# Triggering Builds through the API > [Introduced][ci-229] in GitLab CE 7.14. > **Note**: GitLab 8.12 has a completely redesigned build permissions system. Read all about the [new model and its implications](../../user/project/new_ci_build_permissions_model.md#build-triggers). Triggers can be used to force a rebuild of a specific branch, tag or commit, with an API call. ## Add a trigger You can add a new trigger by going to your project's **Settings > Triggers**. The **Add trigger** button will create a new token which you can then use to trigger a rebuild of this particular project. 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) ## 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 build To trigger a build you need to send a `POST` request to GitLab's API endpoint: ``` POST /projects/:id/trigger/builds ``` The required parameters are the trigger's `token` and the Git `ref` on which the trigger will be performed. Valid refs are the branch, the tag or the commit SHA. The `:id` of a project can be found by [querying the API](../../api/projects.md) or by visiting the **Triggers** page which provides self-explanatory examples. When a rebuild is triggered, the information is exposed in GitLab's UI under the **Builds** page and the builds are marked as `triggered`. ![Marked rebuilds as triggered on builds page](img/builds_page.png) --- You can see which trigger caused the rebuild by visiting the single build page. The token of the trigger is exposed in the UI as you can see from the image below. ![Marked rebuilds as triggered on a single build page](img/trigger_single_build.png) --- See the [Examples](#examples) section for more details on how to actually trigger a rebuild. ## Trigger a build from webhook > Introduced in GitLab 8.14. To trigger a build from webhook of another project you need to add the following webhook url for Push and Tag push events: ``` https://gitlab.example.com/api/v3/projects/:id/ref/:ref/trigger/builds?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 build 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. ![Build 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/v3/projects/9/trigger/builds ``` 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/v3/projects/9/trigger/builds?token=TOKEN&ref=master" ``` ### Triggering a build 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/v3/projects/9/trigger/builds" only: - tags ``` Now, whenever a new tag is pushed on project A, the build 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/v3/projects/9/trigger/builds ``` ### Using webhook to trigger builds You can add the following webhook to another project in order to trigger a build: ``` https://gitlab.example.com/api/v3/projects/9/ref/master/trigger/builds?token=TOKEN&variables[UPLOAD_TO_S3]=true ``` ### Using cron to trigger nightly builds Whether you craft a script or just run cURL directly, you can trigger builds in conjunction with cron. The example below triggers a build on the `master` branch of project with ID `9` every night at `00:30`: ```bash 30 0 * * * curl --request POST --form token=TOKEN --form ref=master https://gitlab.example.com/api/v3/projects/9/trigger/builds ``` [ci-229]: https://gitlab.com/gitlab-org/gitlab-ci/merge_requests/229