1· 概述
1.1 kafka是什么
在流式计算中，Kafka一般用来缓存数据，Storm通过消费Kafka的数据进行计算。
1）Apache Kafka是一个开源消息系统，由Scala写成。是由Apache软件基金会开发的一个开源消息系统项目。
2）Kafka最初是由LinkedIn开发，并于2011年初开源。2012年10月从Apache Incubator毕业。该项目的目标是为处理实时数据提供一个统一、高通量、低等待的平台。
3）Kafka是一个分布式消息队列。Kafka对消息保存时根据Topic进行归类，发送消息者称为Producer，消息接受者称为Consumer，此外kafka集群有多个kafka实例组成，每个实例(server)成为broker。
4）无论是kafka集群，还是producer和consumer都依赖于zookeeper集群保存一些meta信息，来保证系统可用性。
1.2 kafka架构
本文非科普，欲知详情，请移步aoache官网。
2 安装部署
2.1 环境准备
kafka是java 编写的所有需要JDK环境，使用zookeeper存储配置，故，zookeeper.也需要安装，这2个安装都比较简单，各位同学，应该都会，此处略去安装过程，如果不会请@我。
2.2 kafka安装配置
2.2.1 下载
下载请到http://kafka.apache.org/downloads，
我们使用的是linux版本，需要下载tar包，我下载的是 kafka_2.11-2.1.0.tgz,使用SSH工具上传到阿里云服务器
2.2.2 解压安装
// 解压kafka_2.11-2.1.0.tgz
tar -zxvf kafka_2.11-2.1.0.tgz
//重命名
mv kafka_2.11-2.1.0 kafka
// 移动到安装目录
cp -r kafka /usr
2.2.3 更改配置文件
kafka 依赖于zookeepr 基本只需要更改zookeeper的配置即可，此外还需要一个存放日志的目录
创建日志存储目录
mkdir /usr/kafka/logkafka的配置文件位于安装目录下的config目录，进入到该目录查看文件内容
更改zk的配置链接地址
更改日志的存储路径
完整的配置文件如下
# 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.
# see kafka.server.KafkaConfig for additional details and defaults
############################# Server Basics #############################
# The id of the broker. This must be set to a unique integer for each broker.
broker.id=0
############################# Socket Server Settings #############################
# The address the socket server listens on. It will get the value returned from
# java.net.InetAddress.getCanonicalHostName() if not configured.
# FORMAT:
# listeners = listener_name://host_name:port
# EXAMPLE:
# listeners = PLAINTEXT://your.host.name:9092
#listeners=PLAINTEXT://:9092
# Hostname and port the broker will advertise to producers and consumers. If not set,
# it uses the value for "listeners" if configured. Otherwise, it will use the value
# returned from java.net.InetAddress.getCanonicalHostName().
#advertised.listeners=PLAINTEXT://your.host.name:9092
# Maps listener names to security protocols, the default is for them to be the same. See the config documentation for more details
#listener.security.protocol.map=PLAINTEXT:PLAINTEXT,SSL:SSL,SASL_PLAINTEXT:SASL_PLAINTEXT,SASL_SSL:SASL_SSL
# The number of threads that the server uses for receiving requests from the network and sending responses to the network
num.network.threads=3
# The number of threads that the server uses for processing requests, which may include disk I/O
num.io.threads=8
# The send buffer (SO_SNDBUF) used by the socket server
socket.send.buffer.bytes=102400
# The receive buffer (SO_RCVBUF) used by the socket server
socket.receive.buffer.bytes=102400
# The maximum size of a request that the socket server will accept (protection against OOM)
socket.request.max.bytes=104857600
############################# Log Basics #############################
# A comma separated list of directories under which to store log files
log.dirs=/usr/kafka/log
# The default number of log partitions per topic. More partitions allow greater
# parallelism for consumption, but this will also result in more files across
# the brokers.
num.partitions=1
# The number of threads per data directory to be used for log recovery at startup and flushing at shutdown.
# This value is recommended to be increased for installations with data dirs located in RAID array.
num.recovery.threads.per.data.dir=1
############################# Internal Topic Settings #############################
# The replication factor for the group metadata internal topics "__consumer_offsets" and "__transaction_state"
# For anything other than development testing, a value greater than 1 is recommended for to ensure availability such as 3.
offsets.topic.replication.factor=1
transaction.state.log.replication.factor=1
transaction.state.log.min.isr=1
############################# Log Flush Policy #############################
# Messages are immediately written to the filesystem but by default we only fsync() to sync
# the OS cache lazily. The following configurations control the flush of data to disk.
# There are a few important trade-offs here:
# 1. Durability: Unflushed data may be lost if you are not using replication.
# 2. Latency: Very large flush intervals may lead to latency spikes when the flush does occur as there will be a lot of data to flush.
