[IGNITE-22467] PlacementDriver should have a method to return an assignments for a specified partition

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.0
• Labels: ignite-3
• Epic Link: Read from backup
• Assignee: Alexander Lapin
• Reporter: Alexander Lapin
• Created: 11/Jun/24 13:51
• Updated: 21/Jun/24 16:19
• Resolved: 21/Jun/24 16:19

Description

Motivation

In order to implement read from backup logic it's required to provide an ability to retrieve assignments at best-effort manner.

Definition of Done

Following method should be added to the PlacementDriver

/**
 * Returns the future with either newest available tokenized assignments for the specified replication group id or {@code null} if
 * there are no such assignments. The future will be completed after clusterTime (meta storage safe time) will become greater or equal
 * to the clusterTimeToAwait parameter.
 *
 * @param replicationGroupId Replication group Id.
 * @param clusterTimeToAwait Cluster time to await.
 * @return Tokenized assignments.
 */
CompletableFuture<TokenizedAssignments> getAssignments(ReplicationGroupId replicationGroupId, HybridTimestamp clusterTimeToAwait); 

TokenizedAssignments is a common set of nodes along with associated token that allows to easely understand whether assignments were changed or not.

/**
 * Set of nodes along with associated token that is guaranteed to be changed if the set was changed.
 */
public interface TokenizedAssignments extends Serializable {
    /** Returns a set of nodes, represented by this assignments instance. */
    Set<Assignment> nodes();

    /** Returns a token associated with given assignments that is guaranteed to be changed if assignments were changed. */
    long token();
} 

Issue Links

• Dependency: IGNITE-22466 Sql. Support mapping to non-primary replicas
• links to: GitHub Pull Request #3947