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Merged
guozhangwang merged 15 commits into from
Apr 23, 2020
Merged

KAFKA-9823: Remember the sent generation for the coordinator request #8445

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115 changes: 87 additions & 28 deletions clients/src/main/java/org/apache/kafka/clients/consumer/internals/AbstractCoordinator.java
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Original file line number Diff line number Diff line change
Expand Up @@ -568,10 +568,14 @@ RequestFuture<ByteBuffer> sendJoinGroupRequest() {

int joinGroupTimeoutMs = Math.max(rebalanceConfig.rebalanceTimeoutMs, rebalanceConfig.rebalanceTimeoutMs + 5000);
return client.send(coordinator, requestBuilder, joinGroupTimeoutMs)
.compose(new JoinGroupResponseHandler());
.compose(new JoinGroupResponseHandler(generation));
}

private class JoinGroupResponseHandler extends CoordinatorResponseHandler<JoinGroupResponse, ByteBuffer> {
private JoinGroupResponseHandler(final Generation generation) {
super(generation);
}

@Override
public void handle(JoinGroupResponse joinResponse, RequestFuture<ByteBuffer> future) {
Errors error = joinResponse.error();
Expand Down Expand Up @@ -606,9 +610,12 @@ public void handle(JoinGroupResponse joinResponse, RequestFuture<ByteBuffer> fut
// backoff and retry
future.raise(error);
} else if (error == Errors.UNKNOWN_MEMBER_ID) {
// reset the member id and retry immediately
resetGenerationOnResponseError(ApiKeys.JOIN_GROUP, error);
log.debug("Attempt to join group failed due to unknown member id.");
log.debug("Attempt to join group failed due to unknown member id with {}.", sentGeneration);
// only need to reset the member id if generation has not been changed,
// then retry immediately
if (generationUnchanged())
resetGenerationOnResponseError(ApiKeys.JOIN_GROUP, error);

future.raise(error);
} else if (error == Errors.COORDINATOR_NOT_AVAILABLE
|| error == Errors.NOT_COORDINATOR) {
Expand All @@ -617,7 +624,10 @@ public void handle(JoinGroupResponse joinResponse, RequestFuture<ByteBuffer> fut
log.debug("Attempt to join group failed due to obsolete coordinator information: {}", error.message());
future.raise(error);
} else if (error == Errors.FENCED_INSTANCE_ID) {
log.error("Received fatal exception: group.instance.id gets fenced");
// for join-group request, even if the generation has changed we would not expect the instance id
// gets fenced, and hence we always treat this as a fatal error
log.error("Attempt to join group failed due to group instance id {} gets fenced with {}",

@hachikuji hachikuji Apr 16, 2020

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nit: can fix the grammar a little

Attempt to join group with generation {} failed because the group instance id {} has been fenced by another instance.

Similarly for a couple below

rebalanceConfig.groupInstanceId, sentGeneration);
future.raise(error);
} else if (error == Errors.INCONSISTENT_GROUP_PROTOCOL
|| error == Errors.INVALID_SESSION_TIMEOUT
Expand Down Expand Up @@ -708,10 +718,14 @@ private RequestFuture<ByteBuffer> sendSyncGroupRequest(SyncGroupRequest.Builder
if (coordinatorUnknown())
return RequestFuture.coordinatorNotAvailable();
return client.send(coordinator, requestBuilder)
.compose(new SyncGroupResponseHandler());
.compose(new SyncGroupResponseHandler(generation));
}

private class SyncGroupResponseHandler extends CoordinatorResponseHandler<SyncGroupResponse, ByteBuffer> {
private SyncGroupResponseHandler(final Generation generation) {
super(generation);
}

