For a brief overview of how Prow runs jobs take a look at “Life of a Prow Job”.

For a brief cookbook for jobs intended for, please refer to config/jobs/

Make sure Prow has been deployed correctly:

  • The horologium component schedules periodic jobs.
  • The hook component schedules presubmit and postsubmit jobs, ensuring the repo:
    • enabled trigger in plugins.yaml
    • sends GitHub webhooks to prow.
  • The plank component schedules the pod requested by a prowjob.
  • The crier component reports status back to github.

How to configure new jobs

To configure a new job you’ll need to add an entry into config.yaml. If you have update-config plugin deployed then the config will be automatically updated once the PR is merged, else you will need to run make update-config. This does not require redeploying any binaries, and will take effect within a few minutes.

Alternatively, the inrepoconfig feature can be used to version Presubmit jobs in the same repository that also contains the code and have Prow load them dynamically. See its documentation for more details.

Prow requires you to have a basic understanding of kubernetes, such that you can define pods in yaml. Please see kubernetes documentation for help here, for example the Pod overview and PodSpec api reference.

Periodic config looks like so (see GoDocs for complete config):

- name: foo-job         # Names need not be unique, but must match the regex ^[A-Za-z0-9-._]+$
  decorate: true        # Enable Pod Utility decoration. (see below)
  interval: 1h          # Anything that can be parsed by time.ParseDuration.
  # Alternatively use a cron instead of an interval, for example:
  # cron: "05 15 * * 1-5"  # Run at 7:05 PST (15:05 UTC) every M-F
  extra_refs:            # Periodic job doesn't clone any repo by default, needs to be added explicitly
  - org: org
    repo: repo
    base_ref: main
  spec: {}              # Valid Kubernetes PodSpec.

Postsubmit config looks like so (see GoDocs for complete config):

  - name: bar-job         # As for periodics.
    decorate: true        # As for periodics.
    spec: {}              # As for periodics.
    max_concurrency: 10   # Run no more than this number concurrently.
    branches:             # Regexps, only run against these branches.
    - ^main$
    skip_branches:        # Regexps, do not run against these branches.
    - ^release-.*$

Postsubmits are run by the trigger plugin when a push event happens on a repo, hence they are configured per-repo. If no branches are specified, then they will run on every push to every branch on the given repo.

Postsubmit jobs apply run_if_changed and skip_if_only_changed filters based on which files were modified by the commits included in the specific push event from github.

Presubmit config looks like so (see GoDocs for complete config):

  - name: qux-job            # As for periodics.
    decorate: true           # As for periodics.
    always_run: true         # Run for every PR, or only when requested.
    run_if_changed: "qux/.*" # Regexp, only run on certain changed files.
    skip_report: true        # Whether to skip setting a status on GitHub.
    context: qux-job         # Status context. Defaults to the job name.
    max_concurrency: 10      # As for postsubmits.
    spec: {}                 # As for periodics.
    branches: []             # As for postsubmits.
    skip_branches: []        # As for postsubmits.
    trigger: "(?m)qux test this( please)?" # Regexp, see discussion.
    rerun_command: "qux test this please"  # String, see discussion.

Presubmit jobs are run for pull requests by the trigger plugin.

The trigger is a regexp that matches the rerun_command. Users will be told to input the rerun_command when they want to rerun the job. Actually, anything that matches trigger will suffice. This is useful if you want to make one command that reruns all jobs. If unspecified, the default configuration makes /test <job-name> trigger the job.

See the Triggering Jobs section below to learn how to control when jobs are automatically run. We also have sections about posting and requiring GitHub status contexts. A useful pattern when adding new jobs is to start with always_run set to false and skip_report set to true. Test it out a few times by manually triggering, then switch always_run to true. Watch for a couple days, then switch skip_report to false.

Presubmit jobs apply run_if_changed and skip_if_only_changed filters based on which files were modified in any of the commits in the pull request.


Presets can be used to define commonly reused values for a subset of fields for PodSpecs and BuildSpecs. A preset config looks like:

- labels:                  # a job with these labels/values will have the preset applied
    preset-foo-bar: "true" #   key:value pair must be unique among presets
  env:                     # list of valid Kubernetes EnvVars
  - name: FOO
    value: BAR
  volumes:                 # list of valid Kubernetes Volumes
  - name: foo
    emptyDir: {}
  - name: bar
      secretName: bar
  volumeMounts:            # list of valid Kubernetes VolumeMounts
  - name: foo
    mountPath: /etc/foo
  - name: bar
    mountPath: /etc/bar
    readOnly: true

And to use the preset, add corresponding label in prow job definition like:

- name: obfsucated-job-with-mysteriously-hidden-side-effects
    preset-foo-bar: "true"

Alternatively, anonymous presets can be applied to all jobs, the config looks like:

- env:                     # a preset with no labels is applied to all jobs
  - name: BAZ
    value: qux
    # etc...
    # etc...

Standard Triggering and Execution Behavior for Jobs

When configuring jobs, it is necessary to keep in mind the set of rules Prow has for triggering jobs, the GitHub status contexts that those jobs provide, and the rules for protecting those contexts on branches.

Triggering Jobs

Trigger Types

prow will consider three different types of jobs that run on pull requests (presubmits):

  1. jobs that run unconditionally and automatically. All jobs that set always_run: true fall into this set.
  2. jobs that run conditionally, but automatically. All jobs that set run_if_changed or skip_if_only_changed to some value fall into this set.
  3. jobs that run conditionally, but not automatically. All jobs that set always_run: false and do not set run_if_changed/skip_if_only_changed to any value fall into this set and require a human to trigger them with a command.

By default, jobs fall into the third category and must have their always_run, run_if_changed, or skip_if_only_changed configured to operate differently.

