kafka管控推荐使用 滴滴开源 Kafka运维管控平台 更符合国人的操作习惯 ,

更强大的管控能力 ,更高效的问题定位能力更便捷的集群运维能力更专业的资源治理更友好的运维生态

脚本参数

sh bin/kafka-topic -help 查看更具体参数

下面只是列出了跟 --alter 相关的参数

参数 描述 例子
--bootstrap-server 指定kafka服务 指定连接到的kafka服务; 如果有这个参数,则 --zookeeper可以不需要 –bootstrap-server localhost:9092
--replica-assignment 副本分区分配方式;修改topic的时候可以自己指定副本分配情况; --replica-assignment id0:id1:id2,id3:id4:id5,id6:id7:id8 ;其中,“id0:id1:id2,id3:id4:id5,id6:id7:id8”表示Topic TopicName一共有3个Partition(以“,”分隔),每个Partition均有3个Replica(以“:”分隔),Topic Partition Replica与Kafka Broker之间的对应关系如下:1278
--topic
--partitions 扩展到新的分区数

Alert Topic脚本

分区扩容

zk方式(不推荐)

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bin/kafka-topics.sh --zookeeper localhost:2181 --alter --topic topic1 --partitions 2

kafka版本 >= 2.2 支持下面方式(推荐)
单个Topic扩容

bin/kafka-topics.sh --bootstrap-server broker_host:port --alter --topic test_create_topic1 --partitions 4

批量扩容 (将所有正则表达式匹配到的Topic分区扩容到4个)

sh bin/kafka-topics.sh --topic ".*?" --bootstrap-server 172.23.248.85:9092 --alter --partitions 4

".*?" 正则表达式的意思是匹配所有; 您可按需匹配

PS: 当某个Topic的分区少于指定的分区数时候,他会抛出异常;但是不会影响其他Topic正常进行;


相关可选参数

参数 描述 例子
--replica-assignment 副本分区分配方式;创建topic的时候可以自己指定副本分配情况; --replica-assignment BrokerId-0:BrokerId-1:BrokerId-2,BrokerId-1:BrokerId-2:BrokerId-0,BrokerId-2:BrokerId-1:BrokerId-0 ; 这个意思是有三个分区和三个副本,对应分配的Broker; 逗号隔开标识分区;冒号隔开表示副本

PS: 虽然这里配置的是全部的分区副本分配配置,但是真正生效的是新增的分区;
比如: 以前3分区1副本是这样的

Broker-1 Broker-2 Broker-3 Broker-4
0 1 2

现在新增一个分区,--replica-assignment 2,1,3,4 ; 看这个意思好像是把0,1号分区互相换个Broker

Broker-1 Broker-2 Broker-3 Broker-4
1 0 2 3

但是实际上不会这样做,Controller在处理的时候会把前面3个截掉; 只取新增的分区分配方式,原来的还是不会变

Broker-1 Broker-2 Broker-3 Broker-4
0 1 2 3

源码解析

如果觉得源码解析过程比较枯燥乏味,可以直接如果 源码总结及其后面部分

因为在 【kafka源码】TopicCommand之创建Topic源码解析 里面分析的比较详细; 故本文就着重点分析了;

1. TopicCommand.alterTopic

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override def alterTopic(opts: TopicCommandOptions): Unit = {
val topic = new CommandTopicPartition(opts)
val topics = getTopics(opts.topic, opts.excludeInternalTopics)
//校验Topic是否存在
ensureTopicExists(topics, opts.topic)
//获取一下该topic的一些基本信息
val topicsInfo = adminClient.describeTopics(topics.asJavaCollection).values()
adminClient.createPartitions(topics.map {topicName =>
//判断是否有参数 replica-assignment 指定分区分配方式
if (topic.hasReplicaAssignment) {
val startPartitionId = topicsInfo.get(topicName).get().partitions().size()
val newAssignment = {
val replicaMap = topic.replicaAssignment.get.drop(startPartitionId)
new util.ArrayList(replicaMap.map(p => p._2.asJava).asJavaCollection).asInstanceOf[util.List[util.List[Integer]]]
}
topicName -> NewPartitions.increaseTo(topic.partitions.get, newAssignment)
} else {