@Override
public void handle(SyncGroupResponse syncResponse,
RequestFuture<ByteBuffer> future) {
Expand All @@ -737,16 +751,21 @@ public void handle(SyncGroupResponse syncResponse,
log.debug("SyncGroup failed because the group began another rebalance");
future.raise(error);
} else if (error == Errors.FENCED_INSTANCE_ID) {
log.error("Received fatal exception: group.instance.id gets fenced");
// for sync-group request, even if the generation has changed we would not expect the instance id
// gets fenced, and hence we always treat this as a fatal error
log.error("SyncGroup failed with {} due to group.instance.id {} gets fenced",
sentGeneration, rebalanceConfig.groupInstanceId);
future.raise(error);
} else if (error == Errors.UNKNOWN_MEMBER_ID
|| error == Errors.ILLEGAL_GENERATION) {
log.debug("SyncGroup failed: {}", error.message());
resetGenerationOnResponseError(ApiKeys.SYNC_GROUP, error);
log.info("SyncGroup failed with {}: {}, would request re-join", sentGeneration, error.message());

@kkonstantine kkonstantine Apr 16, 2020

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nit: would request re-join or will request re-join?

More importantly the log message is outside of the if branch below. But if generationUnchanged() is false, then re-join won't be requested, at least not by calling resetGenerationOnResponseError -> resetGeneration -> rejoinNeeded = true;. a) is that safe (as I ask below) b) is the log message printed accurate if there's a chance that re-join is not requested (accuracy of log messages is very crucial here, because usually that's all we have when troubleshooting rebalances).

@guozhangwang guozhangwang Apr 16, 2020

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Note on the caller joinGroupIfNeeded, when the future fails (here, with either illegal generation and unknown member) then the the join-group would be resent. The only thing we skip is the resetting of the generation since it has already changed.

@kkonstantine kkonstantine Apr 20, 2020

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Not sure how this comment was changed, but this still doesn't read well for me.
Still seems that the message should say ... will request re-join"

if (generationUnchanged())

@kkonstantine kkonstantine Apr 16, 2020

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Hey @guozhangwang.
Trying to understand if any of these changes have implications for the WorkerCoordinator too.

What I've observed is that if the WorkerCoordinator fails to receive a valid SyncGroup request, it may miss several generations until it succeeds again. Is the branch here safe? resetGenerationOnResponseError will be called (and therefore rejoin will be requested) only if generationUnchanged returns true. Is there any risk that we suppress any useful retries to rejoin?

@guozhangwang guozhangwang Apr 16, 2020

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The rationale is that if the generation has changed, it is either reset by the heartbeat thread in which case the generation is reset and rejoin is already requested, or it is changed by another join-group request; but since inside AbstractCoordinator we will only have one in-flight request at a given time the second scenario should not happen. So the only possibility is the heartbeat resetting.

@kkonstantine kkonstantine Apr 20, 2020

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Makes sense. Thanks

resetGenerationOnResponseError(ApiKeys.SYNC_GROUP, error);

future.raise(error);
} else if (error == Errors.COORDINATOR_NOT_AVAILABLE
|| error == Errors.NOT_COORDINATOR) {
log.debug("SyncGroup failed: {}", error.message());
log.debug("SyncGroup failed: {}, marking coordinator unknown", error.message());
markCoordinatorUnknown();
future.raise(error);
} else {
Expand Down Expand Up @@ -890,8 +909,8 @@ protected synchronized String memberId() {
}

private synchronized void resetGeneration() {
this.rejoinNeeded = true;
this.generation = Generation.NO_GENERATION;
rejoinNeeded = true;
generation = Generation.NO_GENERATION;
}

synchronized void resetGenerationOnResponseError(ApiKeys api, Errors error) {
Expand Down Expand Up @@ -989,7 +1008,7 @@ public synchronized RequestFuture<Void> maybeLeaveGroup(String leaveReason) {
Collections.singletonList(new MemberIdentity().setMemberId(generation.memberId))
);

future = client.send(coordinator, request).compose(new LeaveGroupResponseHandler());
future = client.send(coordinator, request).compose(new LeaveGroupResponseHandler(generation));
client.pollNoWakeup();
}

Expand All @@ -1003,6 +1022,10 @@ protected boolean isDynamicMember() {
}

private class LeaveGroupResponseHandler extends CoordinatorResponseHandler<LeaveGroupResponse, Void> {
private LeaveGroupResponseHandler(final Generation generation) {
super(generation);
}

