Chapter 19. Red Hat Quay garbage collection

Currently, all garbage collection happens discreetly, and there are no commands to manually run garbage collection. Red Hat Quay provides metrics that track the status of the different garbage collection workers.

For namespace and repository garbage collection, the progress is tracked based on the size of their respective queues. Namespace and repository garbage collection workers require a global lock to work. As a result, and for performance reasons, only one worker runs at a time.

Garbage collecting tagged images works differently than garbage collection on namespaces or repositories. Rather than having a queue of items to work with, the garbage collection workers for tagged images actively search for a repository with inactive or expired tags to clean up. Each instance of garbage collection workers will grab a repository lock, which results in one worker per repository.

For each type of garbage collection, Red Hat Quay provides metrics for the number of rows per table deleted by each garbage collection worker. The following image shows an example of how Red Hat Quay monitors garbage collection with the same metrics:

The following configuration fields are available to customize what is garbage collected, and the frequency at which garbage collection occurs:

The garbage collection features for image tags, namespaces, and repositories are stored in the config.yaml file. These features default to true.

In rare cases, you might want to disable garbage collection, for example, to control when garbage collection is performed. You can disable garbage collection by setting the GARBAGE_COLLECTION features to false. When disabled, dangling or untagged images, repositories, namespaces, layers, and manifests are not removed. This might increase the downtime of your environment.

Red Hat Quay introduced quota management in 3.7. With quota management, users have the ability to report storage consumption and to contain registry growth by establishing configured storage quota limits.

As of Red Hat Quay 3.7, garbage collection reclaims memory that was allocated to images, repositories, and blobs after deletion. Because the garbage collection feature reclaims memory after deletion, there is a discrepancy between what is stored in an environment’s disk space and what quota management is reporting as the total consumption. There is currently no workaround for this issue.

Use the following procedure to check your Red Hat Quay logs to ensure that garbage collection is working.

The following metrics show how many resources have been removed by garbage collection. These metrics show how many times the garbage collection workers have run and how many namespaces, repositories, and blobs were removed.

# TYPE quay_gc_iterations_created gauge
quay_gc_iterations_created{host="example-registry-quay-app-6df87f7b66-9tfn6",instance="",job="quay",pid="208",process_name="secscan:application"} 1.6317823190189714e+09
...

# HELP quay_gc_iterations_total number of iterations by the GCWorker
# TYPE quay_gc_iterations_total counter
quay_gc_iterations_total{host="example-registry-quay-app-6df87f7b66-9tfn6",instance="",job="quay",pid="208",process_name="secscan:application"} 0
...

# TYPE quay_gc_namespaces_purged_created gauge
quay_gc_namespaces_purged_created{host="example-registry-quay-app-6df87f7b66-9tfn6",instance="",job="quay",pid="208",process_name="secscan:application"} 1.6317823190189433e+09
...

# HELP quay_gc_namespaces_purged_total number of namespaces purged by the NamespaceGCWorker
# TYPE quay_gc_namespaces_purged_total counter
quay_gc_namespaces_purged_total{host="example-registry-quay-app-6df87f7b66-9tfn6",instance="",job="quay",pid="208",process_name="secscan:application"} 0
....

# TYPE quay_gc_repos_purged_created gauge
quay_gc_repos_purged_created{host="example-registry-quay-app-6df87f7b66-9tfn6",instance="",job="quay",pid="208",process_name="secscan:application"} 1.631782319018925e+09
...

# HELP quay_gc_repos_purged_total number of repositories purged by the RepositoryGCWorker or NamespaceGCWorker
# TYPE quay_gc_repos_purged_total counter
quay_gc_repos_purged_total{host="example-registry-quay-app-6df87f7b66-9tfn6",instance="",job="quay",pid="208",process_name="secscan:application"} 0
...

# TYPE quay_gc_storage_blobs_deleted_created gauge
quay_gc_storage_blobs_deleted_created{host="example-registry-quay-app-6df87f7b66-9tfn6",instance="",job="quay",pid="208",process_name="secscan:application"} 1.6317823190189059e+09
...

# HELP quay_gc_storage_blobs_deleted_total number of storage blobs deleted
# TYPE quay_gc_storage_blobs_deleted_total counter
quay_gc_storage_blobs_deleted_total{host="example-registry-quay-app-6df87f7b66-9tfn6",instance="",job="quay",pid="208",process_name="secscan:application"} 0
...