# 3. Throughput: The flush is generally the most expensive operation, and a small flush interval may lead to excessive seeks.
# The settings below allow one to configure the flush policy to flush data after a period of time or
# every N messages (or both). This can be done globally and overridden on a per-topic basis.
# The number of messages to accept before forcing a flush of data to disk
#log.flush.interval.messages=10000
# The maximum amount of time a message can sit in a log before we force a flush
#log.flush.interval.ms=1000
############################# Log Retention Policy #############################
# The following configurations control the disposal of log segments. The policy can
# be set to delete segments after a period of time, or after a given size has accumulated.
# A segment will be deleted whenever *either* of these criteria are met. Deletion always happens
# from the end of the log.
# The minimum age of a log file to be eligible for deletion due to age
log.retention.hours=168
# A size-based retention policy for logs. Segments are pruned from the log unless the remaining
# segments drop below log.retention.bytes. Functions independently of log.retention.hours.
#log.retention.bytes=1073741824
# The maximum size of a log segment file. When this size is reached a new log segment will be created.
log.segment.bytes=1073741824
# The interval at which log segments are checked to see if they can be deleted according
# to the retention policies
log.retention.check.interval.ms=300000
############################# Zookeeper #############################
# Zookeeper connection string (see zookeeper docs for details).
# This is a comma separated host:port pairs, each corresponding to a zk
# server. e.g. "127.0.0.1:3000,127.0.0.1:3001,127.0.0.1:3002".
# You can also append an optional chroot string to the urls to specify the
# root directory for all kafka znodes.
zookeeper.connect=localhost:2181
# Timeout in ms for connecting to zookeeper
zookeeper.connection.timeout.ms=6000
############################# Group Coordinator Settings #############################
# The following configuration specifies the time, in milliseconds, that the GroupCoordinator will delay the initial consumer rebalance.
# The rebalance will be further delayed by the value of group.initial.rebalance.delay.ms as new members join the group, up to a maximum of max.poll.interval.ms.
# The default value for this is 3 seconds.
# We override this to 0 here as it makes for a better out-of-the-box experience for development and testing.
# However, in production environments the default value of 3 seconds is more suitable as this will help to avoid unnecessary, and potentially expensive, rebalances during application startup.
group.initial.rebalance.delay.ms=0
2.2.3 kafka启动
首先进入道到afka的安装目录下的bin目录下运行一下命令
//kafka 的启动命令
./kafka-server-start.sh /usr/kafka/config/server.properties &
//命令解释说明
第二个参数表示/usr/kafka/config/server.properties kafka 运行所加载的配置文件
& linux 命令，表示后台运行出现以下一下画面，并且没有报错信息，则kfaka实例启动成功！
2.3 kaka的命令操作
2.3.1 查看当前服务器中所有的topic
/usr/kafka/bin/kafka-topics.sh --list --zookeeper localhost:21812.3.2 创建topic
/usr/kafka/bin/kafka-topics.sh --create --zookeeper localhost:2181 --replication-factor 1 --partitions 1 --topic first
//命令说明
eplication-factor 定义副本数 不能大于集群个数，超过会报错，当前为单机版本，故值为1
topic topic的名称
partitions 分区数 操作结果如下所示：
2.3.3 删除topic
/usr/kafka/bin/kafka-topics.sh --delete --zookeeper localhost:2181 --topic first操作结果如下：
2.3.4 发送消息
使用控制台自带的生产者，命令如下
/usr/kafka/bin/kafka-console-producer.sh --broker-list localhost:9092 --topic second发送以下命令
2.3.5 消费消息
同生产者一样，我们使用，命令行自带的消费者，命令如下
/usr/kafka/bin/kafka-console-consumer.sh --bootstrap-server localhost:9092 --from-beginning --topic second生产效果如下：
2.3.6 查看某个topic 的详情
/usr/kafka/bin/kafka-topics.sh --topic second --zookeeper localhost:2181 --describe效果如下
3 kafka的配置信息