@Override
public void handle(LeaveGroupResponse leaveResponse, RequestFuture<Void> future) {
final List<MemberResponse> members = leaveResponse.memberResponses();
Expand All @@ -1013,10 +1036,10 @@ public void handle(LeaveGroupResponse leaveResponse, RequestFuture<Void> future)

final Errors error = leaveResponse.error();
if (error == Errors.NONE) {
log.debug("LeaveGroup request returned successfully");
log.debug("LeaveGroup response with {} returned successfully: {}", sentGeneration, response);
future.complete(null);
} else {
log.error("LeaveGroup request failed with error: {}", error.message());
log.error("LeaveGroup response with {} failed with error: {}", sentGeneration, error.message());

@hachikuji hachikuji Apr 16, 2020

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nit: seems the original was a little more accurate? The response did not fail; it just contained an error indicating the request had failed.

future.raise(error);
}
}
Expand All @@ -1037,10 +1060,8 @@ synchronized RequestFuture<Void> sendHeartbeatRequest() {
}

private class HeartbeatResponseHandler extends CoordinatorResponseHandler<HeartbeatResponse, Void> {
private final Generation sentGeneration;

private HeartbeatResponseHandler(final Generation generation) {
this.sentGeneration = generation;
super(generation);
}

@Override
Expand All @@ -1061,16 +1082,36 @@ public void handle(HeartbeatResponse heartbeatResponse, RequestFuture<Void> futu
requestRejoin();
future.raise(error);
} else if (error == Errors.ILLEGAL_GENERATION) {
log.info("Attempt to heartbeat failed since generation {} is not current", sentGeneration.generationId);
resetGenerationOnResponseError(ApiKeys.HEARTBEAT, error);
future.raise(error);
if (generationUnchanged()) {
log.info("Attempt to heartbeat failed since current {} is not valid, resetting generation", sentGeneration);
resetGenerationOnResponseError(ApiKeys.HEARTBEAT, error);
future.raise(error);
} else {
// if the generation has changed, then ignore this error
log.info("Attempt to heartbeat failed since old {} is not valid, ignoring the error", sentGeneration);
future.complete(null);
}
} else if (error == Errors.FENCED_INSTANCE_ID) {
log.error("Received fatal exception: group.instance.id gets fenced");
future.raise(error);
if (generationUnchanged()) {
log.info("Attempt to heartbeat failed since current {} gets fenced with group instance id {}",
sentGeneration, rebalanceConfig.groupInstanceId);
future.raise(error);
} else {
// if the generation has changed, then ignore this error

@hachikuji hachikuji Apr 14, 2020

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Not sure why we ignore fenced errors here but not in the JoinGroup/SyncGroup handlers.

@guozhangwang guozhangwang Apr 15, 2020

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As explained in the PR description, I intentionally make the logic differently: the rationale is that for join / sync we should only have one request in-flight at a given time, and at that time if the generation has changed it should be from the heartbeat error handling that resets it; for this case this client should have not re-joined and replaced its member.id, so if the error returns it still indicates another member with the same instance.id has replaced the member.id.

For heartbeat though, we've observed it is possible that, 1) heartbeat sent, 2) the same member rejoins group, gets a new member.id, 3) the previous heartbeat is handled and the error set. In this case we should not treat it as fatal.

log.info("Attempt to heartbeat failed since old {} gets fenced with group instance id {}, " +
"ignoring the error", sentGeneration, rebalanceConfig.groupInstanceId);
future.complete(null);
}
} else if (error == Errors.UNKNOWN_MEMBER_ID) {
log.info("Attempt to heartbeat failed since member id {} is not valid.", sentGeneration.memberId);
resetGenerationOnResponseError(ApiKeys.HEARTBEAT, error);
future.raise(error);
if (generationUnchanged()) {

@abbccdda abbccdda Apr 8, 2020

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In other response handlers, we combine UNKNOWN_MEMBER_ID and ILLEGAL_GENERATION cases. Do you think we could also consolidate here as well?