In the rest of this document, “a job running unconditionally” indicates that the job will run even if it is normally conditional and the conditions are not met. Similarly, “a job running conditionally” indicates that the job runs if all of its conditions are met.

Triggering Jobs Based On Changes

Jobs that set always_run: false may be configured to run conditionally based on the contents of the pull request. run_if_changed and skip_if_only_changed accept a (Golang-style) regular expression which is run against the path of each changed file.

run_if_changed triggers the job if any path matches. For example, you may wish to trigger a compilation job if the pull request changes any *.c or *.h file, or the Makefile:

  - name: compile-job
    always_run: false
    run_if_changed: "(\\.[ch]|^Makefile)$"

skip_if_only_changed skips the job if all paths match. For example, you may wish to skip a compilation job for pull requests that only change documentation files:

  - name: compile-job
    always_run: false
    skip_if_only_changed: "^docs/|\\.(md|adoc)$|^(README|LICENSE)$"

Both of the above examples would trigger on a pull request containing foo/bar.c and, but not one containing only


  • run_if_changed and skip_if_only_changed are mutually exclusive.
  • Jobs which would otherwise be skipped based on this configuration can still be triggered explicitly with comments (see below).
  • Only presubmit and postsubmit jobs are inherently associated with git refs and can use these fields.

Triggering Jobs With Comments

A developer may trigger presubmits by posting a comment to a pull request that contains one or more of the following phrases:

  • /test job-name : When posting /test job-name, any jobs with matching triggers will be triggered unconditionally.
  • /retest : When posting /retest, two types of jobs will be triggered:
    • all jobs that have run and failed will run unconditionally
    • any not-yet-executed automatically run jobs will run conditionally
  • /test all : When posting /test all, all automatically run jobs will run conditionally.

Note: It is possible to configure a job’s trigger to match any of the above keywords (/retest and/or /test all) but this behavior is not suggested as it will confuse developers that expect consistent behavior from these commands. More generally, it is possible to configure a job’s trigger to match any command that is otherwise known to Prow in some other context, like /close. It is similarly not suggested to do this.

Posting GitHub Status Contexts

Presubmit and postsubmit jobs post a status context to the GitHub commit under test once they start, unless the job is configured with skip_report: true.

Use a /retest or /test job-name to re-trigger the test and hopefully update the failed context to passing.

If a job should no longer trigger on the pull request, use the /skip command to dismiss a failing status context (depends on skip plugin).

Repo administrators can also /override job-name in case of emergency (depends on the override plugin).

Requiring Job Statuses

Requiring Jobs for Auto-Merge Through Tide

Tide will treat jobs in the following manner for merging:

  • unconditionally run jobs with required status contexts are always required to have passed on a pull request to merge
  • conditionally run jobs with required status contexts are required to have passed on a pull request to merge if the job currently matches the pull request.
  • jobs with optional status contexts are ignored when merging

In order to set a job’s context to be optional, set optional: true on the job. If it is required to not post the results of the job to GitHub whatsoever, the job may be set to be optional and silent by setting skip_report: true. It is valid to set both of these options at the same time.

Protecting Status Contexts

The branch protection rules will only enforce the presence of jobs that run unconditionally and have required status contexts. As conditionally-run jobs may or may not post a status context to GitHub, they cannot be required through this mechanism.

Running a ProwJob in a Build Cluster

ProwJobs that execute as Kubernetes resources (namely agent: kubernetes jobs that run as Pods, the default value) can specify a cluster: build-cluster-name field as part of the ProwJob config to specify that the job should be run in a build cluster other than the default build cluster.

- name: periodic-cluster-a
  cluster: cluster-a
  - name: presubmit-cluster-b
    cluster: cluster-b
  - name: postsubmit-default-cluster
    # cluster field omitted or set to "default"

You can learn more about creating and using build clusters in “Using Prow at Scale” and “Deploying Prow”.

Pod Utilities

If you are adding a new job that will execute on a Kubernetes cluster (agent: kubernetes, the default value) you should consider using the Pod Utilities. The pod utils decorate jobs with additional containers that transparently provide source code checkout and log/metadata/artifact uploading to GCS.

Job Environment Variables

Prow will expose the following environment variables to your job. If the job runs on Kubernetes, the variables will be injected into every container in your pod, If the job is run in Jenkins, Prow will supply them as parameters to the build.

Variable Periodic Postsubmit Batch Presubmit Description Example
CI Represents whether the current environment is a CI environment true
ARTIFACTS Directory in which to place files to be uploaded when the job completes /logs/artifacts
JOB_NAME Name of the job. pull-test-infra-bazel
JOB_TYPE Type of job. presubmit
JOB_SPEC JSON-encoded job specification. see below
BUILD_ID Unique build number for each run. 12345
PROW_JOB_ID Unique identifier for the owning Prow Job. 1ce07fa2-0831-11e8-b07e-0a58ac101036
REPO_OWNER GitHub org that triggered the job. kubernetes
REPO_NAME GitHub repo that triggered the job. test-infra
PULL_BASE_REF Ref name of the base branch. master
PULL_BASE_SHA Git SHA of the base branch. 123abc
PULL_REFS All refs to test. master:123abc,5:qwe456
PULL_NUMBER Pull request number. 5
PULL_PULL_SHA Pull request head SHA. qwe456
PULL_HEAD_REF Pull request branch name. fixup-some-stuff
PULL_TITLE Pull request title. Add something

Examples of the JSON-encoded job specification follow for the different job types:

Periodic Job:


Postsubmit Job:


Presubmit Job:


Batch Job:


Testing a new job

See “How to test a ProwJob”.


Prow can display badges that signal whether jobs are passing (example).

The format to send your deck URL is /badge.svg?jobs=single-job-name or /badge.svg?jobs=common-job-prefix-*.