由于各个版本差距变化可能较大，或发生命令或属性名改变的情况，请大家依据版本号查阅官网上对应版本号的的配置文件说明，切记！！！！
3.1 Broker的配置信息
| 属性 |
默认值 |
描述 |
| broker.id |
|
必填参数，broker的唯一标识 |
| log.dirs |
/tmp/kafka-logs |
Kafka数据存放的目录。可以指定多个目录，中间用逗号分隔，当新partition被创建的时会被存放到当前存放partition最少的目录。 |
| port |
9092 |
BrokerServer接受客户端连接的端口号 |
| zookeeper.connect |
null |
Zookeeper的连接串，格式为：hostname1:port1,hostname2:port2,hostname3:port3。可以填一个或多个，为了提高可靠性，建议都填上。注意，此配置允许我们指定一个zookeeper路径来存放此kafka集群的所有数据，为了与其他应用集群区分开，建议在此配置中指定本集群存放目录，格式为：hostname1:port1,hostname2:port2,hostname3:port3/chroot/path 。需要注意的是，消费者的参数要和此参数一致。 |
| message.max.bytes |
1000000 |
服务器可以接收到的最大的消息大小。注意此参数要和consumer的maximum.message.size大小一致，否则会因为生产者生产的消息太大导致消费者无法消费。 |
| num.io.threads |
8 |
服务器用来执行读写请求的IO线程数，此参数的数量至少要等于服务器上磁盘的数量。 |
| queued.max.requests |
500 |
I/O线程可以处理请求的队列大小，若实际请求数超过此大小，网络线程将停止接收新的请求。 |
| socket.send.buffer.bytes |
100 * 1024 |
The SO_SNDBUFF buffer the server prefers for socket connections. |
| socket.receive.buffer.bytes |
100 * 1024 |
The SO_RCVBUFF buffer the server prefers for socket connections. |
| socket.request.max.bytes |
100 * 1024 * 1024 |
服务器允许请求的最大值， 用来防止内存溢出，其值应该小于 Java heap size. |
| num.partitions |
1 |
默认partition数量，如果topic在创建时没有指定partition数量，默认使用此值，建议改为5 |
| log.segment.bytes |
1024 * 1024 * 1024 |
Segment文件的大小，超过此值将会自动新建一个segment，此值可以被topic级别的参数覆盖。 |
| log.roll.{ms,hours} |
24 * 7 hours |
新建segment文件的时间，此值可以被topic级别的参数覆盖。 |
| log.retention.{ms,minutes,hours} |
7 days |
Kafka segment log的保存周期，保存周期超过此时间日志就会被删除。此参数可以被topic级别参数覆盖。数据量大时，建议减小此值。 |
| log.retention.bytes |
-1 |
每个partition的最大容量，若数据量超过此值，partition数据将会被删除。注意这个参数控制的是每个partition而不是topic。此参数可以被log级别参数覆盖。 |
| log.retention.check.interval.ms |
5 minutes |
删除策略的检查周期 |
| auto.create.topics.enable |
true |
自动创建topic参数，建议此值设置为false，严格控制topic管理，防止生产者错写topic。 |
| default.replication.factor |
1 |
默认副本数量，建议改为2。 |
| replica.lag.time.max.ms |
10000 |
在此窗口时间内没有收到follower的fetch请求，leader会将其从ISR(in-sync replicas)中移除。 |
| replica.lag.max.messages |
4000 |
如果replica节点落后leader节点此值大小的消息数量，leader节点就会将其从ISR中移除。 |
| replica.socket.timeout.ms |
30 * 1000 |
replica向leader发送请求的超时时间。 |
| replica.socket.receive.buffer.bytes |
64 * 1024 |
The socket receive buffer for network requests to the leader for replicating data. |
| replica.fetch.max.bytes |
1024 * 1024 |
The number of byes of messages to attempt to fetch for each partition in the fetch requests the replicas send to the leader. |
| replica.fetch.wait.max.ms |
500 |
The maximum amount of time to wait time for data to arrive on the leader in the fetch requests sent by the replicas to the leader. |
| num.replica.fetchers |
1 |
Number of threads used to replicate messages from leaders. Increasing this value can increase the degree of I/O parallelism in the follower broker. |
| fetch.purgatory.purge.interval.requests |
1000 |
The purge interval (in number of requests) of the fetch request purgatory. |
| zookeeper.session.timeout.ms |
6000 |
ZooKeeper session 超时时间。如果在此时间内server没有向zookeeper发送心跳，zookeeper就会认为此节点已挂掉。 此值太低导致节点容易被标记死亡；若太高，.会导致太迟发现节点死亡。 |
| zookeeper.connection.timeout.ms |
6000 |
客户端连接zookeeper的超时时间。 |
| zookeeper.sync.time.ms |
2000 |
H ZK follower落后 ZK leader的时间。 |
| controlled.shutdown.enable |
true |
允许broker shutdown。如果启用，broker在关闭自己之前会把它上面的所有leaders转移到其它brokers上，建议启用，增加集群稳定性。 |
| auto.leader.rebalance.enable |
true |
If this is enabled the controller will automatically try to balance leadership for partitions among the brokers by periodically returning leadership to the “preferred” replica for each partition if it is available. |
| leader.imbalance.per.broker.percentage |
10 |
The percentage of leader imbalance allowed per broker. The controller will rebalance leadership if this ratio goes above the configured value per broker. |
| leader.imbalance.check.interval.seconds |
300 |
The frequency with which to check for leader imbalance. |
