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Chapter 9. Namespace auto-pruning architecture

Red Hat Quay namespace auto-pruning uses database tables for policies and task status and an auto-prune worker that runs configured policies. You can use this overview to understand how policies are stored and executed.

For the namespace auto-pruning feature, two distinct database tables within a database schema were created: one for namespaceautoprunepolicy and another for autoprunetaskstatus. An auto-prune worker carries out the configured policies.

9.1. Namespace auto prune policy database table
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The namespaceautoprunepolicy database table holds the policy configuration for a single namespace. There is only one entry per namespace, but there is support for multiple rows per namespace_id. The policy field holds the policy details, such as {method: "creation_date", olderThan: "2w"} or {method: "number_of_tags", numTags: 100}.

Table 9.1. namespaceautoprunepolicy database table
FieldTypeAttributesDescription

uuid

character varying (225)

Unique, indexed

Unique identifier for this policy

namespace_id

Integer

Foreign Key

Namespace that the policy falls under

policy

text

JSON

Policy configuration

9.2. Auto-prune task status database table
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The autoprunetaskstatus table registers tasks to be executed by the auto-prune worker. Tasks are executed within the context of a single namespace. Only one task per namespace exists.

Table 9.2. autoprunetaskstatus database table
FieldTypeAttributesDescription

namespace_id

Integer

Foreign Key

Namespace that this task belongs to

last_ran_ms

Big Integer (bigint)

Nullable, indexed

Last time that the worker executed the policies for this namespace

status

text

Nullable

Details from the last execution task

9.3. Auto-prune worker
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The following sections detail information about the auto-prune worker.

Auto-prune task creation
When a new policy is created in the namespaceautoprunepolicy database table, a row is also created in the autoprunetask table. This is done in the same transaction. The auto-prune worker uses the entry in the autoprunetask table to identify which namespace it should execute policies for.
Auto-prune worker execution
The auto-pruning worker is an asynchronous job that executes configured policies. Its workflow is based on values in the autoprunetask table. When a task begins, the following occurs:

The auto-pruning worker is an asynchronous job that executes configured policies. Its workflow is based on values in the autoprunetask table. When a task begins, the following occurs:

  • The auto-prune worker starts on a set interval, which defaults at 30 seconds.

  • The auto-prune worker selects a row from autoprunetask with the least, or null, last_ran_ms and FOR UPDATE SKIP LOCKED.

    • A null last_ran_ms indicates that the task was never ran.
    • A task that has not run for the longest amount of time, or has never been run at all, is prioritized.

  • The auto-prune worker obtains the policy configuration from the namespaceautoprunepolicy table.

    • If no policy configuration exists, the entry from autoprunetask is deleted for this namespace and the procedure stops immediately.

  • The auto-prune worker begins a paginated loop of all repositories under the organization.

    • The auto-prune worker determines much pruning method to use based on policy.method.

  • The auto-prune worker executes the pruning method with the policy configuration retrieved earlier.

    • For pruning by the number of tags: the auto-pruner worker gets the number of currently active tags sorted by creation date, and deletes the older tags to the configured number.
    • For pruning by date: the auto-pruner worker gets the active tags older than the specified time span and any tags returned are deleted.
  • The auto-prune worker adds audit logs of the tags deleted.
  • The last_ran_ms gets updated after a row from autoprunetask is selected.
  • The auto-prune worker ends.
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