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https://issues.apache.org/jira/browse/IGNITE-20646?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Vyacheslav Koptilin updated IGNITE-20646:
-----------------------------------------
Labels: ignite-3 (was: )
> Consider using CLOCK_SKEW unaware await/getPrimaryReplica()
> -----------------------------------------------------------
>
> Key: IGNITE-20646
> URL: https://issues.apache.org/jira/browse/IGNITE-20646
> Project: Ignite
> Issue Type: Improvement
> Reporter: Alexander Lapin
> Priority: Major
> Labels: ignite-3
>
> h3. Motivation
> [Vladislav
> Pyatkov|https://issues.apache.org/jira/secure/ViewProfile.jspa?name=vpyatkov]
> has strong point that current CLOCK_SKEW aware implementation of
> await/getPrimaryReplica should be removed, meaning that we should compare
> expirationTimestamp with propagated one without error(CLOCK_SKEW). Same as
> for waiting. Current CLOC_SKEW aware approach is specified in
> org.apache.ignite.internal.placementdriver.PlacementDriver javadocs and
> guarantees that if primary replica is visible from await on node A it'll be
> visible thought get on any other node.
> h3. Definition of Done
> We should prepare full set of pros and cons for each option. Whether they are
> correct? Which one is better from the performance point of view? Which one is
> simpler?
> h3. UPD
> The issue is deeper than we described it here. The root cause of the issue is
> the placement driver API, which is inappropriate to use for someone who has
> never seen the implementation. I mean the two methods, awaitPrimaryReplica
> and getPrimaryReplica, because both methods get a timestamp from parameters
> but have the internal proposal that the timestamp is the current timestamp
> for this node. Nevertheless, functionality is required.
> My advise:
> {code}
> public CompletableFuture<ReplicaMeta> awaitPrimaryReplica(
> ReplicationGroupId groupId,
> long timeout,
> TimeUnit unit
> ) {
> return inBusyLockAsync(busyLock, () -> {
> CompletableFuture<ReplicaMeta> fut = new CompletableFuture<>();
> EventListener<PrimaryReplicaEventParameters> lnsr = (parameters,
> exception) -> {
> if (parameters.groupId().equals(groupId)) {
> fut.complete(leases.leaseByGroupId().get(groupId));
> return completedFuture(true);
> }
> return completedFuture(false);
> };
> listen(PRIMARY_REPLICA_ELECTED, lnsr);
> // It is a pseudocode, basically. You should get the lease from
> the event parameter in the project code.
> Lease lease = leases.leaseByGroupId().getOrDefault(groupId,
> EMPTY_LEASE);
> if (lease.isAccepted()) {
> removeListener(PRIMARY_REPLICA_ELECTED, lnsr);
> fut.complete(lease);
> }
> return fut;
> });
> }
> public CompletableFuture<ReplicaMeta>
> getPrimaryReplica(ReplicationGroupId replicationGroupId, HybridTimestamp
> timestamp) {
> return inBusyLockAsync(busyLock, () -> {
> Lease lease =
> leases.leaseByGroupId().getOrDefault(replicationGroupId, EMPTY_LEASE);
> if (lease.isAccepted() &&
> lease.getExpirationTime().compareTo(timestamp) > 0 &&
> lease.getStartTime().compareTo(timestamp) < 0
> ) {
> return completedFuture(lease);
> }
> // TODO: Here we have to compare with the last update placement
> driver timestamp. Unfortunately, we do not save the
> // timestamp in the lease updater
> (Updater#updateLeaseBatchInternal) thread. It must be done in the future.
> // Based on Meta storage, safe time is the wrong solution because
> the lease timestamp does not depend on the safe time.
> return msManager
> .clusterTime()
> .waitFor(timestamp.addPhysicalTime(CLOCK_SKEW))
> .thenApply(ignored -> inBusyLock(busyLock, () -> {
> Lease lease0 =
> leases.leaseByGroupId().getOrDefault(replicationGroupId, EMPTY_LEASE);
> if (lease.isAccepted() &&
>
> lease.getExpirationTime().compareTo(timestamp) > 0 &&
> lease.getStartTime().compareTo(timestamp) < 0
> ) {
> return lease0;
> } else {
> return null;
> }
> }));
> });
> }
> {code}
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