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Posted to jira@kafka.apache.org by GitBox <gi...@apache.org> on 2021/02/10 16:32:17 UTC
[GitHub] [kafka] mumrah commented on a change in pull request #10095: MINOR: Introduce the KIP-500 Broker lifecycle manager
mumrah commented on a change in pull request #10095:
URL: https://github.com/apache/kafka/pull/10095#discussion_r573845682
##########
File path: core/src/main/scala/kafka/server/BrokerLifecycleManager.scala
##########
@@ -0,0 +1,457 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package kafka.server
+
+import java.util
+import java.util.concurrent.TimeUnit.{MILLISECONDS, NANOSECONDS}
+import java.util.concurrent.{CompletableFuture, TimeUnit}
+import kafka.utils.Logging
+import org.apache.kafka.clients.ClientResponse
+import org.apache.kafka.common.Uuid
+import org.apache.kafka.common.message.BrokerRegistrationRequestData.ListenerCollection
+import org.apache.kafka.common.message.{BrokerHeartbeatRequestData, BrokerRegistrationRequestData}
+import org.apache.kafka.common.protocol.Errors
+import org.apache.kafka.common.requests.{BrokerHeartbeatRequest, BrokerHeartbeatResponse, BrokerRegistrationRequest, BrokerRegistrationResponse}
+import org.apache.kafka.metadata.{BrokerState, VersionRange}
+import org.apache.kafka.queue.EventQueue.DeadlineFunction
+import org.apache.kafka.common.utils.{ExponentialBackoff, LogContext, Time}
+import org.apache.kafka.queue.{EventQueue, KafkaEventQueue}
+import scala.jdk.CollectionConverters._
+
+
+class BrokerLifecycleManager(val config: KafkaConfig,
+ val time: Time,
+ val threadNamePrefix: Option[String]) extends Logging {
+ val logContext = new LogContext(s"[BrokerLifecycleManager id=${config.nodeId}] ")
+
+ this.logIdent = logContext.logPrefix()
+
+ /**
+ * The broker id.
+ */
+ private val nodeId = config.nodeId
+
+ /**
+ * The broker rack, or null if there is no configured rack.
+ */
+ private val rack = config.rack.orNull
+
+ /**
+ * How long to wait for registration to succeed before failing the startup process.
+ */
+ private val initialTimeoutNs = NANOSECONDS.
+ convert(config.initialRegistrationTimeoutMs.longValue(), TimeUnit.MILLISECONDS)
+
+ /**
+ * The exponential backoff to use for resending communication.
+ */
+ private val resendExponentialBackoff =
+ new ExponentialBackoff(100, 2, config.brokerSessionTimeoutMs.toLong, 0.1)
+
+ /**
+ * The number of tries we've tried to communicate.
+ */
+ private var failedAttempts = 0L
+
+ /**
+ * The broker incarnation ID. This ID uniquely identifies each time we start the broker
+ */
+ val incarnationId = Uuid.randomUuid()
+
+ /**
+ * A future which is completed just as soon as the broker has caught up with the latest
+ * metadata offset for the first time.
+ */
+ val initialCatchUpFuture = new CompletableFuture[Void]()
+
+ /**
+ * A future which is completed when controlled shutdown is done.
+ */
+ val controlledShutdownFuture = new CompletableFuture[Void]()
+
+ /**
+ * The broker epoch, or -1 if the broker has not yet registered.
+ * This variable can only be written from the event queue thread.
+ */
+ @volatile private var _brokerEpoch = -1L
+
+ /**
+ * The current broker state.
+ * This variable can only be written from the event queue thread.
+ */
+ @volatile private var _state = BrokerState.NOT_RUNNING
+
+ /**
+ * A callback function which gives this manager the current highest metadata offset.
+ * This function must be thread-safe.
+ */
+ private var _highestMetadataOffsetProvider: () => Long = null
+
+ /**
+ * True only if we are ready to unfence the broker.
+ * This variable can only be accessed from the event queue thread.
+ */
+ private var readyToUnfence = false
+
+ /**
+ * True if we sent a heartbeat to the active controller requesting controlled
+ * shutdown.
+ */
+ private var gotControlledShutdownResponse = false
+
+ /**
+ * Whether or not we this broker is registered with the controller quorum.
+ * This variable can only be accessed from the event queue thread.
+ */
+ private var registered = false
+
+ /**
+ * True if the initial registration succeeded.
+ * This variable can only be accessed from the event queue thread.
+ */
+ private var initialRegistrationSucceeded = false
+
+ /**
+ * The cluster ID, or null if this manager has not been started yet.
+ * This variable can only be accessed from the event queue thread.
+ */
+ private var _clusterId: Uuid = null
Review comment:
Why are some members prefixed with an underscore?
##########
File path: core/src/main/scala/kafka/server/BrokerLifecycleManager.scala
##########
@@ -0,0 +1,457 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package kafka.server
+
+import java.util
+import java.util.concurrent.TimeUnit.{MILLISECONDS, NANOSECONDS}
+import java.util.concurrent.{CompletableFuture, TimeUnit}
+import kafka.utils.Logging
+import org.apache.kafka.clients.ClientResponse
+import org.apache.kafka.common.Uuid
+import org.apache.kafka.common.message.BrokerRegistrationRequestData.ListenerCollection
+import org.apache.kafka.common.message.{BrokerHeartbeatRequestData, BrokerRegistrationRequestData}
+import org.apache.kafka.common.protocol.Errors
+import org.apache.kafka.common.requests.{BrokerHeartbeatRequest, BrokerHeartbeatResponse, BrokerRegistrationRequest, BrokerRegistrationResponse}
+import org.apache.kafka.metadata.{BrokerState, VersionRange}
+import org.apache.kafka.queue.EventQueue.DeadlineFunction
+import org.apache.kafka.common.utils.{ExponentialBackoff, LogContext, Time}
+import org.apache.kafka.queue.{EventQueue, KafkaEventQueue}
+import scala.jdk.CollectionConverters._
+
+
+class BrokerLifecycleManager(val config: KafkaConfig,
+ val time: Time,
+ val threadNamePrefix: Option[String]) extends Logging {
+ val logContext = new LogContext(s"[BrokerLifecycleManager id=${config.nodeId}] ")
+
+ this.logIdent = logContext.logPrefix()
+
+ /**
+ * The broker id.
+ */
+ private val nodeId = config.nodeId
+
+ /**
+ * The broker rack, or null if there is no configured rack.
+ */
+ private val rack = config.rack.orNull
+
+ /**
+ * How long to wait for registration to succeed before failing the startup process.
+ */
+ private val initialTimeoutNs = NANOSECONDS.
+ convert(config.initialRegistrationTimeoutMs.longValue(), TimeUnit.MILLISECONDS)
+
+ /**
+ * The exponential backoff to use for resending communication.
+ */
+ private val resendExponentialBackoff =
+ new ExponentialBackoff(100, 2, config.brokerSessionTimeoutMs.toLong, 0.1)
+
+ /**
+ * The number of tries we've tried to communicate.
+ */
+ private var failedAttempts = 0L
+
+ /**
+ * The broker incarnation ID. This ID uniquely identifies each time we start the broker
+ */
+ val incarnationId = Uuid.randomUuid()
+
+ /**
+ * A future which is completed just as soon as the broker has caught up with the latest
+ * metadata offset for the first time.
+ */
+ val initialCatchUpFuture = new CompletableFuture[Void]()
+
+ /**
+ * A future which is completed when controlled shutdown is done.
+ */
+ val controlledShutdownFuture = new CompletableFuture[Void]()
+
+ /**
+ * The broker epoch, or -1 if the broker has not yet registered.
+ * This variable can only be written from the event queue thread.
+ */
+ @volatile private var _brokerEpoch = -1L
+
+ /**
+ * The current broker state.
+ * This variable can only be written from the event queue thread.
+ */
+ @volatile private var _state = BrokerState.NOT_RUNNING
+
+ /**
+ * A callback function which gives this manager the current highest metadata offset.
+ * This function must be thread-safe.
+ */
+ private var _highestMetadataOffsetProvider: () => Long = null
+
+ /**
+ * True only if we are ready to unfence the broker.
+ * This variable can only be accessed from the event queue thread.
+ */
+ private var readyToUnfence = false
+
+ /**
+ * True if we sent a heartbeat to the active controller requesting controlled
+ * shutdown.
+ */
+ private var gotControlledShutdownResponse = false
+
+ /**
+ * Whether or not we this broker is registered with the controller quorum.
+ * This variable can only be accessed from the event queue thread.
+ */
+ private var registered = false
+
+ /**
+ * True if the initial registration succeeded.
+ * This variable can only be accessed from the event queue thread.
+ */
+ private var initialRegistrationSucceeded = false
+
+ /**
+ * The cluster ID, or null if this manager has not been started yet.
+ * This variable can only be accessed from the event queue thread.
+ */
+ private var _clusterId: Uuid = null
+
+ /**
+ * The listeners which this broker advertises.
+ */
+ private var _advertisedListeners: ListenerCollection = null
+
+ /**
+ * The features supported by this broker.