| offset.metadata.max.bytes |
4096 |
The maximum amount of metadata to allow clients to save with their offsets. |
| connections.max.idle.ms |
600000 |
Idle connections timeout: the server socket processor threads close the connections that idle more than this. |
| num.recovery.threads.per.data.dir |
1 |
The number of threads per data directory to be used for log recovery at startup and flushing at shutdown. |
| unclean.leader.election.enable |
true |
Indicates whether to enable replicas not in the ISR set to be elected as leader as a last resort, even though doing so may result in data loss. |
| delete.topic.enable |
false |
启用deletetopic参数，建议设置为true。 |
| offsets.topic.num.partitions |
50 |
The number of partitions for the offset commit topic. Since changing this after deployment is currently unsupported, we recommend using a higher setting for production (e.g., 100-200). |
| offsets.topic.retention.minutes |
1440 |
Offsets that are older than this age will be marked for deletion. The actual purge will occur when the log cleaner compacts the offsets topic. |
| offsets.retention.check.interval.ms |
600000 |
The frequency at which the offset manager checks for stale offsets. |
| offsets.topic.replication.factor |
3 |
The replication factor for the offset commit topic. A higher setting (e.g., three or four) is recommended in order to ensure higher availability. If the offsets topic is created when fewer brokers than the replication factor then the offsets topic will be created with fewer replicas. |
| offsets.topic.segment.bytes |
104857600 |
Segment size for the offsets topic. Since it uses a compacted topic, this should be kept relatively low in order to facilitate faster log compaction and loads. |
| offsets.load.buffer.size |
5242880 |
An offset load occurs when a broker becomes the offset manager for a set of consumer groups (i.e., when it becomes a leader for an offsets topic partition). This setting corresponds to the batch size (in bytes) to use when reading from the offsets segments when loading offsets into the offset manager’s cache. |
| offsets.commit.required.acks |
-1 |
The number of acknowledgements that are required before the offset commit can be accepted. This is similar to the producer’s acknowledgement setting. In general, the default should not be overridden. |
| offsets.commit.timeout.ms |
5000 |
The offset commit will be delayed until this timeout or the required number of replicas have received the offset commit. This is similar to the producer request timeout. |
3.2 Producer配置信息
| 属性 |
默认值 |
描述 |
| metadata.broker.list |
|
启动时producer查询brokers的列表，可以是集群中所有brokers的一个子集。注意，这个参数只是用来获取topic的元信息用，producer会从元信息中挑选合适的broker并与之建立socket连接。格式是：host1:port1,host2:port2。 |
| request.required.acks |
0 |
参见3.2节介绍 |
| request.timeout.ms |
10000 |
Broker等待ack的超时时间，若等待时间超过此值，会返回客户端错误信息。 |
| producer.type |
sync |
同步异步模式。async表示异步，sync表示同步。如果设置成异步模式，可以允许生产者以batch的形式push数据，这样会极大的提高broker性能，推荐设置为异步。 |
| serializer.class |
kafka.serializer.DefaultEncoder |
序列号类，.默认序列化成 byte[] 。 |
| key.serializer.class |
|
Key的序列化类，默认同上。 |
| partitioner.class |
kafka.producer.DefaultPartitioner |
Partition类，默认对key进行hash。 |
| compression.codec |
none |
指定producer消息的压缩格式，可选参数为： “none”, “gzip” and “snappy”。关于压缩参见4.1节 |
| compressed.topics |
null |
启用压缩的topic名称。若上面参数选择了一个压缩格式，那么压缩仅对本参数指定的topic有效，若本参数为空，则对所有topic有效。 |
| message.send.max.retries |
3 |
Producer发送失败时重试次数。若网络出现问题，可能会导致不断重试。 |
| retry.backoff.ms |
100 |
Before each retry, the producer refreshes the metadata of relevant topics to see if a new leader has been elected. Since leader election takes a bit of time, this property specifies the amount of time that the producer waits before refreshing the metadata. |
| topic.metadata.refresh.interval.ms |
600 * 1000 |
