_info.sh
  always:
    test_reports_script: ./print_test_reports.sh

In the example above, print_additional_debug_info.sh script will be executed only on failures to output some additional debug information. print_test_reports.sh on the other hand will be executed both on successful and and failed runs to print test reports (test reports are always useful! ).

Environment Variables¶

Environment variables can be configured under the env or environment keywords in .cirrus.yml files. Here is an example:

echo_task:
  env:
    FOO: Bar
  echo_script: echo $FOO

Also some default environment variables are pre-defined:

Name	Value / Description
CI	true
CIRRUS_CI	true
CI_NODE_INDEX	Index of the current task within `CI_NODE_TOTAL` tasks
CI_NODE_TOTAL	Total amount of unique tasks for a given `CIRRUS_BUILD_ID` build
CONTINUOUS_INTEGRATION	true
CIRRUS_BASE_BRANCH	Base branch name if current build was triggered by a PR. For example `master`
CIRRUS_BASE_SHA	Base SHA if current build was triggered by a PR
CIRRUS_BRANCH	Branch name. For example `my-feature`
CIRRUS_BUILD_ID	Unique build ID
CIRRUS_CHANGE_IN_REPO	Git SHA
CIRRUS_CHANGE_MESSAGE	Commit message or PR title and description, depending on trigger event (Non-PRs or PRs respectively).
CIRRUS_DEFAULT_BRANCH	Default repository branch name. For example `master`
CIRRUS_LAST_GREEN_BUILD_ID	The build id of the last successful build on the same branch at the time of the current build creation.
CIRRUS_LAST_GREEN_CHANGE	Corresponding to `CIRRUS_LAST_GREEN_BUILD_ID` SHA (used in `changesInclude` function).
CIRRUS_PR	PR number if current build was triggered by a PR. For example `239`.
CIRRUS_TAG	Tag name if current build was triggered by a new tag. For example `v1.0`
CIRRUS_OS, OS	Host OS. Either `linux`, `windows` or `darwin`.
CIRRUS_TASK_NAME	Task name
CIRRUS_TASK_ID	Unique task ID
CIRRUS_RELEASE	GitHub Release id if current tag was created for a release. Handy for uploading release assets.
CIRRUS_REPO_CLONE_TOKEN	Temporary GitHub access token to perform a clone.
CIRRUS_REPO_NAME	Repository name. For example `my-project`
CIRRUS_REPO_OWNER	Repository owner (an organization or a user). For example `my-organization`
CIRRUS_REPO_FULL_NAME	Repository full name/slug. For example `my-organization/my-project`
CIRRUS_REPO_CLONE_URL	URL used for cloning. For example `https://github.com/my-organization/my-project.git`
CIRRUS_USER_COLLABORATOR	`true` if a user initialized a build is already a contributor to the repository. `false` otherwise.
CIRRUS_USER_PERMISSION	`admin`, `write`, `read` or `none`.
CIRRUS_HTTP_CACHE_HOST	Host and port number on which local HTTP cache can be accessed on.

Behavioral Environment Variables¶

And some environment variables can be set to control behavior of the Cirrus CI Agent:

Name	Default Value	Description
CIRRUS_CLONE_DEPTH	`0` which will reflect in a full clone of a single branch	Clone depth.
CIRRUS_SHELL	`sh` on Linux/macOS and `cmd.exe` on Windows	Shell that Cirrus CI uses to execute scripts. By default `sh` is used.
CIRRUS_WORKING_DIR	`cirrus-ci-build` folder inside of a system's temporary folder	Working directory where Cirrus CI executes builds. Default to `cirrus-ci-build` folder inside of a system's temporary folder.

Encrypted Variables¶

It is possible to securely add sensitive information to a .cirrus.yml file. Encrypted variables are only available to builds initialized or approved by users with write permission to a corresponding repository.

In order to encrypt a variable go to repository's settings page via clicking settings icon on a repository's main page (for example https://cirrus-ci.com/github/my-organization/my-repository) and follow instructions.

Warning

Only users with WRITE permissions can add encrypted variables to a repository.

An encrypted variable will be presented in a form like ENCRYPTED[qwerty239abc] which can be safely committed to .cirrus.yml file:

publish_task:
  environment:
    AUTH_TOKEN: ENCRYPTED[qwerty239abc]
  script: ./publish.sh

Cirrus CI encrypts variables with a unique per repository 256-bit encryption key so forks and even repositories within the same organization cannot re-use them. qwerty239abc from the example above is NOT the content of your encrypted variable, it's just an internal ID. No one can brute force your secrets from such ID. In addition, Cirrus CI doesn't know a relation between an encrypted variable and a repository for which the encrypted variable was created.

Matrix Modification¶

Sometimes it's useful to run the same task against different software versions. Or run different batches of tests based on an environment variable. For cases like these, the matrix modifier comes very handy. It's possible to use matrix keyword only inside of a particular task to have multiple tasks based on the original one. Each new task will be created from the original task by replacing the whole matrix YAML node with each matrix's children separately.