+ */
+ private var _supportedFeatures: util.Map[String, VersionRange] = null
+
+ /**
+ * The channel manager, or null if this manager has not been started yet.
+ * This variable can only be accessed from the event queue thread.
+ */
+ var _channelManager: BrokerToControllerChannelManager = null
+
+ /**
+ * The event queue.
+ */
+ val eventQueue = new KafkaEventQueue(time, logContext, threadNamePrefix.getOrElse(""))
+
+ /**
+ * Start the BrokerLifecycleManager.
+ *
+ * @param highestMetadataOffsetProvider Provides the current highest metadata offset.
+ * @param channelManager The brokerToControllerChannelManager to use.
+ * @param clusterId The cluster ID.
+ */
+ def start(highestMetadataOffsetProvider: () => Long,
+ channelManager: BrokerToControllerChannelManager,
+ clusterId: Uuid,
+ advertisedListeners: ListenerCollection,
+ supportedFeatures: util.Map[String, VersionRange]): Unit = {
+ eventQueue.append(new StartupEvent(highestMetadataOffsetProvider,
+ channelManager, clusterId, advertisedListeners, supportedFeatures))
+ }
+
+ def setReadyToUnfence(): Unit = {
+ eventQueue.append(new SetReadyToUnfenceEvent())
+ }
+
+ def brokerEpoch(): Long = _brokerEpoch
+
+ def state(): BrokerState = _state
+
+ class BeginControlledShutdownEvent extends EventQueue.Event {
+ override def run(): Unit = {
+ _state match {
+ case BrokerState.PENDING_CONTROLLED_SHUTDOWN =>
+ info(s"Attempted to enter controlled shutdown state, but we are already in " +
+ s"that state.")
+ case BrokerState.RUNNING =>
+ info(s"Beginning controlled shutdown.")
+ _state = BrokerState.PENDING_CONTROLLED_SHUTDOWN
+ case _ =>
+ info(s"Skipping controlled shutdown because we are in state ${_state}.")
+ beginShutdown()
+ }
+ }
+ }
+
+ /**
+ * Enter the controlled shutdown state if we are in RUNNING state.
+ * Or, if we're not running, shut down immediately.
+ */
+ def beginControlledShutdown(): Unit = {
+ eventQueue.append(new BeginControlledShutdownEvent())
+ }
+
+ /**
+ * Start shutting down the BrokerLifecycleManager, but do not block.
+ */
+ def beginShutdown(): Unit = {
+ eventQueue.beginShutdown("beginShutdown", new ShutdownEvent())
+ }
+
+ /**
+ * Shut down the BrokerLifecycleManager and block until all threads are joined.
+ */
+ def close(): Unit = {
+ beginShutdown()
+ eventQueue.close()
+ }
+
+ class SetReadyToUnfenceEvent() extends EventQueue.Event {
+ override def run(): Unit = {
+ readyToUnfence = true
+ scheduleNextCommunicationImmediately()
+ }
+ }
+
+ class StartupEvent(highestMetadataOffsetProvider: () => Long,
+ channelManager: BrokerToControllerChannelManager,
+ clusterId: Uuid,
+ advertisedListeners: ListenerCollection,
+ supportedFeatures: util.Map[String, VersionRange]) extends EventQueue.Event {
+ override def run(): Unit = {
+ _highestMetadataOffsetProvider = highestMetadataOffsetProvider
+ _channelManager = channelManager
+ _channelManager.start()
Review comment:
If this class is owning the lifecycle for `_channelManager`, should it not also instantiate it?
##########
File path: core/src/main/scala/kafka/server/BrokerLifecycleManager.scala
##########
@@ -0,0 +1,457 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package kafka.server
+
+import java.util
+import java.util.concurrent.TimeUnit.{MILLISECONDS, NANOSECONDS}
+import java.util.concurrent.{CompletableFuture, TimeUnit}
+import kafka.utils.Logging
+import org.apache.kafka.clients.ClientResponse
+import org.apache.kafka.common.Uuid
+import org.apache.kafka.common.message.BrokerRegistrationRequestData.ListenerCollection
+import org.apache.kafka.common.message.{BrokerHeartbeatRequestData, BrokerRegistrationRequestData}
+import org.apache.kafka.common.protocol.Errors
+import org.apache.kafka.common.requests.{BrokerHeartbeatRequest, BrokerHeartbeatResponse, BrokerRegistrationRequest, BrokerRegistrationResponse}
+import org.apache.kafka.metadata.{BrokerState, VersionRange}
+import org.apache.kafka.queue.EventQueue.DeadlineFunction
+import org.apache.kafka.common.utils.{ExponentialBackoff, LogContext, Time}
+import org.apache.kafka.queue.{EventQueue, KafkaEventQueue}
+import scala.jdk.CollectionConverters._
+
+
+class BrokerLifecycleManager(val config: KafkaConfig,
+ val time: Time,
+ val threadNamePrefix: Option[String]) extends Logging {
+ val logContext = new LogContext(s"[BrokerLifecycleManager id=${config.nodeId}] ")
+
+ this.logIdent = logContext.logPrefix()
+
+ /**
+ * The broker id.
+ */
+ private val nodeId = config.nodeId
+
+ /**
+ * The broker rack, or null if there is no configured rack.
+ */
+ private val rack = config.rack.orNull
+
+ /**
+ * How long to wait for registration to succeed before failing the startup process.
+ */
+ private val initialTimeoutNs = NANOSECONDS.
+ convert(config.initialRegistrationTimeoutMs.longValue(), TimeUnit.MILLISECONDS)
+
+ /**
+ * The exponential backoff to use for resending communication.
+ */
+ private val resendExponentialBackoff =
+ new ExponentialBackoff(100, 2, config.brokerSessionTimeoutMs.toLong, 0.1)
+
+ /**
+ * The number of tries we've tried to communicate.
+ */
+ private var failedAttempts = 0L
+
+ /**
+ * The broker incarnation ID. This ID uniquely identifies each time we start the broker
+ */
+ val incarnationId = Uuid.randomUuid()
+
+ /**
+ * A future which is completed just as soon as the broker has caught up with the latest
+ * metadata offset for the first time.
+ */
+ val initialCatchUpFuture = new CompletableFuture[Void]()
+
+ /**
+ * A future which is completed when controlled shutdown is done.
+ */
+ val controlledShutdownFuture = new CompletableFuture[Void]()
+
+ /**
+ * The broker epoch, or -1 if the broker has not yet registered.
+ * This variable can only be written from the event queue thread.
+ */
+ @volatile private var _brokerEpoch = -1L
+
+ /**
+ * The current broker state.
+ * This variable can only be written from the event queue thread.
+ */
+ @volatile private var _state = BrokerState.NOT_RUNNING
+
+ /**
+ * A callback function which gives this manager the current highest metadata offset.
+ * This function must be thread-safe.
+ */
+ private var _highestMetadataOffsetProvider: () => Long = null
+
+ /**
+ * True only if we are ready to unfence the broker.
+ * This variable can only be accessed from the event queue thread.
+ */
+ private var readyToUnfence = false
+
+ /**
+ * True if we sent a heartbeat to the active controller requesting controlled
+ * shutdown.
+ */
+ private var gotControlledShutdownResponse = false
+
+ /**
+ * Whether or not we this broker is registered with the controller quorum.
+ * This variable can only be accessed from the event queue thread.
+ */
+ private var registered = false
+
+ /**
+ * True if the initial registration succeeded.
+ * This variable can only be accessed from the event queue thread.
+ */
+ private var initialRegistrationSucceeded = false
+
+ /**
+ * The cluster ID, or null if this manager has not been started yet.
+ * This variable can only be accessed from the event queue thread.
+ */
+ private var _clusterId: Uuid = null
+
+ /**
+ * The listeners which this broker advertises.
+ */
+ private var _advertisedListeners: ListenerCollection = null
+
+ /**
+ * The features supported by this broker.
+ */
+ private var _supportedFeatures: util.Map[String, VersionRange] = null
+
+ /**
+ * The channel manager, or null if this manager has not been started yet.
+ * This variable can only be accessed from the event queue thread.
+ */
+ var _channelManager: BrokerToControllerChannelManager = null
+
+ /**
+ * The event queue.
+ */
+ val eventQueue = new KafkaEventQueue(time, logContext, threadNamePrefix.getOrElse(""))
+
+ /**
+ * Start the BrokerLifecycleManager.
+ *
+ * @param highestMetadataOffsetProvider Provides the current highest metadata offset.
+ * @param channelManager The brokerToControllerChannelManager to use.
+ * @param clusterId The cluster ID.