topicName -> NewPartitions.increaseTo(topic.partitions.get)
}}.toMap.asJava).all().get()
}
  1. 校验Topic是否存在
  2. 如果设置了--replica-assignment 参数, 则会算出新增的分区数的分配; 这个并不会修改原本已经分配好的分区结构.从源码就可以看出来,假如我之前的分配方式是3,3,3(3分区一个副本都在BrokerId-3上)现在我传入的参数是: 3,3,3,3(多出来一个分区),这个时候会把原有的给截取掉;只传入3,(表示在Broker3新增一个分区)7652
  3. 如果没有传入参数--replica-assignment,则后面会用默认分配策略分配

客户端发起请求createPartitions

KafkaAdminClient.createPartitions 省略部分代码

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 @Override
public CreatePartitionsResult createPartitions(Map<String, NewPartitions> newPartitions,
final CreatePartitionsOptions options) {
final Map<String, KafkaFutureImpl<Void>> futures = new HashMap<>(newPartitions.size());
for (String topic : newPartitions.keySet()) {
futures.put(topic, new KafkaFutureImpl<>());
}
runnable.call(new Call("createPartitions", calcDeadlineMs(now, options.timeoutMs()),
new ControllerNodeProvider()) {
//省略部分代码
@Override
void handleFailure(Throwable throwable) {
completeAllExceptionally(futures.values(), throwable);
}
}, now);
return new CreatePartitionsResult(new HashMap<>(futures));
}
  1. 从源码中可以看到向ControllerNodeProvider 发起来createPartitions请求

2. Controller角色的服务端接受createPartitions请求处理逻辑

KafkaApis.handleCreatePartitionsRequest

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def handleCreatePartitionsRequest(request: RequestChannel.Request): Unit = {
val createPartitionsRequest = request.body[CreatePartitionsRequest]

//部分代码省略..

//如果当前不是Controller角色直接抛出异常
if (!controller.isActive) {
val result = createPartitionsRequest.data.topics.asScala.map { topic =>
(topic.name, new ApiError(Errors.NOT_CONTROLLER, null))
}.toMap
sendResponseCallback(result)
} else {
// Special handling to add duplicate topics to the response
val topics = createPartitionsRequest.data.topics.asScala
val dupes = topics.groupBy(_.name)
.filter { _._2.size > 1 }
.keySet
val notDuped = topics.filterNot(topic => dupes.contains(topic.name))
val authorizedTopics = filterAuthorized(request, ALTER, TOPIC, notDuped.map(_.name))
val (authorized, unauthorized) = notDuped.partition { topic => authorizedTopics.contains(topic.name) }

val (queuedForDeletion, valid) = authorized.partition { topic =>
controller.topicDeletionManager.isTopicQueuedUpForDeletion(topic.name)
}

val errors = dupes.map(_ -> new ApiError(Errors.INVALID_REQUEST, "Duplicate topic in request.")) ++
unauthorized.map(_.name -> new ApiError(Errors.TOPIC_AUTHORIZATION_FAILED, "The topic authorization is failed.")) ++
queuedForDeletion.map(_.name -> new ApiError(Errors.INVALID_TOPIC_EXCEPTION, "The topic is queued for deletion."))

adminManager.createPartitions(createPartitionsRequest.data.timeoutMs,
valid,
createPartitionsRequest.data.validateOnly,
request.context.listenerName, result => sendResponseCallback(result ++ errors))
}
}