Let check an example of a .cirrus.yml:

test_task:
  container:
    matrix:
      image: node:latest
      image: node:8.3.0
  test_script: yarn run test

Which will be expanded into:

test_task:
  container:
    image: node:latest
  test_script: yarn run test

test_task:
  container:
    image: node:8.3.0
  test_script: yarn run test

Tip

The matrix modifier can be used multiple times within a task.

The matrix modification makes it easy to create some pretty complex testing scenarios like this:

test_task:
  container:
    matrix:
      image: node:latest
      image: node:8.3.0
  env:
    matrix:
      COMMAND: test
      COMMAND: lint
  node_modules_cache:
    folder: node_modules
    fingerprint_script:
      - node --version
      - cat yarn.lock
    populate_script: yarn install
  test_script: yarn run $COMMAND

Task Execution Dependencies¶

Sometimes it might be very handy to execute some tasks only after successful execution of other tasks. For such cases it is possible to specify task names that a particular task depends. Use depends_on keyword to define dependencies:

lint_task:
  script: yarn run lint

test_task:
  script: yarn run test

publish_task:
  depends_on: 
    - test
    - lint
  script: yarn run publish

Task Names

It is possible to specify task name via name field. lint_task syntax is simply a syntactic sugar that will be expanded into:

task:
  name: lint
  ...

Names can be also pretty complex:

task:
  name: test (linux)
  ...

task:
  name: test (windows)
  ...

task:
  name: test (macOS)
  ...

deploy_task:
  depends_on:
    - test (linux)
    - test (windows)
    - test (macOS)
  ...

Conditional Task Execution¶

Some tasks are meant to be created only if a certain condition is met. And some tasks can be skipped in some cases. Cirrus CI supports the only_if and skip keywords in order to provide such flexibility:

The only_if keyword controls whether or not a task will be created. For example, you may want to publish only changes committed to the master branch.
```
publish_task:
  only_if: $CIRRUS_BRANCH == 'master'
  script: yarn run publish
```
The skip keyword allows to skip execution of a task and mark it as successful. For example, you may want to skip linting if no source files have changed since the last successful run.
```
lint_task:
  skip: "!changesInclude('.cirrus.yml', '*.js', '**/*.js')"
  script: yarn run lint
```

Skip CI Completely

Simply include [skip ci] or [ci skip] in your commit message in order to skip CI execution for a commit completely.

If you push multiple commits at the same time, only the commit message of HEAD will be checked for [skip ci] or [ci skip].

Supported Operators¶

Currently only basic operators like ==, !=, =~, !=~, &&, || and unary ! are supported in only_if and skip expressions. Environment variables can also be used as usually.

Pattern Matching Example

Use =~ operator for pattern matching.

check_aggreement_task:
  only_if: $CIRRUS_BRANCH =~ 'pull/.*'

Supported Functions¶

Currently only one function is supported in the only_if and skip expressions. changesInclude function allows to check which files were changed. changesInclude behaves differently for PR builds and regular builds:

For PR builds, changesInclude will check the list of files affected by the PR.
For regular builds, changesInclude will use the CIRRUS_LAST_GREEN_CHANGE environment variable to determine list of affected files between CIRRUS_LAST_GREEN_CHANGE and CIRRUS_CHANGE_IN_REPO.

changesInclude function can be very useful for skipping some tasks when no changes to sources have been made since the last successful Cirrus CI build.

lint_task:
  skip: "!changesInclude('.cirrus.yml', '*.js', '**/*.js')"
  script: yarn run lint

Auto-Cancellation of Tasks¶

Cirrus CI can automatically cancel tasks in case of new pushes to the same branch. By default Cirrus CI auto-cancels all tasks for non default branch (for most repositories master branch) but this behavior can be changed by specifying auto_cancellation field:

task:
  auto_cancellation: $CIRRUS_BRANCH != 'master' && $CIRRUS_BRANCH !=~ 'release/.*'
  ...

Failure Toleration¶

Sometimes tasks can play a role of sanity checks. For example, a task can check that your library is working with the latest nightly version of some dependency package. It will be great to be notified about such failures but it's not necessary to fail the whole build when a failure occurs. Cirrus CI has the allow_failures keyword which will make a task to not affect the overall status of a build.

test_nightly_task:
  allow_failures: $SOME_PACKAGE_DEPENDENCY_VERSION == 'nightly'

Skipping Notifications

You can also skip posting red statuses to GitHub via skip_notifications field.

skip_notifications: $SOME_PACKAGE_DEPENDENCY_VERSION == 'nightly'

It can help to track potential issues overtime without distracting the main workflow.

HTTP Cache¶

For the most cases regular caching mechanism where Cirrus CI caches a folder is more than enough. But modern build systems like Gradle, Bazel and Pants can take advantage of remote caching. Remote caching is when a build system uploads and downloads intermediate results of a build execution while the build itself is still executing.