+ */
+ def start(highestMetadataOffsetProvider: () => Long,
+ channelManager: BrokerToControllerChannelManager,
+ clusterId: Uuid,
+ advertisedListeners: ListenerCollection,
+ supportedFeatures: util.Map[String, VersionRange]): Unit = {
+ eventQueue.append(new StartupEvent(highestMetadataOffsetProvider,
+ channelManager, clusterId, advertisedListeners, supportedFeatures))
+ }
+
+ def setReadyToUnfence(): Unit = {
+ eventQueue.append(new SetReadyToUnfenceEvent())
+ }
+
+ def brokerEpoch(): Long = _brokerEpoch
+
+ def state(): BrokerState = _state
+
+ class BeginControlledShutdownEvent extends EventQueue.Event {
+ override def run(): Unit = {
+ _state match {
+ case BrokerState.PENDING_CONTROLLED_SHUTDOWN =>
+ info(s"Attempted to enter controlled shutdown state, but we are already in " +
+ s"that state.")
+ case BrokerState.RUNNING =>
+ info(s"Beginning controlled shutdown.")
+ _state = BrokerState.PENDING_CONTROLLED_SHUTDOWN
+ case _ =>
+ info(s"Skipping controlled shutdown because we are in state ${_state}.")
+ beginShutdown()
+ }
+ }
+ }
+
+ /**
+ * Enter the controlled shutdown state if we are in RUNNING state.
+ * Or, if we're not running, shut down immediately.
+ */
+ def beginControlledShutdown(): Unit = {
+ eventQueue.append(new BeginControlledShutdownEvent())
+ }
+
+ /**
+ * Start shutting down the BrokerLifecycleManager, but do not block.
+ */
+ def beginShutdown(): Unit = {
+ eventQueue.beginShutdown("beginShutdown", new ShutdownEvent())
+ }
+
+ /**
+ * Shut down the BrokerLifecycleManager and block until all threads are joined.
+ */
+ def close(): Unit = {
+ beginShutdown()
+ eventQueue.close()
+ }
+
+ class SetReadyToUnfenceEvent() extends EventQueue.Event {
+ override def run(): Unit = {
+ readyToUnfence = true
+ scheduleNextCommunicationImmediately()
+ }
+ }
+
+ class StartupEvent(highestMetadataOffsetProvider: () => Long,
+ channelManager: BrokerToControllerChannelManager,
+ clusterId: Uuid,
+ advertisedListeners: ListenerCollection,
+ supportedFeatures: util.Map[String, VersionRange]) extends EventQueue.Event {
+ override def run(): Unit = {
+ _highestMetadataOffsetProvider = highestMetadataOffsetProvider
+ _channelManager = channelManager
+ _channelManager.start()
+ _state = BrokerState.STARTING
+ _clusterId = clusterId
+ _advertisedListeners = advertisedListeners
+ _supportedFeatures = supportedFeatures
+ eventQueue.scheduleDeferred("initialRegistrationTimeout",
+ new DeadlineFunction(time.nanoseconds() + initialTimeoutNs),
+ new RegistrationTimeoutEvent())
+ sendBrokerRegistration()
+ info(s"Incarnation ${incarnationId} of broker ${nodeId} in cluster ${clusterId} " +
+ "is now STARTING.")
+ }
+ }
+
+ private def sendBrokerRegistration(): Unit = {
+ val features = new BrokerRegistrationRequestData.FeatureCollection()
+ _supportedFeatures.asScala.foreach {
+ case (name, range) => features.add(new BrokerRegistrationRequestData.Feature().
+ setName(name).
+ setMinSupportedVersion(range.min()).
+ setMaxSupportedVersion(range.max()))
+ }
+ val data = new BrokerRegistrationRequestData().
+ setBrokerId(nodeId).
+ setClusterId(_clusterId).
+ setFeatures(features).
+ setIncarnationId(incarnationId).
+ setListeners(_advertisedListeners).
+ setRack(rack)
+ if (isTraceEnabled) {
+ trace(s"Sending broker registration ${data}")
+ }
+ _channelManager.sendRequest(new BrokerRegistrationRequest.Builder(data),
+ new BrokerRegistrationResponseHandler())
+ }
+
+ class BrokerRegistrationResponseHandler extends ControllerRequestCompletionHandler {
+ override def onComplete(response: ClientResponse): Unit = {
+ if (response.authenticationException() != null) {
+ error(s"Unable to register broker ${nodeId} because of an authentication exception.",
+ response.authenticationException());
+ scheduleNextCommunicationAfterFailure()
+ } else if (response.versionMismatch() != null) {
+ error(s"Unable to register broker ${nodeId} because of an API version problem.",
+ response.versionMismatch());
+ scheduleNextCommunicationAfterFailure()
+ } else if (response.responseBody() == null) {
+ warn(s"Unable to register broker ${nodeId}.")
+ scheduleNextCommunicationAfterFailure()
+ } else if (!response.responseBody().isInstanceOf[BrokerRegistrationResponse]) {
+ error(s"Unable to register broker ${nodeId} because the controller returned an " +
+ "invalid response type.")
+ scheduleNextCommunicationAfterFailure()
+ } else {
+ val message = response.responseBody().asInstanceOf[BrokerRegistrationResponse]
+ val errorCode = Errors.forCode(message.data().errorCode())
+ if (errorCode == Errors.NONE) {
+ failedAttempts = 0
+ _brokerEpoch = message.data().brokerEpoch()
+ registered = true
+ initialRegistrationSucceeded = true
+ info(s"Successfully registered broker ${nodeId} with broker epoch ${_brokerEpoch}")
+ scheduleNextCommunicationImmediately() // Immediately send a heartbeat
+ } else {
+ info(s"Unable to register broker ${nodeId} because the controller returned " +
+ s"error ${errorCode}")
+ scheduleNextCommunicationAfterFailure()
+ }
+ }
+ }
+
+ override def onTimeout(): Unit = {
+ info(s"Unable to register the broker because the RPC got timed out before it could be sent.")
+ scheduleNextCommunicationAfterFailure()
+ }
+ }
+
+ private def sendBrokerHeartbeat(): Unit = {
+ val metadataOffset = _highestMetadataOffsetProvider()
+ val data = new BrokerHeartbeatRequestData().
+ setBrokerEpoch(_brokerEpoch).
+ setBrokerId(nodeId).
+ setCurrentMetadataOffset(metadataOffset).
+ setWantFence(!readyToUnfence).
+ setWantShutDown(_state == BrokerState.PENDING_CONTROLLED_SHUTDOWN)
+ if (isTraceEnabled) {
+ trace(s"Sending broker heartbeat ${data}")
+ }
+ _channelManager.sendRequest(new BrokerHeartbeatRequest.Builder(data),
+ new BrokerHeartbeatResponseHandler())
+ }
+
+ class BrokerHeartbeatResponseHandler extends ControllerRequestCompletionHandler {
+ override def onComplete(response: ClientResponse): Unit = {
+ if (response.authenticationException() != null) {
+ error(s"Unable to send broker heartbeat for ${nodeId} because of an " +
+ "authentication exception.", response.authenticationException());
+ scheduleNextCommunicationAfterFailure()
+ } else if (response.versionMismatch() != null) {
+ error(s"Unable to send broker heartbeat for ${nodeId} because of an API " +
+ "version problem.", response.versionMismatch());
+ scheduleNextCommunicationAfterFailure()
+ } else if (response.responseBody() == null) {
+ warn(s"Unable to send broker heartbeat for ${nodeId}. Retrying.")
+ scheduleNextCommunicationAfterFailure()
+ } else if (!response.responseBody().isInstanceOf[BrokerHeartbeatResponse]) {
+ error(s"Unable to send broker heartbeat for ${nodeId} because the controller " +
+ "returned an invalid response type.")
+ scheduleNextCommunicationAfterFailure()
+ } else {
+ val message = response.responseBody().asInstanceOf[BrokerHeartbeatResponse]
+ val errorCode = Errors.forCode(message.data().errorCode())
+ if (errorCode == Errors.NONE) {
+ failedAttempts = 0
+ _state match {
+ case BrokerState.STARTING =>
+ if (message.data().isCaughtUp()) {
+ info(s"The broker has caught up. Transitioning from STARTING to RECOVERY.")
+ _state = BrokerState.RECOVERY
+ initialCatchUpFuture.complete(null)
+ } else {
+ info(s"The broker is STARTING. Still waiting to catch up with cluster metadata.")
+ }
+ // Schedule the heartbeat after only 10 ms so that in the case where
+ //there is no recovery work to be done, we start up a bit quicker.
+ scheduleNextCommunication(NANOSECONDS.convert(10, MILLISECONDS))
Review comment:
We are scheduling the next heartbeat in the near future here so we don't have to wait for the full heartbeat interval in order to make it to RUNNING. But i think this will only happen if a SetReadyToUnfenceEvent is handled between the broker entering RECOVERY and the next heartbeat request, in which case that event handler will send a heartbeat right away. If that's the case, do we really need this 10ms here or should we just wait the normal heartbeat interval?