  1. 检验自身是不是Controller角色,不是的话就抛出异常终止流程

  2. 鉴权

  3. 调用 adminManager.createPartitions
    3.1 从zk中获取/brokers/ids/Brokers列表的元信息的
    3.2 从zk获取/brokers/topics/{topicName}已经存在的副本分配方式,并判断是否有正在进行副本重分配的进程在执行,如果有的话就抛出异常结束流程
    3.3 如果从zk获取/brokers/topics/{topicName}数据不存在则抛出异常 The topic '$topic' does not exist
    3.4 检查修改的分区数是否比原来的分区数大,如果比原来还小或者等于原来分区数则抛出异常结束流程
    3.5 如果传入的参数--replica-assignment 中有不存在的BrokerId;则抛出异常Unknown broker(s) in replica assignment结束流程
    3.5 如果传入的--partitions数量 与--replica-assignment中新增的部分数量不匹配则抛出异常Increasing the number of partitions by... 结束流程
    3.6 调用 adminZkClient.addPartitions

adminZkClient.addPartitions 添加分区

  1. 校验--partitions数量是否比存在的分区数大,否则异常The number of partitions for a topic can only be increased
  2. 如果传入了--replica-assignment ,则对副本进行一些简单的校验
  3. 调用AdminUtils.assignReplicasToBrokers分配副本 ; 这个我们在【kafka源码】TopicCommand之创建Topic源码解析 也分析过; 具体请看【kafka源码】创建Topic的时候是如何分区和副本的分配规则; 当然这里由于我们是新增的分区,只会将新增的分区进行分配计算
  4. 得到分配规则只后,调用adminZkClient.writeTopicPartitionAssignment 写入

adminZkClient.writeTopicPartitionAssignment将分区信息写入zk中

在这里插入图片描述

我们在 【kafka源码】TopicCommand之创建Topic源码解析的时候也分析过这段代码,但是那个时候调用的是zkClient.createTopicAssignment 创建接口
这里我们是调用 zkClient.setTopicAssignment 写入接口, 写入当然会覆盖掉原有的信息,所以写入的时候会把原来分区信息获取到,重新写入;

  1. 获取Topic原有分区副本分配信息
  2. 将原有的和现在要添加的组装成一个数据对象写入到zk节点/brokers/topics/{topicName}

3. Controller监控节点/brokers/topics/{topicName} ,真正在Broker上将分区写入磁盘

监听到节点信息变更之后调用下面的接口;
KafkaController.processPartitionModifications

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private def processPartitionModifications(topic: String): Unit = {
def restorePartitionReplicaAssignment(
topic: String,
newPartitionReplicaAssignment: Map[TopicPartition, ReplicaAssignment]
): Unit = {
info("Restoring the partition replica assignment for topic %s".format(topic))

val existingPartitions = zkClient.getChildren(TopicPartitionsZNode.path(topic))
val existingPartitionReplicaAssignment = newPartitionReplicaAssignment
.filter(p => existingPartitions.contains(p._1.partition.toString))
.map { case (tp, _) =>
tp -> controllerContext.partitionFullReplicaAssignment(tp)
}.toMap

zkClient.setTopicAssignment(topic,
existingPartitionReplicaAssignment,
controllerContext.epochZkVersion)
}

if (!isActive) return
val partitionReplicaAssignment = zkClient.getFullReplicaAssignmentForTopics(immutable.Set(topic))
val partitionsToBeAdded = partitionReplicaAssignment.filter { case (topicPartition, _) =>
controllerContext.partitionReplicaAssignment(topicPartition).isEmpty
}

if (topicDeletionManager.isTopicQueuedUpForDeletion(topic)) {
if (partitionsToBeAdded.nonEmpty) {
warn("Skipping adding partitions %s for topic %s since it is currently being deleted"
.format(partitionsToBeAdded.map(_._1.partition).mkString(","), topic))

restorePartitionReplicaAssignment(topic, partitionReplicaAssignment)
} else {
// This can happen if existing partition replica assignment are restored to prevent increasing partition count during topic deletion
info("Ignoring partition change during topic deletion as no new partitions are added")
}
} else if (partitionsToBeAdded.nonEmpty) {
info(s"New partitions to be added $partitionsToBeAdded")
partitionsToBeAdded.foreach { case (topicPartition, assignedReplicas) =>
controllerContext.updatePartitionFullReplicaAssignment(topicPartition, assignedReplicas)
}
onNewPartitionCreation(partitionsToBeAdded.keySet)
}
}

