Source:
public void handle(SyncGroupResponse syncResponse, RequestFuture<ByteBuffer> future) { Errors error = syncResponse.error(); if (isProtocolTypeInconsistent(syncResponse.data.protocolType()) || isProtocolNameInconsistent(syncResponse.data.protocolName())) { log.debug("SyngGroup failed: Received inconsistent ProtocolType ({}) and/or ProtocolName ({})", syncResponse.data.protocolType(), syncResponse.data.protocolName()); future.raise(Errors.INCONSISTENT_GROUP_PROTOCOL); } else if (error == Errors.NONE) { sensors.syncSensor.record(response.requestLatencyMs()); future.complete(ByteBuffer.wrap(syncResponse.data.assignment())); } else { requestRejoin(); if (error == Errors.GROUP_AUTHORIZATION_FAILED) { future.raise(GroupAuthorizationException.forGroupId(rebalanceConfig.groupId)); } else if (error == Errors.REBALANCE_IN_PROGRESS) { 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"); 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); future.raise(error); } else if (error == Errors.COORDINATOR_NOT_AVAILABLE || error == Errors.NOT_COORDINATOR) { log.debug("SyncGroup failed: {}", error.message()); markCoordinatorUnknown(); future.raise(error); } else { future.raise(new KafkaException("Unexpected error from SyncGroup: " + error.message())); } } }

Target:
public void handle(SyncGroupResponse syncResponse, RequestFuture<ByteBuffer> future) { Errors error = syncResponse.error(); if (error == Errors.NONE) { if (isProtocolTypeInconsistent(syncResponse.data.protocolType())) { log.debug("SyncGroup failed due to inconsistent Protocol Type, received but expected {}", syncResponse.data.protocolType(), protocolType()); future.raise(Errors.INCONSISTENT_GROUP_PROTOCOL); } else if (isProtocolNameInconsistent(syncResponse.data.protocolName())) { log.debug("SyncGroup failed due to inconsistent Protocol Name, received but expected {}", syncResponse.data.protocolName(), generation().protocolName); future.raise(Errors.INCONSISTENT_GROUP_PROTOCOL); } else { sensors.syncSensor.record(response.requestLatencyMs()); future.complete(ByteBuffer.wrap(syncResponse.data.assignment())); } } else { requestRejoin(); if (error == Errors.GROUP_AUTHORIZATION_FAILED) { future.raise(GroupAuthorizationException.forGroupId(rebalanceConfig.groupId)); } else if (error == Errors.REBALANCE_IN_PROGRESS) { 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"); 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); future.raise(error); } else if (error == Errors.COORDINATOR_NOT_AVAILABLE || error == Errors.NOT_COORDINATOR) { log.debug("SyncGroup failed: {}", error.message()); markCoordinatorUnknown(); future.raise(error); } else { future.raise(new KafkaException("Unexpected error from SyncGroup: " + error.message())); } } }