##########
File path: core/src/main/scala/kafka/server/BrokerLifecycleManager.scala
##########
@@ -0,0 +1,457 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package kafka.server
+
+import java.util
+import java.util.concurrent.TimeUnit.{MILLISECONDS, NANOSECONDS}
+import java.util.concurrent.{CompletableFuture, TimeUnit}
+import kafka.utils.Logging
+import org.apache.kafka.clients.ClientResponse
+import org.apache.kafka.common.Uuid
+import org.apache.kafka.common.message.BrokerRegistrationRequestData.ListenerCollection
+import org.apache.kafka.common.message.{BrokerHeartbeatRequestData, BrokerRegistrationRequestData}
+import org.apache.kafka.common.protocol.Errors
+import org.apache.kafka.common.requests.{BrokerHeartbeatRequest, BrokerHeartbeatResponse, BrokerRegistrationRequest, BrokerRegistrationResponse}
+import org.apache.kafka.metadata.{BrokerState, VersionRange}
+import org.apache.kafka.queue.EventQueue.DeadlineFunction
+import org.apache.kafka.common.utils.{ExponentialBackoff, LogContext, Time}
+import org.apache.kafka.queue.{EventQueue, KafkaEventQueue}
+import scala.jdk.CollectionConverters._
+
+
+class BrokerLifecycleManager(val config: KafkaConfig,
+ val time: Time,
+ val threadNamePrefix: Option[String]) extends Logging {
+ val logContext = new LogContext(s"[BrokerLifecycleManager id=${config.nodeId}] ")
+
+ this.logIdent = logContext.logPrefix()
+
+ /**
+ * The broker id.
+ */
+ private val nodeId = config.nodeId
+
+ /**
+ * The broker rack, or null if there is no configured rack.
+ */
+ private val rack = config.rack.orNull
+
+ /**
+ * How long to wait for registration to succeed before failing the startup process.
+ */
+ private val initialTimeoutNs = NANOSECONDS.
+ convert(config.initialRegistrationTimeoutMs.longValue(), TimeUnit.MILLISECONDS)
+
+ /**
+ * The exponential backoff to use for resending communication.
+ */
+ private val resendExponentialBackoff =
+ new ExponentialBackoff(100, 2, config.brokerSessionTimeoutMs.toLong, 0.1)
+
+ /**
+ * The number of tries we've tried to communicate.
+ */
+ private var failedAttempts = 0L
+
+ /**
+ * The broker incarnation ID. This ID uniquely identifies each time we start the broker
+ */
+ val incarnationId = Uuid.randomUuid()
+
+ /**
+ * A future which is completed just as soon as the broker has caught up with the latest
+ * metadata offset for the first time.
+ */
+ val initialCatchUpFuture = new CompletableFuture[Void]()
+
+ /**
+ * A future which is completed when controlled shutdown is done.
+ */
+ val controlledShutdownFuture = new CompletableFuture[Void]()
+
+ /**
+ * The broker epoch, or -1 if the broker has not yet registered.
+ * This variable can only be written from the event queue thread.
+ */
+ @volatile private var _brokerEpoch = -1L
+
+ /**
+ * The current broker state.
+ * This variable can only be written from the event queue thread.
+ */
+ @volatile private var _state = BrokerState.NOT_RUNNING
+
+ /**
+ * A callback function which gives this manager the current highest metadata offset.
+ * This function must be thread-safe.
+ */
+ private var _highestMetadataOffsetProvider: () => Long = null
+
+ /**
+ * True only if we are ready to unfence the broker.
+ * This variable can only be accessed from the event queue thread.
+ */
+ private var readyToUnfence = false
+
+ /**
+ * True if we sent a heartbeat to the active controller requesting controlled
+ * shutdown.
+ */
+ private var gotControlledShutdownResponse = false
+
+ /**
+ * Whether or not we this broker is registered with the controller quorum.
+ * This variable can only be accessed from the event queue thread.
+ */
+ private var registered = false
+
+ /**
+ * True if the initial registration succeeded.
+ * This variable can only be accessed from the event queue thread.
+ */
+ private var initialRegistrationSucceeded = false
+
+ /**
+ * The cluster ID, or null if this manager has not been started yet.
+ * This variable can only be accessed from the event queue thread.
+ */
+ private var _clusterId: Uuid = null
+
+ /**
+ * The listeners which this broker advertises.
+ */
+ private var _advertisedListeners: ListenerCollection = null
+
+ /**
+ * The features supported by this broker.
+ */
+ private var _supportedFeatures: util.Map[String, VersionRange] = null
+
+ /**
+ * The channel manager, or null if this manager has not been started yet.
+ * This variable can only be accessed from the event queue thread.
+ */
+ var _channelManager: BrokerToControllerChannelManager = null
+
+ /**
+ * The event queue.
+ */
+ val eventQueue = new KafkaEventQueue(time, logContext, threadNamePrefix.getOrElse(""))
+
+ /**
+ * Start the BrokerLifecycleManager.
+ *
+ * @param highestMetadataOffsetProvider Provides the current highest metadata offset.
+ * @param channelManager The brokerToControllerChannelManager to use.
+ * @param clusterId The cluster ID.
+ */
+ def start(highestMetadataOffsetProvider: () => Long,
+ channelManager: BrokerToControllerChannelManager,
+ clusterId: Uuid,
+ advertisedListeners: ListenerCollection,
+ supportedFeatures: util.Map[String, VersionRange]): Unit = {
+ eventQueue.append(new StartupEvent(highestMetadataOffsetProvider,
+ channelManager, clusterId, advertisedListeners, supportedFeatures))
+ }
+
+ def setReadyToUnfence(): Unit = {
+ eventQueue.append(new SetReadyToUnfenceEvent())
+ }
+
+ def brokerEpoch(): Long = _brokerEpoch
+
+ def state(): BrokerState = _state
+
+ class BeginControlledShutdownEvent extends EventQueue.Event {
+ override def run(): Unit = {
+ _state match {
+ case BrokerState.PENDING_CONTROLLED_SHUTDOWN =>
+ info(s"Attempted to enter controlled shutdown state, but we are already in " +
+ s"that state.")
+ case BrokerState.RUNNING =>
+ info(s"Beginning controlled shutdown.")
+ _state = BrokerState.PENDING_CONTROLLED_SHUTDOWN
+ case _ =>
+ info(s"Skipping controlled shutdown because we are in state ${_state}.")
+ beginShutdown()
+ }
+ }
+ }
+
+ /**
+ * Enter the controlled shutdown state if we are in RUNNING state.
+ * Or, if we're not running, shut down immediately.
+ */
+ def beginControlledShutdown(): Unit = {
+ eventQueue.append(new BeginControlledShutdownEvent())
+ }
+
+ /**
+ * Start shutting down the BrokerLifecycleManager, but do not block.
+ */
+ def beginShutdown(): Unit = {
+ eventQueue.beginShutdown("beginShutdown", new ShutdownEvent())
+ }
+
+ /**
+ * Shut down the BrokerLifecycleManager and block until all threads are joined.
+ */
+ def close(): Unit = {
+ beginShutdown()
+ eventQueue.close()
+ }
+
+ class SetReadyToUnfenceEvent() extends EventQueue.Event {
+ override def run(): Unit = {
+ readyToUnfence = true
+ scheduleNextCommunicationImmediately()
+ }
+ }
+
+ class StartupEvent(highestMetadataOffsetProvider: () => Long,
+ channelManager: BrokerToControllerChannelManager,
+ clusterId: Uuid,
+ advertisedListeners: ListenerCollection,
+ supportedFeatures: util.Map[String, VersionRange]) extends EventQueue.Event {
+ override def run(): Unit = {
+ _highestMetadataOffsetProvider = highestMetadataOffsetProvider
+ _channelManager = channelManager
+ _channelManager.start()
+ _state = BrokerState.STARTING
+ _clusterId = clusterId
+ _advertisedListeners = advertisedListeners
+ _supportedFeatures = supportedFeatures
Review comment:
Should we be copying this map rather than assigning to it? Do we want things outside of this class to mutate the data in this map?
##########
File path: core/src/main/scala/kafka/server/BrokerLifecycleManager.scala
##########
@@ -0,0 +1,457 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package kafka.server
+
+import java.util
+import java.util.concurrent.TimeUnit.{MILLISECONDS, NANOSECONDS}
+import java.util.concurrent.{CompletableFuture, TimeUnit}
+import kafka.utils.Logging
+import org.apache.kafka.clients.ClientResponse
+import org.apache.kafka.common.Uuid
+import org.apache.kafka.common.message.BrokerRegistrationRequestData.ListenerCollection
+import org.apache.kafka.common.message.{BrokerHeartbeatRequestData, BrokerRegistrationRequestData}
+import org.apache.kafka.common.protocol.Errors
+import org.apache.kafka.common.requests.{BrokerHeartbeatRequest, BrokerHeartbeatResponse, BrokerRegistrationRequest, BrokerRegistrationResponse}
+import org.apache.kafka.metadata.{BrokerState, VersionRange}
+import org.apache.kafka.queue.EventQueue.DeadlineFunction
+import org.apache.kafka.common.utils.{ExponentialBackoff, LogContext, Time}
+import org.apache.kafka.queue.{EventQueue, KafkaEventQueue}
+import scala.jdk.CollectionConverters._
+
+
+class BrokerLifecycleManager(val config: KafkaConfig,
+ val time: Time,
+ val threadNamePrefix: Option[String]) extends Logging {
+ val logContext = new LogContext(s"[BrokerLifecycleManager id=${config.nodeId}] ")
+
+ this.logIdent = logContext.logPrefix()
+
+ /**
+ * The broker id.
