Consider increasing the number of parallel jobs for container registry cleanup policies
Context
The cleanup policy for tags allows you programmatically maintain your project's container registry by choosing which container images to keep and which to remove. This allows you to reduce your storage usage and declutter the user interface.
GitLab has been working to improve the scalability of this feature so that it can be rolled out for all projects regardless of image repository size. Currently, projects created prior to milestone 12.8 will have the feature disabled.
Problem to solve
As we consider rolling out this feature for all GitLab.com historical projects, we need to consider scalability and performance. Although many of the scalability concerns are being addressed in #267546 (closed), the current feature limits the number of parallel jobs that can be run on GitLab.com to 2. Given that the GitLab.org project has many hundreds of thousands of tags, we will need to increase that number over time.
Why it's important
GitLab is seeking to deploy and migrate a new container registry. This new registry will support online garbage collection and a number of other features. However, migrating the data from one registry to another can be time consuming and computationally expensive. So, the more projects that have cleanup policies enabled, running and working, the less data that needs to be moved later in the year.
Proposal
Increase the number of parallel jobs available for cleanup policies from 2 to 3. Once complete, we can monitor activity and see if it makes sense to increase it from 3 to 4 and eventually 4 to 5.