@hachikuji hachikuji Apr 14, 2020

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Yes, I agree we should try to consolidate. Looking at this handler alone, we have basically the same code for ILLEGAL_GENERATION, UNKNOWN_MEMBER_ID, and FENCED_INSTANCE_ID.

@guozhangwang guozhangwang Apr 15, 2020

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SG, let me try it out.

log.info("Attempt to heartbeat failed since current {} member id is unknown, resetting generation", sentGeneration);
resetGenerationOnResponseError(ApiKeys.HEARTBEAT, error);
future.raise(error);
} else {
// if the generation has changed, then ignore this error
log.info("Attempt to heartbeat failed since old {} member id is unknown, ignoring the error", sentGeneration);
future.complete(null);
}
} else if (error == Errors.GROUP_AUTHORIZATION_FAILED) {
future.raise(GroupAuthorizationException.forGroupId(rebalanceConfig.groupId));
} else {
Expand All @@ -1080,7 +1121,12 @@ public void handle(HeartbeatResponse heartbeatResponse, RequestFuture<Void> futu
}

protected abstract class CoordinatorResponseHandler<R, T> extends RequestFutureAdapter<ClientResponse, T> {
protected ClientResponse response;
CoordinatorResponseHandler(final Generation generation) {
this.sentGeneration = generation;
}

final Generation sentGeneration;
ClientResponse response;

public abstract void handle(R response, RequestFuture<T> future);

Expand All @@ -1106,6 +1152,11 @@ public void onSuccess(ClientResponse clientResponse, RequestFuture<T> future) {
}
}

boolean generationUnchanged() {
synchronized (AbstractCoordinator.this) {
return generation.equals(sentGeneration);
}
}
}

protected Meter createMeter(Metrics metrics, String groupName, String baseName, String descriptiveName) {
Expand Down Expand Up @@ -1421,7 +1472,7 @@ private static class UnjoinedGroupException extends RetriableException {
}

// For testing only below
public Heartbeat heartbeat() {
final Heartbeat heartbeat() {
return heartbeat;
}

Expand Down Expand Up @@ -1449,4 +1500,12 @@ final boolean hasUnknownGeneration() {
final boolean hasValidMemberId() {
return generation != Generation.NO_GENERATION && generation.hasMemberId();
}

final void setNewGeneration(final Generation generation) {

@hachikuji hachikuji Apr 14, 2020

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Should we make these methods synchronized?

@guozhangwang guozhangwang Apr 15, 2020

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These functions are only used in non-integration unit tests so I think it is not necessary. LMK if you have a strong motivation?

@hachikuji hachikuji Apr 15, 2020

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Just because they are exposed. If they ultimately got used in unit tests involving concurrent threads, we would need them to be synchronized. Seems there's no downside to being on the safe side?

@guozhangwang guozhangwang Apr 15, 2020

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Yup I think so, let me synchronize this then :)

this.generation = generation;
}

final void setNewState(final MemberState state) {
this.state = state;
}
}
61 changes: 46 additions & 15 deletions clients/src/main/java/org/apache/kafka/clients/consumer/internals/ConsumerCoordinator.java
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Original file line number Diff line number Diff line change
Expand Up @@ -272,6 +272,18 @@ private void maybeUpdateJoinedSubscription(Set<TopicPartition> assignedPartition
}
}

private Exception invokeOnAssignment(final ConsumerPartitionAssignor assignor, final Assignment assignment) {
log.info("Notifying assignor about the new {}", assignment);

try {
assignor.onAssignment(assignment, groupMetadata);
} catch (Exception e) {
return e;
}

return null;
}

private Exception invokePartitionsAssigned(final Set<TopicPartition> assignedPartitions) {
log.info("Adding newly assigned partitions: {}", Utils.join(assignedPartitions, ", "));

Expand Down Expand Up @@ -351,7 +363,7 @@ protected void onJoinComplete(int generation,