+ */
+ private val nodeId = config.nodeId
+
+ /**
+ * The broker rack, or null if there is no configured rack.
+ */
+ private val rack = config.rack.orNull
+
+ /**
+ * How long to wait for registration to succeed before failing the startup process.
+ */
+ private val initialTimeoutNs = NANOSECONDS.
+ convert(config.initialRegistrationTimeoutMs.longValue(), TimeUnit.MILLISECONDS)
+
+ /**
+ * The exponential backoff to use for resending communication.
+ */
+ private val resendExponentialBackoff =
+ new ExponentialBackoff(100, 2, config.brokerSessionTimeoutMs.toLong, 0.1)
+
+ /**
+ * The number of tries we've tried to communicate.
+ */
+ private var failedAttempts = 0L
+
+ /**
+ * The broker incarnation ID. This ID uniquely identifies each time we start the broker
+ */
+ val incarnationId = Uuid.randomUuid()
+
+ /**
+ * A future which is completed just as soon as the broker has caught up with the latest
+ * metadata offset for the first time.
+ */
+ val initialCatchUpFuture = new CompletableFuture[Void]()
+
+ /**
+ * A future which is completed when controlled shutdown is done.
+ */
+ val controlledShutdownFuture = new CompletableFuture[Void]()
+
+ /**
+ * The broker epoch, or -1 if the broker has not yet registered.
+ * This variable can only be written from the event queue thread.
+ */
+ @volatile private var _brokerEpoch = -1L
+
+ /**
+ * The current broker state.
+ * This variable can only be written from the event queue thread.
+ */
+ @volatile private var _state = BrokerState.NOT_RUNNING
+
+ /**
+ * A callback function which gives this manager the current highest metadata offset.
+ * This function must be thread-safe.
+ */
+ private var _highestMetadataOffsetProvider: () => Long = null
+
+ /**
+ * True only if we are ready to unfence the broker.
+ * This variable can only be accessed from the event queue thread.
+ */
+ private var readyToUnfence = false
+
+ /**
+ * True if we sent a heartbeat to the active controller requesting controlled
+ * shutdown.
+ */
+ private var gotControlledShutdownResponse = false
+
+ /**
+ * Whether or not we this broker is registered with the controller quorum.
+ * This variable can only be accessed from the event queue thread.
+ */
+ private var registered = false
+
+ /**
+ * True if the initial registration succeeded.
+ * This variable can only be accessed from the event queue thread.
+ */
+ private var initialRegistrationSucceeded = false
+
+ /**
+ * The cluster ID, or null if this manager has not been started yet.
+ * This variable can only be accessed from the event queue thread.
+ */
+ private var _clusterId: Uuid = null
+
+ /**
+ * The listeners which this broker advertises.
+ */
+ private var _advertisedListeners: ListenerCollection = null
+
+ /**
+ * The features supported by this broker.
+ */
+ private var _supportedFeatures: util.Map[String, VersionRange] = null
+
+ /**
+ * The channel manager, or null if this manager has not been started yet.
+ * This variable can only be accessed from the event queue thread.
+ */
+ var _channelManager: BrokerToControllerChannelManager = null
+
+ /**
+ * The event queue.
+ */
+ val eventQueue = new KafkaEventQueue(time, logContext, threadNamePrefix.getOrElse(""))
+
+ /**
+ * Start the BrokerLifecycleManager.
+ *
+ * @param highestMetadataOffsetProvider Provides the current highest metadata offset.
+ * @param channelManager The brokerToControllerChannelManager to use.
+ * @param clusterId The cluster ID.
+ */
+ def start(highestMetadataOffsetProvider: () => Long,
+ channelManager: BrokerToControllerChannelManager,
+ clusterId: Uuid,
+ advertisedListeners: ListenerCollection,
+ supportedFeatures: util.Map[String, VersionRange]): Unit = {
+ eventQueue.append(new StartupEvent(highestMetadataOffsetProvider,
+ channelManager, clusterId, advertisedListeners, supportedFeatures))
+ }
+
+ def setReadyToUnfence(): Unit = {
+ eventQueue.append(new SetReadyToUnfenceEvent())
+ }
+
+ def brokerEpoch(): Long = _brokerEpoch
+
+ def state(): BrokerState = _state
+
+ class BeginControlledShutdownEvent extends EventQueue.Event {
+ override def run(): Unit = {
+ _state match {
+ case BrokerState.PENDING_CONTROLLED_SHUTDOWN =>
+ info(s"Attempted to enter controlled shutdown state, but we are already in " +
+ s"that state.")
+ case BrokerState.RUNNING =>
+ info(s"Beginning controlled shutdown.")
+ _state = BrokerState.PENDING_CONTROLLED_SHUTDOWN
+ case _ =>
+ info(s"Skipping controlled shutdown because we are in state ${_state}.")
+ beginShutdown()
+ }
+ }
+ }
+
+ /**
+ * Enter the controlled shutdown state if we are in RUNNING state.
+ * Or, if we're not running, shut down immediately.
+ */
+ def beginControlledShutdown(): Unit = {
+ eventQueue.append(new BeginControlledShutdownEvent())
+ }
+
+ /**
+ * Start shutting down the BrokerLifecycleManager, but do not block.
+ */
+ def beginShutdown(): Unit = {
+ eventQueue.beginShutdown("beginShutdown", new ShutdownEvent())
+ }
+
+ /**
+ * Shut down the BrokerLifecycleManager and block until all threads are joined.
+ */
+ def close(): Unit = {
+ beginShutdown()
+ eventQueue.close()
+ }
+
+ class SetReadyToUnfenceEvent() extends EventQueue.Event {
+ override def run(): Unit = {
+ readyToUnfence = true
+ scheduleNextCommunicationImmediately()
+ }
+ }
+
+ class StartupEvent(highestMetadataOffsetProvider: () => Long,
+ channelManager: BrokerToControllerChannelManager,
+ clusterId: Uuid,
+ advertisedListeners: ListenerCollection,
+ supportedFeatures: util.Map[String, VersionRange]) extends EventQueue.Event {
+ override def run(): Unit = {
+ _highestMetadataOffsetProvider = highestMetadataOffsetProvider
+ _channelManager = channelManager
+ _channelManager.start()
+ _state = BrokerState.STARTING
+ _clusterId = clusterId
+ _advertisedListeners = advertisedListeners
+ _supportedFeatures = supportedFeatures
+ eventQueue.scheduleDeferred("initialRegistrationTimeout",
+ new DeadlineFunction(time.nanoseconds() + initialTimeoutNs),
+ new RegistrationTimeoutEvent())
+ sendBrokerRegistration()
+ info(s"Incarnation ${incarnationId} of broker ${nodeId} in cluster ${clusterId} " +
+ "is now STARTING.")
+ }
+ }
+
+ private def sendBrokerRegistration(): Unit = {
+ val features = new BrokerRegistrationRequestData.FeatureCollection()
+ _supportedFeatures.asScala.foreach {
+ case (name, range) => features.add(new BrokerRegistrationRequestData.Feature().
+ setName(name).
+ setMinSupportedVersion(range.min()).
+ setMaxSupportedVersion(range.max()))
+ }
+ val data = new BrokerRegistrationRequestData().
+ setBrokerId(nodeId).
+ setClusterId(_clusterId).
+ setFeatures(features).
+ setIncarnationId(incarnationId).
+ setListeners(_advertisedListeners).
+ setRack(rack)
+ if (isTraceEnabled) {
+ trace(s"Sending broker registration ${data}")
+ }
+ _channelManager.sendRequest(new BrokerRegistrationRequest.Builder(data),
+ new BrokerRegistrationResponseHandler())
+ }
+
+ class BrokerRegistrationResponseHandler extends ControllerRequestCompletionHandler {
+ override def onComplete(response: ClientResponse): Unit = {
+ if (response.authenticationException() != null) {
+ error(s"Unable to register broker ${nodeId} because of an authentication exception.",
+ response.authenticationException());
+ scheduleNextCommunicationAfterFailure()
+ } else if (response.versionMismatch() != null) {
+ error(s"Unable to register broker ${nodeId} because of an API version problem.",
+ response.versionMismatch());
+ scheduleNextCommunicationAfterFailure()
+ } else if (response.responseBody() == null) {
+ warn(s"Unable to register broker ${nodeId}.")
+ scheduleNextCommunicationAfterFailure()
+ } else if (!response.responseBody().isInstanceOf[BrokerRegistrationResponse]) {
+ error(s"Unable to register broker ${nodeId} because the controller returned an " +
+ "invalid response type.")
