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https://issues.apache.org/jira/browse/IGNITE-19428?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17724806#comment-17724806
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Denis Chudov commented on IGNITE-19428:
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[~alapin] LGTM.
> Implement placement driver API
> ------------------------------
>
> Key: IGNITE-19428
> URL: https://issues.apache.org/jira/browse/IGNITE-19428
> Project: Ignite
> Issue Type: Improvement
> Reporter: Alexander Lapin
> Assignee: Alexander Lapin
> Priority: Major
> Labels: iep-101, ignite-3
>
> h3. Motivation
> In order to implement RW part of tx protocol it's required to check whether
> we touch same primary replica that was previously enlisted and await primary
> replica appearance on group readiness. Currently it's implemented using same
> raft-leader check on top of retry logic with throttling which is inefficient
> and doesn't support overall idea of hiding replication protocol details under
> replicas umbrella.
> h3. Definition of done
> Long story short, it's required to implement following API (exact one or
> similar)
> {code:java}
> /**
> * Returns a future for the primary replica for the specified replication
> group whose expiration time (the right border of the
> * corresponding lease interval) is greater than or equal to the
> timestamp passed as a parameter. Please pay attention that there are
> * no restriction on the lease start time (left border), it can either be
> less or greater than or equal to proposed timestamp.
> * Given method will await for an appropriate primary replica appearance
> if there's no already existing one. Such awaiting logic is
> * unbounded, so it's mandatory to use explicit await termination like
> {@code orTimeout}.
> *
> * @param replicationGroupId Replication group id.
> * @param timestamp Timestamp reference value.
> * @return Primary replica future.
> */
> public CompletableFuture<ReplicaMeta>
> awaitPrimaryReplica(ReplicationGroupId replicationGroupId, HybridTimestamp
> timestamp) {
> return CompletableFuture.completedFuture(null);
> }
> /**
> * Same as {@link
> PlacementDriverManager#awaitPrimaryReplica(ReplicationGroupId,
> HybridTimestamp)} despite the fact that given method
> * won't await for an appropriate primary replica appearance if there's
> no already existing one, in that case null will be returned.
> *
> * @param replicationGroupId Replication group id.
> * @param timestamp Timestamp reference value.
> * @return Primary replica future.
> */
> public CompletableFuture<ReplicaMeta>
> getPrimaryReplica(ReplicationGroupId replicationGroupId, HybridTimestamp
> timestamp) {
> return CompletableFuture.completedFuture(null);
> } {code}
> h3. Implementation Notes
> Seems reasonable to reuse PendingComparableValuesTracker logic in order to
> implement aforementioned API. Some PendingComparableValuesTracker
> enhancement are required though, see
> https://issues.apache.org/jira/browse/IGNITE-18859 for more details.
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