// should at least encode the short version
if (assignmentBuffer.remaining() < 2)
throw new IllegalStateException("There is insufficient bytes available to read assignment from the sync-group response (" +
throw new IllegalStateException("There are insufficient bytes available to read assignment from the sync-group response (" +
"actual byte size " + assignmentBuffer.remaining() + ") , this is not expected; " +
"it is possible that the leader's assign function is buggy and did not return any assignment for this member, " +
"or because static member is configured and the protocol is buggy hence did not get the assignment for this member");
Expand Down Expand Up @@ -406,11 +418,7 @@ protected void onJoinComplete(int generation,
maybeUpdateJoinedSubscription(assignedPartitions);

// Catch any exception here to make sure we could complete the user callback.
try {
assignor.onAssignment(assignment, groupMetadata);
} catch (Exception e) {
firstException.compareAndSet(null, e);
}
firstException.compareAndSet(null, invokeOnAssignment(assignor, assignment));

// Reschedule the auto commit starting from now
if (autoCommitEnabled)
Expand Down Expand Up @@ -1064,10 +1072,12 @@ public void onComplete(Map<TopicPartition, OffsetAndMetadata> offsets, Exception
* which returns a request future that can be polled in the case of a synchronous commit or ignored in the
* asynchronous case.
*
* NOTE: This is visible only for testing
*
* @param offsets The list of offsets per partition that should be committed.
* @return A request future whose value indicates whether the commit was successful or not
*/
private RequestFuture<Void> sendOffsetCommitRequest(final Map<TopicPartition, OffsetAndMetadata> offsets) {
RequestFuture<Void> sendOffsetCommitRequest(final Map<TopicPartition, OffsetAndMetadata> offsets) {
if (offsets.isEmpty())
return RequestFuture.voidSuccess();

Expand Down Expand Up @@ -1135,14 +1145,14 @@ private RequestFuture<Void> sendOffsetCommitRequest(final Map<TopicPartition, Of
log.trace("Sending OffsetCommit request with {} to coordinator {}", offsets, coordinator);

return client.send(coordinator, builder)
.compose(new OffsetCommitResponseHandler(offsets));
.compose(new OffsetCommitResponseHandler(offsets, generation));
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}

private class OffsetCommitResponseHandler extends CoordinatorResponseHandler<OffsetCommitResponse, Void> {

private final Map<TopicPartition, OffsetAndMetadata> offsets;

private OffsetCommitResponseHandler(Map<TopicPartition, OffsetAndMetadata> offsets) {
private OffsetCommitResponseHandler(Map<TopicPartition, OffsetAndMetadata> offsets, Generation generation) {
super(generation);
this.offsets = offsets;
}

Expand Down Expand Up @@ -1190,8 +1200,16 @@ public void handle(OffsetCommitResponse commitResponse, RequestFuture<Void> futu
future.raise(error);
return;
} else if (error == Errors.FENCED_INSTANCE_ID) {
log.error("Received fatal exception: group.instance.id gets fenced");
future.raise(error);
log.info("OffsetCommit failed with {} due to group instance id {} fenced", sentGeneration, rebalanceConfig.groupInstanceId);

// if the generation has changed, do not raise the fatal error but rebalance-in-progress
if (generationUnchanged()) {

@abbccdda abbccdda Apr 8, 2020

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Why could we still survive from a fenced instance id in commit request?

@guozhangwang guozhangwang Apr 15, 2020

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No we could not "survive", the point of throwing RebalanceInProgress is not to survive, but to give a different error case to the caller that it do not necessarily have to exit as zombie but could retry.