+ scheduleNextCommunicationAfterFailure()
+ } else {
+ val message = response.responseBody().asInstanceOf[BrokerRegistrationResponse]
+ val errorCode = Errors.forCode(message.data().errorCode())
+ if (errorCode == Errors.NONE) {
+ failedAttempts = 0
+ _brokerEpoch = message.data().brokerEpoch()
+ registered = true
+ initialRegistrationSucceeded = true
+ info(s"Successfully registered broker ${nodeId} with broker epoch ${_brokerEpoch}")
+ scheduleNextCommunicationImmediately() // Immediately send a heartbeat
+ } else {
+ info(s"Unable to register broker ${nodeId} because the controller returned " +
+ s"error ${errorCode}")
+ scheduleNextCommunicationAfterFailure()
+ }
+ }
+ }
+
+ override def onTimeout(): Unit = {
+ info(s"Unable to register the broker because the RPC got timed out before it could be sent.")
+ scheduleNextCommunicationAfterFailure()
+ }
+ }
+
+ private def sendBrokerHeartbeat(): Unit = {
+ val metadataOffset = _highestMetadataOffsetProvider()
+ val data = new BrokerHeartbeatRequestData().
+ setBrokerEpoch(_brokerEpoch).
+ setBrokerId(nodeId).
+ setCurrentMetadataOffset(metadataOffset).
+ setWantFence(!readyToUnfence).
+ setWantShutDown(_state == BrokerState.PENDING_CONTROLLED_SHUTDOWN)
+ if (isTraceEnabled) {
+ trace(s"Sending broker heartbeat ${data}")
+ }
+ _channelManager.sendRequest(new BrokerHeartbeatRequest.Builder(data),
+ new BrokerHeartbeatResponseHandler())
+ }
+
+ class BrokerHeartbeatResponseHandler extends ControllerRequestCompletionHandler {
+ override def onComplete(response: ClientResponse): Unit = {
+ if (response.authenticationException() != null) {
+ error(s"Unable to send broker heartbeat for ${nodeId} because of an " +
+ "authentication exception.", response.authenticationException());
+ scheduleNextCommunicationAfterFailure()
+ } else if (response.versionMismatch() != null) {
+ error(s"Unable to send broker heartbeat for ${nodeId} because of an API " +
+ "version problem.", response.versionMismatch());
+ scheduleNextCommunicationAfterFailure()
+ } else if (response.responseBody() == null) {
+ warn(s"Unable to send broker heartbeat for ${nodeId}. Retrying.")
+ scheduleNextCommunicationAfterFailure()
+ } else if (!response.responseBody().isInstanceOf[BrokerHeartbeatResponse]) {
+ error(s"Unable to send broker heartbeat for ${nodeId} because the controller " +
+ "returned an invalid response type.")
+ scheduleNextCommunicationAfterFailure()
+ } else {
+ val message = response.responseBody().asInstanceOf[BrokerHeartbeatResponse]
+ val errorCode = Errors.forCode(message.data().errorCode())
+ if (errorCode == Errors.NONE) {
+ failedAttempts = 0
+ _state match {
+ case BrokerState.STARTING =>
+ if (message.data().isCaughtUp()) {
+ info(s"The broker has caught up. Transitioning from STARTING to RECOVERY.")
+ _state = BrokerState.RECOVERY
+ initialCatchUpFuture.complete(null)
+ } else {
+ info(s"The broker is STARTING. Still waiting to catch up with cluster metadata.")
+ }
+ // Schedule the heartbeat after only 10 ms so that in the case where
+ //there is no recovery work to be done, we start up a bit quicker.
+ scheduleNextCommunication(NANOSECONDS.convert(10, MILLISECONDS))
+ case BrokerState.RECOVERY =>
+ if (!message.data().isFenced()) {
+ info(s"The broker has been unfenced. Transitioning from RECOVERY to RUNNING.")
+ _state = BrokerState.RUNNING
+ } else {
+ info(s"The broker is in RECOVERY.")
+ }
+ scheduleNextCommunicationAfterSuccess()
+ case BrokerState.RUNNING =>
+ debug(s"The broker is RUNNING. Processing heartbeat response.")
+ scheduleNextCommunicationAfterSuccess()
+ case BrokerState.PENDING_CONTROLLED_SHUTDOWN =>
+ if (!message.data().shouldShutDown()) {
+ info(s"The broker is in PENDING_CONTROLLED_SHUTDOWN state, still waiting " +
+ "for the active controller.")
+ if (!gotControlledShutdownResponse) {
+ // If this is the first pending controlled shutdown response we got,
+ // schedule our next heartbeat a little bit sooner than we usually would.
+ // In the case where controlled shutdown completes quickly, this will
+ // speed things up a little bit.
+ scheduleNextCommunication(NANOSECONDS.convert(50, MILLISECONDS))
+ } else {
+ scheduleNextCommunicationAfterSuccess()
+ }
+ } else {
+ info(s"The controlled has asked us to exit controlled shutdown.")
+ beginShutdown()
+ }
+ gotControlledShutdownResponse = true
+ case BrokerState.SHUTTING_DOWN =>
+ info(s"The broker is SHUTTING_DOWN. Ignoring heartbeat response.")
+ case _ =>
+ error(s"Unexpected broker state ${_state}")
+ scheduleNextCommunicationAfterSuccess()
+ }
+ } else {
+ warn(s"Broker ${nodeId} sent a heartbeat request but received error ${errorCode}.")
+ scheduleNextCommunicationAfterFailure()
+ }
+ }
+ }
+
+ override def onTimeout(): Unit = {
+ info("Unable to send a heartbeat because the RPC got timed out before it could be sent.")
+ scheduleNextCommunicationAfterFailure()
+ }
+ }
+
+ private def scheduleNextCommunicationImmediately(): Unit = scheduleNextCommunication(0)
+
+ private def scheduleNextCommunicationAfterFailure(): Unit = {
+ val delayMs = resendExponentialBackoff.backoff(failedAttempts)
+ failedAttempts = failedAttempts + 1
+ scheduleNextCommunication(NANOSECONDS.convert(delayMs, MILLISECONDS))
+ }
+
+ private def scheduleNextCommunicationAfterSuccess(): Unit = {
+ scheduleNextCommunication(NANOSECONDS.convert(
+ config.brokerHeartbeatIntervalMs.longValue() , MILLISECONDS))
+ }
+
+ private def scheduleNextCommunication(intervalNs: Long): Unit = {
+ trace(s"Scheduling next communication at ${MILLISECONDS.convert(intervalNs, NANOSECONDS)} " +
+ "ms from now.")
+ val deadlineNs = time.nanoseconds() + intervalNs
+ eventQueue.scheduleDeferred("communication",
+ new DeadlineFunction(deadlineNs),
+ new CommunicationEvent())
+ }
+
+ class RegistrationTimeoutEvent extends EventQueue.Event {
+ override def run(): Unit = {
+ if (!initialRegistrationSucceeded) {
+ error("Shutting down because we were unable to register with the controller quorum.")
+ eventQueue.beginShutdown("registrationTimeout", new ShutdownEvent())
+ }
+ }
+ }
+
+ class CommunicationEvent extends EventQueue.Event {
+ override def run(): Unit = {
+ if (registered) {
+ sendBrokerHeartbeat()
+ } else {
+ sendBrokerRegistration()
+ }
+ }
+ }
+
+ class ShutdownEvent extends EventQueue.Event {
+ override def run(): Unit = {
+ info(s"Transitioning from ${_state} to ${BrokerState.SHUTTING_DOWN}.")
+ _state = BrokerState.SHUTTING_DOWN
+ controlledShutdownFuture.complete(null)
+ initialCatchUpFuture.cancel(false)
+ _channelManager.shutdown()
Review comment:
Do we need to guard against `_channelManager` being null here? Is it possible that `close` is called without `start` having been called, maybe in some faulty startup scenario?
##########
File path: core/src/main/scala/kafka/server/BrokerLifecycleManager.scala
##########
@@ -0,0 +1,457 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package kafka.server
+
+import java.util
+import java.util.concurrent.TimeUnit.{MILLISECONDS, NANOSECONDS}
+import java.util.concurrent.{CompletableFuture, TimeUnit}
+import kafka.utils.Logging
+import org.apache.kafka.clients.ClientResponse
+import org.apache.kafka.common.Uuid
+import org.apache.kafka.common.message.BrokerRegistrationRequestData.ListenerCollection
+import org.apache.kafka.common.message.{BrokerHeartbeatRequestData, BrokerRegistrationRequestData}
+import org.apache.kafka.common.protocol.Errors
+import org.apache.kafka.common.requests.{BrokerHeartbeatRequest, BrokerHeartbeatResponse, BrokerRegistrationRequest, BrokerRegistrationResponse}
+import org.apache.kafka.metadata.{BrokerState, VersionRange}
+import org.apache.kafka.queue.EventQueue.DeadlineFunction
+import org.apache.kafka.common.utils.{ExponentialBackoff, LogContext, Time}
+import org.apache.kafka.queue.{EventQueue, KafkaEventQueue}
+import scala.jdk.CollectionConverters._
+
+
+class BrokerLifecycleManager(val config: KafkaConfig,
+ val time: Time,
+ val threadNamePrefix: Option[String]) extends Logging {
+ val logContext = new LogContext(s"[BrokerLifecycleManager id=${config.nodeId}] ")
+
+ this.logIdent = logContext.logPrefix()
+
+ /**
+ * The broker id.
