Make jobs start earlier with needs
You can use the needs keyword to create dependencies between jobs
in a pipeline. Jobs run as soon as their dependencies are met, regardless of the pipeline’s stages
configuration. You can even configure a pipeline with no stages defined (effectively one large stage)
and jobs still run in the proper order. This pipeline structure is a kind of
directed acyclic graph.
For example, you may have a specific tool or separate website that is built
as part of your main project. Using needs, you can specify dependencies between
these jobs and GitLab executes the jobs as soon as possible instead of waiting
for each stage to complete.
Unlike other solutions for CI/CD, GitLab does not require you to choose between staged
or stageless execution flow. You can implement a hybrid combination of staged and stageless
in a single pipeline, using only the needs keyword to enable the feature for any job.
Consider a monorepo as follows:
./service_a
./service_b
./service_c
./service_d
This project could have a pipeline organized into three stages:
| build | test | deploy |
|---|---|---|
build_a
| test_a
| deploy_a
|
build_b
| test_b
| deploy_b
|
build_c
| test_c
| deploy_c
|
build_d
| test_d
| deploy_d
|
You can improve job execution by using needs to relate the a jobs to each other
separately from the b, c, and d jobs. build_a could take a very long time to build,
but test_b doesn’t need to wait, it can be configured to start as soon as build_b is finished,
which could be much faster.
If desired, c and d jobs can be left to run in stage sequence.
The needs keyword also works with the parallel keyword,
giving you powerful options for parallelization in your pipeline.
Use cases
You can use the needs keyword to define several different kinds of
dependencies between jobs in a CI/CD pipeline. You can set dependencies to fan in or out,
and even merge back together (diamond dependencies). These dependencies could be used for
pipelines that:
- Handle multi-platform builds.
- Have a complex web of dependencies like an operating system build.
- Have a deployment graph of independently deployable but related microservices.
Additionally, needs can help improve the overall speed of pipelines and provide fast feedback.
By creating dependencies that don’t unnecessarily
block each other, your pipelines run as quickly as possible regardless of
pipeline stages, ensuring output (including errors) is available to developers
as quickly as possible.
Needs dependency visualization (deprecated)
needs relationships in the
full pipeline graph instead.The needs dependency visualization makes it easier to visualize the dependencies between jobs in a pipeline. This graph displays all the jobs in a pipeline that need or are needed by other jobs. Jobs with no dependencies are not displayed in this view.
To see the needs visualization, select Needs when viewing a pipeline that uses the needs keyword.
Selecting a node highlights all the job paths it depends on.