Cirrus CI agent starts a local caching server and exposes it via CIRRUS_HTTP_CACHE_HOST environments variable. Caching server supports GET, POST and HEAD requests to upload, download and check presence of artifacts.

Info

If port 12321 is available CIRRUS_HTTP_CACHE_HOST will be equal to localhost:12321.

For example running the following command:

curl -s -X POST --data-binary=@myfolder.tar.gz http://$CIRRUS_HTTP_CACHE_HOST/mykey

... has the same effect as a caching instruction of myfolder folder where sha1sum of all the myfolder contents is equal to mykey:

myfolder_cache:
  folder: myfolder

Info

To see how HTTP Cache can be used with Gradle's Build Cache please check this example.

Additional Containers¶

Sometimes one container is not enough to run a CI build. For example, your application might use a MySQL database as a storage. In this case you most likely want a MySQL instance running for your tests.

One option here is to pre-install MySQL and use a background_script to start it. This approach has some inconveniences like the need to pre-install MySQL by building a custom Docker container.

For such use cases Cirrus CI allows to run additional containers in parallel with the main container that executes a task. Each additional container is defined under additional_containers keyword in .cirrus.yml. Each additional container should have a unique name and specify at least Docker image and port that this container exposes.

In the example below we use an official MySQL Docker image that exposes the standard MySQL port (3306). Tests will be able to access MySQL instance via localhost:3306.

container:
  image: golang:1.9.4
  additional_containers:
    - name: mysql
      image: mysql:8
      port: 3306
      cpu: 1.0
      memory: 512Mi
      env:
        MYSQL_ROOT_PASSWORD: ""

Additional container can be very handy in many scenarios. Please check Cirrus CI catalog of examples for more details.

Default Resources

By default, each additional container will get 0.5 CPU and 512Mi of memory. These values can be configured as usual via cpu and memory fields.

Warning

Note that additional_containers can be used only with Community Cluster or Google's Kubernetes Engine.

Embedded Badges¶

Cirrus CI provides a way to embed a badge that can represent status of your builds into a ReadMe file or a website.

For example, this is a badge for cirruslabs/cirrus-ci-web repository that contains Cirrus CI's front end:

In order to embed such a check into your ReadMe file or your website, simply use a URL to a badge that looks like this:

https://api.cirrus-ci.com/github/<USER OR ORGANIZATION>/<REPOSITORY>.svg

If you want a badge for a particular branch, simply use ?branch=<BRANCH NAME> query parameter (at the end of the URL) like this:

https://api.cirrus-ci.com/github/<USER OR ORGANIZATION>/<REPOSITORY>.svg?branch=<BRANCH NAME>

If you want a badge for a particular task within the latest finished build, simply use ?task=<TASK NAME> query parameter (at the end of the URL) like this:

https://api.cirrus-ci.com/github/<USER OR ORGANIZATION>/<REPOSITORY>.svg?task=tests

You can even pick a specific script instruction within the task with an additional script=<SCRIPT NAME> parameter:

https://api.cirrus-ci.com/github/<USER OR ORGANIZATION>/<REPOSITORY>.svg?task=build&script=lint

Badges in Markdown¶

Here is how Cirrus CI's badge can be embeded in a Markdown file:

[![Build Status](https://api.cirrus-ci.com/github/<USER OR ORGANIZATION>/<REPOSITORY>.svg)](https://cirrus-ci.com/github/<USER OR ORGANIZATION>/<REPOSITORY>)

Custom Clone Command¶

By default Cirrus CI uses a Git client implemented purely in Go to perform a clone of a single branch with full Git history. It is possible to control clone depth via CIRRUS_CLONE_DEPTH environment variable.

Customizing clone behavior is a simple as overriding clone_script. For example, here an override to use a pre-installed Git client (if your build environment has it) to do a shallow clone of a single branch:

task:
  clone_script: |
    if [[ -z "$CIRRUS_PR" ]]; then
      git clone --recursive --branch=$CIRRUS_BRANCH https://x-access-token:${CIRRUS_REPO_CLONE_TOKEN}@github.com/${CIRRUS_REPO_FULL_NAME}.git $CIRRUS_WORKING_DIR
      git reset --hard $CIRRUS_CHANGE_IN_REPO
    else
      git clone --recursive https://x-access-token:${CIRRUS_REPO_CLONE_TOKEN}@github.com/${CIRRUS_REPO_FULL_NAME}.git $CIRRUS_WORKING_DIR
      git fetch origin pull/$CIRRUS_PR/head:pull/$CIRRUS_PR
      git reset --hard $CIRRUS_CHANGE_IN_REPO
    fi
  ...

go-git benefits

Using go-git made it possible to not require a pre-installed Git from an execution environment. For example, most of alpine-based containers doesn't have Git pre-installed. Because of go-git you can even use distroless containers with Cirrus CI which don't even have Operation System.