future.raise(error);
} else {
future.raise(new RebalanceInProgressException("Offset commit cannot be completed since the " +
"consumer member's old generation is fenced by its group instance id, it is possible that " +
"this consumer has already participated another rebalance and got a new generation"));
}
return;
} else if (error == Errors.REBALANCE_IN_PROGRESS) {
/* Consumer should not try to commit offset in between join-group and sync-group,
Expand All @@ -1209,9 +1227,18 @@ public void handle(OffsetCommitResponse commitResponse, RequestFuture<Void> futu
return;
} else if (error == Errors.UNKNOWN_MEMBER_ID
|| error == Errors.ILLEGAL_GENERATION) {
// need to reset generation and re-join group
resetGenerationOnResponseError(ApiKeys.OFFSET_COMMIT, error);
future.raise(new CommitFailedException());
log.info("OffsetCommit failed with {}: {}", sentGeneration, error.message());

// only need to reset generation and re-join group if generation has not changed;
// otherwise only raise rebalance-in-progress error
if (generationUnchanged()) {
resetGenerationOnResponseError(ApiKeys.OFFSET_COMMIT, error);
future.raise(new CommitFailedException());
} else {
future.raise(new RebalanceInProgressException("Offset commit cannot be completed since the " +

@ableegoldman ableegoldman Apr 24, 2020

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This seems a bit misleading, because the consumer is not actually participating in an ongoing rebalance (yet)

@ableegoldman ableegoldman Apr 24, 2020

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@guozhangwang can you elaborate on why we don't just throw CommitFailedException here? It seems like it must be the case that the caller is a zombie and should get that exception to alert it, not the RebalanceInProgressException which seems to indicate it might be recoverable

@guozhangwang guozhangwang Apr 24, 2020

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If the generation has changed since the commit request is sent, then it is likely that it has participated in a new rebalance (and hence get a new generation), or it has reset its generation due to the heartbeat failure. So this commit failure is recoverable.

@ableegoldman ableegoldman Apr 24, 2020

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Chatted about this offline, will just leave the concrete proposal here:

...
} else {
    if (state == MemberState.REBALANCING) {
        future.raise(new RebalanceInProgressException(...)
    } else {
        future.raise(new CommitFailedException(...)
    }
}

@ableegoldman ableegoldman Apr 24, 2020

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The reasoning being that we use CommitFailedException to signal we have dropped out of the group, and RebalanceInProgressException to signal that a rebalance is in progress. There are two cases to consider (within the general case of the generation having changed):

  1. If the generation is unknown and the state is STABLE this means we have dropped out of the group, but haven't yet rejoined and haven't invoked onPartitionsLost --> should throw CommitFailed
  2. If the generation is unknown and the state is REBALANCING this means we dropped out of the group, but have already noticed and rejoined, and already invoked onPartitionsLost --> should throw RebalanceInProgress

Note that if we dropped out of the group and already completed the rejoin, the state will be STABLE again but the generation will also have been set so this case does not apply. Basically, we want to keep CommitFailedException to indicate that the consumer definitely dropped out and will have to rejoin, which is the case in 1. above

"consumer member's generation is already stale, meaning it has already participated another rebalance and " +
"got a new generation. You can try completing the rebalance by calling poll() and then retry commit again"));
}
return;
} else {
future.raise(new KafkaException("Unexpected error in commit: " + error.message()));
Expand Down Expand Up @@ -1253,6 +1280,10 @@ private RequestFuture<Map<TopicPartition, OffsetAndMetadata>> sendOffsetFetchReq
}

private class OffsetFetchResponseHandler extends CoordinatorResponseHandler<OffsetFetchResponse, Map<TopicPartition, OffsetAndMetadata>> {
private OffsetFetchResponseHandler() {
super(Generation.NO_GENERATION);
}

@Override
public void handle(OffsetFetchResponse response, RequestFuture<Map<TopicPartition, OffsetAndMetadata>> future) {
if (response.hasError()) {
Expand Down
5 changes: 5 additions & 0 deletions clients/src/main/java/org/apache/kafka/common/requests/LeaveGroupResponse.java
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Original file line number Diff line number Diff line change
Expand Up @@ -134,6 +134,11 @@ public Map<Errors, Integer> errorCounts() {
return combinedErrorCounts;
}

@Override
public String toString() {
return data.toString();
}

@Override
public Struct toStruct(short version) {
return data.toStruct(version);
Expand Down
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