Projects that interact with each other should share a
queue. This is especially used in a dependent <pipeline.manager.dependent> pipeline. The project.queue can optionally refer to a specific queue object that can further configure the behavior of the queue.
Here is an example
The attributes available on a queue are as follows (all are optional unless otherwise specified):
This is used later in the project definition to refer to this queue.
Queues by default define a single queue for all projects and branches that use it. This is especially important if projects want to do upgrade tests between different branches in the gate. If a set of projects doesn't have this use case it can configure the queue to create a shared queue per branch for all projects. This can be useful for large projects to improve the throughput of a gate pipeline as this results in shorter queues and thus less impact when a job fails in the gate. Note that this means that all projects that should be gated must have aligned branch names when using per branch queues. Otherwise changes that belong together end up in different queues.
Define if Zuul is allowed to process circular dependencies between changes for this queue. All projects that are part of a dependency cycle must share the same change queue.
In case Zuul detects a dependency cycle it will make sure that every change also includes all other changes that are part of the cycle. However each change will still be a normal item in the queue with its own jobs.
Reporting of success will be postponed until all items in the cycle succeeded. In case of a failure in any of those items the whole cycle will be dequeued.
An error message will be posted to all items of the cycle in case some items fail to report (e.g. merge failure when some items were already merged). In this case the target branch(es) might be in a broken state.
In general, circular dependencies are considered to be an antipattern but can't be avoided in certain cases.