+ */
+ private val nodeId = config.nodeId
+
+ /**
+ * The broker rack, or null if there is no configured rack.
+ */
+ private val rack = config.rack.orNull
+
+ /**
+ * How long to wait for registration to succeed before failing the startup process.
+ */
+ private val initialTimeoutNs = NANOSECONDS.
+ convert(config.initialRegistrationTimeoutMs.longValue(), TimeUnit.MILLISECONDS)
+
+ /**
+ * The exponential backoff to use for resending communication.
+ */
+ private val resendExponentialBackoff =
+ new ExponentialBackoff(100, 2, config.brokerSessionTimeoutMs.toLong, 0.1)
+
+ /**
+ * The number of tries we've tried to communicate.
+ */
+ private var failedAttempts = 0L
+
+ /**
+ * The broker incarnation ID. This ID uniquely identifies each time we start the broker
+ */
+ val incarnationId = Uuid.randomUuid()
+
+ /**
+ * A future which is completed just as soon as the broker has caught up with the latest
+ * metadata offset for the first time.
+ */
+ val initialCatchUpFuture = new CompletableFuture[Void]()
+
+ /**
+ * A future which is completed when controlled shutdown is done.
+ */
+ val controlledShutdownFuture = new CompletableFuture[Void]()
+
+ /**
+ * The broker epoch, or -1 if the broker has not yet registered.
+ * This variable can only be written from the event queue thread.
+ */
+ @volatile private var _brokerEpoch = -1L
+
+ /**
+ * The current broker state.
+ * This variable can only be written from the event queue thread.
+ */
+ @volatile private var _state = BrokerState.NOT_RUNNING
+
+ /**
+ * A callback function which gives this manager the current highest metadata offset.
+ * This function must be thread-safe.
+ */
+ private var _highestMetadataOffsetProvider: () => Long = null
+
+ /**
+ * True only if we are ready to unfence the broker.
+ * This variable can only be accessed from the event queue thread.
+ */
+ private var readyToUnfence = false
+
+ /**
+ * True if we sent a heartbeat to the active controller requesting controlled
+ * shutdown.
+ */
+ private var gotControlledShutdownResponse = false
+
+ /**
+ * Whether or not we this broker is registered with the controller quorum.
+ * This variable can only be accessed from the event queue thread.
+ */
+ private var registered = false
+
+ /**
+ * True if the initial registration succeeded.
+ * This variable can only be accessed from the event queue thread.
+ */
+ private var initialRegistrationSucceeded = false
+
+ /**
+ * The cluster ID, or null if this manager has not been started yet.
+ * This variable can only be accessed from the event queue thread.
+ */
+ private var _clusterId: Uuid = null
+
+ /**
+ * The listeners which this broker advertises.
+ */
+ private var _advertisedListeners: ListenerCollection = null
+
+ /**
+ * The features supported by this broker.
+ */
+ private var _supportedFeatures: util.Map[String, VersionRange] = null
+
+ /**
+ * The channel manager, or null if this manager has not been started yet.
+ * This variable can only be accessed from the event queue thread.
+ */
+ var _channelManager: BrokerToControllerChannelManager = null
+
+ /**
+ * The event queue.
+ */
+ val eventQueue = new KafkaEventQueue(time, logContext, threadNamePrefix.getOrElse(""))
+
+ /**
+ * Start the BrokerLifecycleManager.
+ *
+ * @param highestMetadataOffsetProvider Provides the current highest metadata offset.
+ * @param channelManager The brokerToControllerChannelManager to use.
+ * @param clusterId The cluster ID.
+ */
+ def start(highestMetadataOffsetProvider: () => Long,
+ channelManager: BrokerToControllerChannelManager,
+ clusterId: Uuid,
+ advertisedListeners: ListenerCollection,
+ supportedFeatures: util.Map[String, VersionRange]): Unit = {
+ eventQueue.append(new StartupEvent(highestMetadataOffsetProvider,
+ channelManager, clusterId, advertisedListeners, supportedFeatures))
+ }
+
+ def setReadyToUnfence(): Unit = {
+ eventQueue.append(new SetReadyToUnfenceEvent())
+ }
+
+ def brokerEpoch(): Long = _brokerEpoch
+
+ def state(): BrokerState = _state
+
+ class BeginControlledShutdownEvent extends EventQueue.Event {
+ override def run(): Unit = {
+ _state match {
+ case BrokerState.PENDING_CONTROLLED_SHUTDOWN =>
+ info(s"Attempted to enter controlled shutdown state, but we are already in " +
+ s"that state.")
+ case BrokerState.RUNNING =>
+ info(s"Beginning controlled shutdown.")
+ _state = BrokerState.PENDING_CONTROLLED_SHUTDOWN
+ case _ =>
+ info(s"Skipping controlled shutdown because we are in state ${_state}.")
+ beginShutdown()
+ }
+ }
+ }
+
+ /**
+ * Enter the controlled shutdown state if we are in RUNNING state.
+ * Or, if we're not running, shut down immediately.
+ */
+ def beginControlledShutdown(): Unit = {
+ eventQueue.append(new BeginControlledShutdownEvent())
+ }
+
+ /**
+ * Start shutting down the BrokerLifecycleManager, but do not block.
+ */
+ def beginShutdown(): Unit = {
+ eventQueue.beginShutdown("beginShutdown", new ShutdownEvent())
+ }
+
+ /**
+ * Shut down the BrokerLifecycleManager and block until all threads are joined.
+ */
+ def close(): Unit = {
+ beginShutdown()
+ eventQueue.close()
+ }
+
+ class SetReadyToUnfenceEvent() extends EventQueue.Event {
+ override def run(): Unit = {
+ readyToUnfence = true
+ scheduleNextCommunicationImmediately()
+ }
+ }
+
+ class StartupEvent(highestMetadataOffsetProvider: () => Long,
+ channelManager: BrokerToControllerChannelManager,
+ clusterId: Uuid,
+ advertisedListeners: ListenerCollection,
+ supportedFeatures: util.Map[String, VersionRange]) extends EventQueue.Event {
+ override def run(): Unit = {
+ _highestMetadataOffsetProvider = highestMetadataOffsetProvider
+ _channelManager = channelManager
+ _channelManager.start()
+ _state = BrokerState.STARTING
+ _clusterId = clusterId
+ _advertisedListeners = advertisedListeners
+ _supportedFeatures = supportedFeatures
+ eventQueue.scheduleDeferred("initialRegistrationTimeout",
+ new DeadlineFunction(time.nanoseconds() + initialTimeoutNs),
+ new RegistrationTimeoutEvent())
+ sendBrokerRegistration()
+ info(s"Incarnation ${incarnationId} of broker ${nodeId} in cluster ${clusterId} " +
+ "is now STARTING.")
+ }
+ }
+
+ private def sendBrokerRegistration(): Unit = {
+ val features = new BrokerRegistrationRequestData.FeatureCollection()
+ _supportedFeatures.asScala.foreach {
+ case (name, range) => features.add(new BrokerRegistrationRequestData.Feature().
+ setName(name).
+ setMinSupportedVersion(range.min()).
+ setMaxSupportedVersion(range.max()))
+ }
+ val data = new BrokerRegistrationRequestData().
+ setBrokerId(nodeId).
+ setClusterId(_clusterId).
+ setFeatures(features).
+ setIncarnationId(incarnationId).
+ setListeners(_advertisedListeners).
+ setRack(rack)
+ if (isTraceEnabled) {
+ trace(s"Sending broker registration ${data}")
+ }
+ _channelManager.sendRequest(new BrokerRegistrationRequest.Builder(data),
+ new BrokerRegistrationResponseHandler())
+ }
+
+ class BrokerRegistrationResponseHandler extends ControllerRequestCompletionHandler {
+ override def onComplete(response: ClientResponse): Unit = {
+ if (response.authenticationException() != null) {
+ error(s"Unable to register broker ${nodeId} because of an authentication exception.",
+ response.authenticationException());
+ scheduleNextCommunicationAfterFailure()
+ } else if (response.versionMismatch() != null) {
+ error(s"Unable to register broker ${nodeId} because of an API version problem.",
+ response.versionMismatch());
+ scheduleNextCommunicationAfterFailure()
+ } else if (response.responseBody() == null) {
+ warn(s"Unable to register broker ${nodeId}.")
+ scheduleNextCommunicationAfterFailure()
+ } else if (!response.responseBody().isInstanceOf[BrokerRegistrationResponse]) {
+ error(s"Unable to register broker ${nodeId} because the controller returned an " +
+ "invalid response type.")
