gitlab-org--gitlab-foss/doc/ci/triggers/README.md

# Triggering jobs through the API

> **Note**:
- [Introduced][ci-229] in GitLab CE 7.14.
- GitLab 8.12 has a completely redesigned job permissions system. Read all
  about the [new model and its implications](../../user/project/new_ci_build_permissions_model.md#job-triggers).
- GitLab 9.0 introduced a trigger ownership to solve permission problems.

Triggers can be used to force a rebuild of a specific `ref` (branch or tag)
with an API call.

## Add a trigger

You can add a new trigger by going to your project's
**Settings ➔ CI/CD Pipelines ➔ Triggers**. The **Add trigger** button will
create a new token which you can then use to trigger a rerun of this
particular project's pipeline.

Every new trigger you create, gets assigned a different token which you can
then use inside your scripts or `.gitlab-ci.yml`. You also have a nice
overview of the time the triggers were last used.

![Triggers page overview](img/triggers_page.png)

## Take ownership

Each created trigger when run will impersonate their associated user including
their access to projects and their project permissions.

You can take ownership of existing triggers by clicking *Take ownership*.
From now on the trigger will be run as you.

## Legacy triggers

Old triggers, created before 9.0 will be marked as Legacy. Triggers with
the legacy label do not have an associated user and only have access
to the current project.

Legacy trigger are considered deprecated and will be removed
with one of the future versions of GitLab.

## Revoke a trigger

You can revoke a trigger any time by going at your project's
**Settings > Triggers** and hitting the **Revoke** button. The action is
irreversible.

## Trigger a pipeline

> **Note**:
Valid refs are only the branches and tags. If you pass a commit SHA as a ref,
it will not trigger a job.

To trigger a job you need to send a `POST` request to GitLab's API endpoint:

```
POST /projects/:id/trigger/pipeline
```

The required parameters are the trigger's `token` and the Git `ref` on which
the trigger will be performed. Valid refs are the branch and the tag. The `:id`
of a project can be found by [querying the API](../../api/projects.md)
or by visiting the **CI/CD Pipelines** settings page which provides
self-explanatory examples.

When a rerun of a pipeline is triggered, the information is exposed in GitLab's
UI under the **Jobs** page and the jobs are marked as triggered 'by API'.

![Marked rebuilds as  on jobs page](img/builds_page.png)

---

You can see which trigger caused the rebuild by visiting the single job page.
A part of the trigger's token is exposed in the UI as you can see from the image
below.

![Marked rebuilds as triggered on a single job page](img/trigger_single_build.png)

---

See the [Examples](#examples) section for more details on how to actually
trigger a rebuild.

## Trigger a pipeline from webhook

> Introduced in GitLab 8.14.

To trigger a job from webhook of another project you need to add the following
webhook url for Push and Tag push events:

```
https://gitlab.example.com/api/v4/projects/:id/ref/:ref/trigger/pipeline?token=TOKEN
```

> **Note**:
- `ref` should be passed as part of url in order to take precedence over `ref`
  from webhook body that designates the branchref that fired the trigger in the source repository.
- `ref` should be url encoded if contains slashes.

## Pass job variables to a trigger

You can pass any number of arbitrary variables in the trigger API call and they
will be available in GitLab CI so that they can be used in your `.gitlab-ci.yml`
file. The parameter is of the form:

```
variables[key]=value
```

This information is also exposed in the UI.

![Job variables in UI](img/trigger_variables.png)

---

See the [Examples](#examples) section below for more details.

## Examples

Using cURL you can trigger a rebuild with minimal effort, for example:

```bash
curl --request POST \
     --form token=TOKEN \
     --form ref=master \
     https://gitlab.example.com/api/v4/projects/9/trigger/pipeline
```

In this case, the project with ID `9` will get rebuilt on `master` branch.

Alternatively, you can pass the `token` and `ref` arguments in the query string:

```bash
curl --request POST \
    "https://gitlab.example.com/api/v4/projects/9/trigger/pipeline?token=TOKEN&ref=master"
```

### Triggering a pipeline within `.gitlab-ci.yml`

You can also benefit by using triggers in your `.gitlab-ci.yml`. Let's say that
you have two projects, A and B, and you want to trigger a rebuild on the `master`
branch of project B whenever a tag on project A is created. This is the job you
need to add in project's A `.gitlab-ci.yml`:

```yaml
build_docs:
  stage: deploy
  script:
  - "curl --request POST --form token=TOKEN --form ref=master https://gitlab.example.com/api/v4/projects/9/trigger/pipeline"
  only:
  - tags
```

Now, whenever a new tag is pushed on project A, the job will run and the
`build_docs` job will be executed, triggering a rebuild of project B. The
`stage: deploy` ensures that this job will run only after all jobs with
`stage: test` complete successfully.

_**Note:** If your project is public, passing the token in plain text is
probably not the wisest idea, so you might want to use a
[secure variable](../variables/README.md#user-defined-variables-secure-variables)
for that purpose._

### Making use of trigger variables

Using trigger variables can be proven useful for a variety of reasons.

* Identifiable jobs. Since the variable is exposed in the UI you can know
  why the rebuild was triggered if you pass a variable that explains the
  purpose.
* Conditional job processing. You can have conditional jobs that run whenever
  a certain variable is present.

Consider the following `.gitlab-ci.yml` where we set three
[stages](../yaml/README.md#stages) and the `upload_package` job is run only
when all jobs from the test and build stages pass. When the `UPLOAD_TO_S3`
variable is non-zero, `make upload` is run.

```yaml
stages:
- test
- build
- package

run_tests:
  script:
  - make test

build_package:
  stage: build
  script:
  - make build

upload_package:
  stage: package
  script:
  - if [ -n "${UPLOAD_TO_S3}" ]; then make upload; fi
```

You can then trigger a rebuild while you pass the `UPLOAD_TO_S3` variable
and the script of the `upload_package` job will run:

```bash
curl --request POST \
  --form token=TOKEN \
  --form ref=master \
  --form "variables[UPLOAD_TO_S3]=true" \
  https://gitlab.example.com/api/v4/projects/9/trigger/pipeline
```

### Using webhook to trigger job

You can add the following webhook to another project in order to trigger a job:

```
https://gitlab.example.com/api/v4/projects/9/ref/master/trigger/pipeline?token=TOKEN&variables[UPLOAD_TO_S3]=true
```

[ci-229]: https://gitlab.com/gitlab-org/gitlab-ci/merge_requests/229