  1. 判断是否Controller,不是则直接结束流程
  2. 获取/brokers/topics/{topicName} 节点信息, 然后再对比一下当前该节点的分区分配信息; 看看有没有是新增的分区; 如果是新增的分区这个时候是还没有/brokers/topics/{topicName}/partitions/{分区号}/state ;
  3. 如果当前的TOPIC正在被删除中,那么就没有必要执行扩分区了
  4. 将新增加的分区信息加载到内存中
  5. 调用接口KafkaController.onNewPartitionCreation

KafkaController.onNewPartitionCreation 新增分区

从这里开始 , 后面的流程就跟创建Topic的对应流程一样了;

该接口主要是针对新增分区和副本的一些状态流转过程; 在【kafka源码】TopicCommand之创建Topic源码解析 也同样分析过

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/**
* This callback is invoked by the topic change callback with the list of failed brokers as input.
* It does the following -
* 1. Move the newly created partitions to the NewPartition state
* 2. Move the newly created partitions from NewPartition->OnlinePartition state
*/
private def onNewPartitionCreation(newPartitions: Set[TopicPartition]): Unit = {
info(s"New partition creation callback for ${newPartitions.mkString(",")}")
partitionStateMachine.handleStateChanges(newPartitions.toSeq, NewPartition)
replicaStateMachine.handleStateChanges(controllerContext.replicasForPartition(newPartitions).toSeq, NewReplica)
partitionStateMachine.handleStateChanges(
newPartitions.toSeq,
OnlinePartition,
Some(OfflinePartitionLeaderElectionStrategy(false))
)
replicaStateMachine.handleStateChanges(controllerContext.replicasForPartition(newPartitions).toSeq, OnlineReplica)
}
  1. 将待创建的分区状态流转为NewPartition; 在这里插入图片描述
  2. 将待创建的副本 状态流转为NewReplica;在这里插入图片描述
  3. 将分区状态从刚刚的NewPartition流转为OnlinePartition
  4. 获取leaderIsrAndControllerEpochs; Leader为副本的第一个;
    1. 向zk中写入/brokers/topics/{topicName}/partitions/ 持久节点; 无数据
    2. 向zk中写入/brokers/topics/{topicName}/partitions/{分区号} 持久节点; 无数据
    3. 向zk中写入/brokers/topics/{topicName}/partitions/{分区号}/state 持久节点; 数据为leaderIsrAndControllerEpoch在这里插入图片描述
    1. 向副本所属Broker发送leaderAndIsrRequest请求
    2. 向所有Broker发送UPDATE_METADATA 请求
  5. 将副本状态从刚刚的NewReplica流转为OnlineReplica ,更新下内存

关于分区状态机和副本状态机详情请看【kafka源码】Controller中的状态机

4. Broker收到LeaderAndIsrRequest 创建本地Log

上面步骤中有说到向副本所属Broker发送leaderAndIsrRequest请求,那么这里做了什么呢
其实主要做的是 创建本地Log

代码太多,这里我们直接定位到只跟创建Topic相关的关键代码来分析
KafkaApis.handleLeaderAndIsrRequest->replicaManager.becomeLeaderOrFollower->ReplicaManager.makeLeaders...LogManager.getOrCreateLog

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/**
* 如果日志已经存在,只返回现有日志的副本否则如果 isNew=true 或者如果没有离线日志目录,则为给定的主题和给定的分区创建日志 否则抛出 KafkaStorageException
*/
def getOrCreateLog(topicPartition: TopicPartition, config: LogConfig, isNew: Boolean = false, isFuture: Boolean = false): Log = {
logCreationOrDeletionLock synchronized {
getLog(topicPartition, isFuture).getOrElse {
// create the log if it has not already been created in another thread
if (!isNew && offlineLogDirs.nonEmpty)
throw new KafkaStorageException(s"Can not create log for $topicPartition because log directories ${offlineLogDirs.mkString(",")} are offline")

val logDirs: List[File] = {
val preferredLogDir = preferredLogDirs.get(topicPartition)

if (isFuture) {
if (preferredLogDir == null)
throw new IllegalStateException(s"Can not create the future log for $topicPartition without having a preferred log directory")
else if (getLog(topicPartition).get.dir.getParent == preferredLogDir)
throw new IllegalStateException(s"Can not create the future log for $topicPartition in the current log directory of this partition")
}