+ scheduleNextCommunicationAfterFailure()
+ } else {
+ val message = response.responseBody().asInstanceOf[BrokerRegistrationResponse]
+ val errorCode = Errors.forCode(message.data().errorCode())
+ if (errorCode == Errors.NONE) {
+ failedAttempts = 0
+ _brokerEpoch = message.data().brokerEpoch()
+ registered = true
+ initialRegistrationSucceeded = true
+ info(s"Successfully registered broker ${nodeId} with broker epoch ${_brokerEpoch}")
+ scheduleNextCommunicationImmediately() // Immediately send a heartbeat
+ } else {
+ info(s"Unable to register broker ${nodeId} because the controller returned " +
+ s"error ${errorCode}")
+ scheduleNextCommunicationAfterFailure()
+ }
+ }
+ }
+
+ override def onTimeout(): Unit = {
+ info(s"Unable to register the broker because the RPC got timed out before it could be sent.")
+ scheduleNextCommunicationAfterFailure()
+ }
+ }
+
+ private def sendBrokerHeartbeat(): Unit = {
+ val metadataOffset = _highestMetadataOffsetProvider()
+ val data = new BrokerHeartbeatRequestData().
+ setBrokerEpoch(_brokerEpoch).
+ setBrokerId(nodeId).
+ setCurrentMetadataOffset(metadataOffset).
+ setWantFence(!readyToUnfence).
+ setWantShutDown(_state == BrokerState.PENDING_CONTROLLED_SHUTDOWN)
+ if (isTraceEnabled) {
+ trace(s"Sending broker heartbeat ${data}")
+ }
+ _channelManager.sendRequest(new BrokerHeartbeatRequest.Builder(data),
+ new BrokerHeartbeatResponseHandler())
+ }
+
+ class BrokerHeartbeatResponseHandler extends ControllerRequestCompletionHandler {
+ override def onComplete(response: ClientResponse): Unit = {
+ if (response.authenticationException() != null) {
+ error(s"Unable to send broker heartbeat for ${nodeId} because of an " +
+ "authentication exception.", response.authenticationException());
+ scheduleNextCommunicationAfterFailure()
+ } else if (response.versionMismatch() != null) {
+ error(s"Unable to send broker heartbeat for ${nodeId} because of an API " +
+ "version problem.", response.versionMismatch());
+ scheduleNextCommunicationAfterFailure()
+ } else if (response.responseBody() == null) {
+ warn(s"Unable to send broker heartbeat for ${nodeId}. Retrying.")
+ scheduleNextCommunicationAfterFailure()
+ } else if (!response.responseBody().isInstanceOf[BrokerHeartbeatResponse]) {
+ error(s"Unable to send broker heartbeat for ${nodeId} because the controller " +
+ "returned an invalid response type.")
+ scheduleNextCommunicationAfterFailure()
+ } else {
+ val message = response.responseBody().asInstanceOf[BrokerHeartbeatResponse]
+ val errorCode = Errors.forCode(message.data().errorCode())
+ if (errorCode == Errors.NONE) {
+ failedAttempts = 0
+ _state match {
+ case BrokerState.STARTING =>
+ if (message.data().isCaughtUp()) {
+ info(s"The broker has caught up. Transitioning from STARTING to RECOVERY.")
+ _state = BrokerState.RECOVERY
+ initialCatchUpFuture.complete(null)
+ } else {
+ info(s"The broker is STARTING. Still waiting to catch up with cluster metadata.")
+ }
+ // Schedule the heartbeat after only 10 ms so that in the case where
+ //there is no recovery work to be done, we start up a bit quicker.
+ scheduleNextCommunication(NANOSECONDS.convert(10, MILLISECONDS))
+ case BrokerState.RECOVERY =>
+ if (!message.data().isFenced()) {
+ info(s"The broker has been unfenced. Transitioning from RECOVERY to RUNNING.")
+ _state = BrokerState.RUNNING
+ } else {
+ info(s"The broker is in RECOVERY.")
+ }
+ scheduleNextCommunicationAfterSuccess()
+ case BrokerState.RUNNING =>
+ debug(s"The broker is RUNNING. Processing heartbeat response.")
+ scheduleNextCommunicationAfterSuccess()
+ case BrokerState.PENDING_CONTROLLED_SHUTDOWN =>
+ if (!message.data().shouldShutDown()) {
+ info(s"The broker is in PENDING_CONTROLLED_SHUTDOWN state, still waiting " +
+ "for the active controller.")
+ if (!gotControlledShutdownResponse) {
+ // If this is the first pending controlled shutdown response we got,
+ // schedule our next heartbeat a little bit sooner than we usually would.
+ // In the case where controlled shutdown completes quickly, this will
+ // speed things up a little bit.
+ scheduleNextCommunication(NANOSECONDS.convert(50, MILLISECONDS))
Review comment:
Since the heartbeat interval is configurable, maybe we should calculate this from the interval instead of a fixed value. Maybe something like (interval / 2) or sqrt(interval)?
##########
File path: core/src/main/scala/kafka/server/BrokerLifecycleManager.scala
##########
@@ -0,0 +1,457 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package kafka.server
+
+import java.util
+import java.util.concurrent.TimeUnit.{MILLISECONDS, NANOSECONDS}
+import java.util.concurrent.{CompletableFuture, TimeUnit}
+import kafka.utils.Logging
+import org.apache.kafka.clients.ClientResponse
+import org.apache.kafka.common.Uuid
+import org.apache.kafka.common.message.BrokerRegistrationRequestData.ListenerCollection
+import org.apache.kafka.common.message.{BrokerHeartbeatRequestData, BrokerRegistrationRequestData}
+import org.apache.kafka.common.protocol.Errors
+import org.apache.kafka.common.requests.{BrokerHeartbeatRequest, BrokerHeartbeatResponse, BrokerRegistrationRequest, BrokerRegistrationResponse}
+import org.apache.kafka.metadata.{BrokerState, VersionRange}
+import org.apache.kafka.queue.EventQueue.DeadlineFunction
+import org.apache.kafka.common.utils.{ExponentialBackoff, LogContext, Time}
+import org.apache.kafka.queue.{EventQueue, KafkaEventQueue}
+import scala.jdk.CollectionConverters._
+
+
+class BrokerLifecycleManager(val config: KafkaConfig,
+ val time: Time,
+ val threadNamePrefix: Option[String]) extends Logging {
+ val logContext = new LogContext(s"[BrokerLifecycleManager id=${config.nodeId}] ")
+
+ this.logIdent = logContext.logPrefix()
+
+ /**
+ * The broker id.
+ */
+ private val nodeId = config.nodeId
+
+ /**
+ * The broker rack, or null if there is no configured rack.
+ */
+ private val rack = config.rack.orNull
+
+ /**
+ * How long to wait for registration to succeed before failing the startup process.
+ */
+ private val initialTimeoutNs = NANOSECONDS.
+ convert(config.initialRegistrationTimeoutMs.longValue(), TimeUnit.MILLISECONDS)
+
+ /**
+ * The exponential backoff to use for resending communication.
+ */
+ private val resendExponentialBackoff =
+ new ExponentialBackoff(100, 2, config.brokerSessionTimeoutMs.toLong, 0.1)
+
+ /**
+ * The number of tries we've tried to communicate.
+ */
+ private var failedAttempts = 0L
+
+ /**
+ * The broker incarnation ID. This ID uniquely identifies each time we start the broker
+ */
+ val incarnationId = Uuid.randomUuid()
+
+ /**
+ * A future which is completed just as soon as the broker has caught up with the latest
+ * metadata offset for the first time.
+ */
+ val initialCatchUpFuture = new CompletableFuture[Void]()
+
+ /**
+ * A future which is completed when controlled shutdown is done.
+ */
+ val controlledShutdownFuture = new CompletableFuture[Void]()
+
+ /**
+ * The broker epoch, or -1 if the broker has not yet registered.
+ * This variable can only be written from the event queue thread.
+ */
+ @volatile private var _brokerEpoch = -1L
+
+ /**
+ * The current broker state.
+ * This variable can only be written from the event queue thread.
+ */
+ @volatile private var _state = BrokerState.NOT_RUNNING
+
+ /**
+ * A callback function which gives this manager the current highest metadata offset.
+ * This function must be thread-safe.
+ */
+ private var _highestMetadataOffsetProvider: () => Long = null
+
+ /**
+ * True only if we are ready to unfence the broker.
+ * This variable can only be accessed from the event queue thread.
+ */
+ private var readyToUnfence = false
+
+ /**
+ * True if we sent a heartbeat to the active controller requesting controlled
+ * shutdown.
+ */
+ private var gotControlledShutdownResponse = false
+
+ /**
+ * Whether or not we this broker is registered with the controller quorum.
+ * This variable can only be accessed from the event queue thread.
+ */
+ private var registered = false
+
+ /**
+ * True if the initial registration succeeded.
+ * This variable can only be accessed from the event queue thread.
+ */
+ private var initialRegistrationSucceeded = false
+
+ /**
+ * The cluster ID, or null if this manager has not been started yet.
+ * This variable can only be accessed from the event queue thread.
+ */
+ private var _clusterId: Uuid = null
+
+ /**
+ * The listeners which this broker advertises.
+ */
+ private var _advertisedListeners: ListenerCollection = null
Review comment:
nit: I think scala prefers the underscore initializer for cases like this. E.g.,
```scala
private var _advertisedListeners: ListenerCollection = _
```
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