The producer generally refreshes the topic metadata from brokers when there is a failure (partition missing, leader not available…). It will also poll regularly (default: every 10min so 600000ms). If you set this to a negative value, metadata will only get refreshed on failure. If you set this to zero, the metadata will get refreshed after each message sent (not recommended). Important note: the refresh happen only AFTER the message is sent, so if the producer never sends a message the metadata is never refreshed |
| queue.buffering.max.ms |
5000 |
启用异步模式时，producer缓存消息的时间。比如我们设置成1000时，它会缓存1秒的数据再一次发送出去，这样可以极大的增加broker吞吐量，但也会造成时效性的降低。 |
| queue.buffering.max.messages |
10000 |
采用异步模式时producer buffer 队列里最大缓存的消息数量，如果超过这个数值，producer就会阻塞或者丢掉消息。 |
| queue.enqueue.timeout.ms |
-1 |
当达到上面参数值时producer阻塞等待的时间。如果值设置为0，buffer队列满时producer不会阻塞，消息直接被丢掉。若值设置为-1，producer会被阻塞，不会丢消息。 |
| batch.num.messages |
200 |
采用异步模式时，一个batch缓存的消息数量。达到这个数量值时producer才会发送消息。 |
| send.buffer.bytes |
100 * 1024 |
Socket write buffer size |
| client.id |
“” |
The client id is a user-specified string sent in each request to help trace calls. It should logically identify the application making the request. |
3.3 Consumer配置文件
| 属性 |
默认值 |
描述 |
| group.id |
|
Consumer的组ID，相同goup.id的consumer属于同一个组。 |
| zookeeper.connect |
|
Consumer的zookeeper连接串，要和broker的配置一致。 |
| consumer.id |
null |
如果不设置会自动生成。 |
| socket.timeout.ms |
30 * 1000 |
网络请求的socket超时时间。实际超时时间由max.fetch.wait + socket.timeout.ms 确定。 |
| socket.receive.buffer.bytes |
64 * 1024 |
The socket receive buffer for network requests. |
| fetch.message.max.bytes |
1024 * 1024 |
查询topic-partition时允许的最大消息大小。consumer会为每个partition缓存此大小的消息到内存，因此，这个参数可以控制consumer的内存使用量。这个值应该至少比server允许的最大消息大小大，以免producer发送的消息大于consumer允许的消息。 |
| num.consumer.fetchers |
1 |
The number fetcher threads used to fetch data. |
| auto.commit.enable |
true |
如果此值设置为true，consumer会周期性的把当前消费的offset值保存到zookeeper。当consumer失败重启之后将会使用此值作为新开始消费的值。 |
| auto.commit.interval.ms |
60 * 1000 |
Consumer提交offset值到zookeeper的周期。 |
| queued.max.message.chunks |
2 |
用来被consumer消费的message chunks 数量， 每个chunk可以缓存fetch.message.max.bytes大小的数据量。 |
| auto.commit.interval.ms |
60 * 1000 |
Consumer提交offset值到zookeeper的周期。 |
| queued.max.message.chunks |
2 |
用来被consumer消费的message chunks 数量， 每个chunk可以缓存fetch.message.max.bytes大小的数据量。 |
| fetch.min.bytes |
1 |
The minimum amount of data the server should return for a fetch request. If insufficient data is available the request will wait for that much data to accumulate before answering the request. |
| fetch.wait.max.ms |
100 |
The maximum amount of time the server will block before answering the fetch request if there isn’t sufficient data to immediately satisfy fetch.min.bytes. |
| rebalance.backoff.ms |
2000 |
Backoff time between retries during rebalance. |
| refresh.leader.backoff.ms |
200 |
Backoff time to wait before trying to determine the leader of a partition that has just lost its leader. |
| auto.offset.reset |
largest |
What to do when there is no initial offset in ZooKeeper or if an offset is out of range ;smallest : automatically reset the offset to the smallest offset; largest : automatically reset the offset to the largest offset;anything else: throw exception to the consumer |
| consumer.timeout.ms |
-1 |
若在指定时间内没有消息消费，consumer将会抛出异常。 |
| exclude.internal.topics |
true |
Whether messages from internal topics (such as offsets) should be exposed to the consumer. |
| zookeeper.session.timeout.ms |
6000 |
ZooKeeper session timeout. If the consumer fails to heartbeat to ZooKeeper for this period of time it is considered dead and a rebalance will occur. |
| zookeeper.connection.timeout.ms |
6000 |
The max time that the client waits while establishing a connection to zookeeper. |
| zookeeper.sync.time.ms |
2000 |
How far a ZK follower can be behind a ZK leader |
至此，kafka安装基本到一段落，之后可能会更新，博文分析kafa的工作流程和使用javaAPI操作kafka,欢迎大家关注