if (preferredLogDir != null)
List(new File(preferredLogDir))
else
nextLogDirs()
}

val logDirName = {
if (isFuture)
Log.logFutureDirName(topicPartition)
else
Log.logDirName(topicPartition)
}

val logDir = logDirs
.toStream // to prevent actually mapping the whole list, lazy map
.map(createLogDirectory(_, logDirName))
.find(_.isSuccess)
.getOrElse(Failure(new KafkaStorageException("No log directories available. Tried " + logDirs.map(_.getAbsolutePath).mkString(", "))))
.get // If Failure, will throw

val log = Log(
dir = logDir,
config = config,
logStartOffset = 0L,
recoveryPoint = 0L,
maxProducerIdExpirationMs = maxPidExpirationMs,
producerIdExpirationCheckIntervalMs = LogManager.ProducerIdExpirationCheckIntervalMs,
scheduler = scheduler,
time = time,
brokerTopicStats = brokerTopicStats,
logDirFailureChannel = logDirFailureChannel)

if (isFuture)
futureLogs.put(topicPartition, log)
else
currentLogs.put(topicPartition, log)

info(s"Created log for partition $topicPartition in $logDir with properties " + s"{${config.originals.asScala.mkString(", ")}}.")
// Remove the preferred log dir since it has already been satisfied
preferredLogDirs.remove(topicPartition)

log
}
}
}
  1. 如果日志已经存在,只返回现有日志的副本否则如果 isNew=true 或者如果没有离线日志目录,则为给定的主题和给定的分区创建日志 否则抛出 KafkaStorageException

详细请看 【kafka源码】LeaderAndIsrRequest请求

源码总结

看图说话

在这里插入图片描述

Q&A

如果自定义的分配Broker不存在会怎么样

会抛出异常Unknown broker(s) in replica assignment, 因为在执行的时候会去zk获取当前的在线Broker列表,然后判断是否在线;

如果设置的分区数不等于 --replica-assignment中新增的数目会怎么样

会抛出异常Increasing the number of partitions by..结束流程

如果写入/brokers/topics/{topicName}之后 Controller监听到请求正好挂掉怎么办

Controller挂掉会发生重新选举,选举成功之后, 检查到/brokers/topics/{topicName}之后发现没有生成对应的分区,会自动执行接下来的流程;

如果我手动在zk中写入节点/brokers/topics/{topicName}/partitions/{分区号}/state 会怎么样

Controller并没有监听这个节点,所以不会有变化; 但是当Controller发生重新选举的时候,
被删除的节点会被重新添加回来;
但是写入的节点 就不会被删除了;写入的节点信息会被保存在Controller内存中;
同样这会影响到分区扩容


例子🌰:
当前分区3个,副本一个,手贱在zk上添加了一个节点如下图:

在这里插入图片描述

这个时候我想扩展一个分区; 然后执行了脚本, 虽然/brokers/topics/test_create_topic3节点数据变; 但是Broker真正在LeaderAndIsrRequest请求里面没有执行创建本地Log文件; 这是因为源码读取到zk下面partitions的节点数量和新增之后的节点数量没有变更,那么它就认为本次请求没有变更就不会执行创建本地Log文件了;
如果判断有变更,还是会去创建的;
手贱zk写入N个partition节点 + 扩充N个分区 = Log文件不会被创建
手贱zk写入N个partition节点 + 扩充>N个分区 = 正常扩容

如果直接修改节点/brokers/topics/{topicName}中的配置会怎么样

如果该节点信息是{"version":2,"partitions":{"2":[1],"1":[1],"0":[1]},"adding_replicas":{},"removing_replicas":{}} 看数据,说明3个分区1个副本都在Broker-1上;
我在zk上修改成{"version":2,"partitions":{"2":[2],"1":[1],"0":[0]},"adding_replicas":{},"removing_replicas":{}}
想将分区分配到 Broker-0,Broker-1,Broker-2上
TODO。。。