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/********************** kafka **********************/ 

Kafka  cluster colony
Point to point mode , Thread monitoring is required
Release / subscribe , The push speed is inconsistent with the client speed

Save the message according to topic categorize .
sender producer
The recipient consumer
Multiple instances , Each instance (server) be called broker

kafka rely on zookeeper Cluster save meta Information , Ensure system availability . Client requests can only Leader Handle
partition: Partition

Kafka Cluster colony ：
Broker1 :
TopcicA(partition0) Leader
TopcicA(partition1) Follower
Broker2 :
TopcicA(partition0) Follower
TopcicA(partition1) Leader
Broker3 :
Partition0(message0、message1) topic It's divided into one area

Follower Do nothing

Consumer groups cannot consume the same partition at the same time

ConsumerA

Consumer group

ConsumerB

One consumer can consume more than one topic

mkdir logs
cd config
Set up the cluster , modify ： server.properties

broker.id=0
delete.topic.enable=true
log.dirs=/opt/module
zookeeper.connect=hadoop102:2181,hadoop103:2181,hadoop104:2181

cd ..
xsync kafka/

vi server.properties
broker.id=1
broker.id=2

start-up kafka Start before Zookeeper:
zkstart.sh
Check whether the startup is successful :
/opt/module/zookeeper-3.4.10/bin/zkServer.sh status

Mode:follower Indicating successful startup .

start-up kafka: 
machine 1：bin/kafka-server-start.sh config/server/properties
machine 2：bin/kafka-server-start.sh config/server/properties
machine 3：bin/kafka-server-start.sh config/server/properties

Each machine needs to be started separately
util.sh Check the startup process of three machines

establish                                                                                       Partition number 2 individual               replications 2 individual         topic name
bin/kafka-topics.sh --create --zookeeper hadoop102:2181 --partitions 2 -- replication-factor 2  --topic first
see
bin/kafka-topics.sh --list --zookeeper hadoop102:2181
Check the log
cd logs 

Three machines , Number of copies set 5, Will report a mistake , Prompt for up to copies 3.
establish                                                                                           Partition 2            copy 5                        topic name
bin/kafka-topics.sh --create --zookeeper hadoop102:2181 --partitions 2 -- replication-factor 5 --topic second

Start producer ：                                                                            To which topic send out
bin/kafka-console-producer.sh --broker -list hadoop102:9092 --topic first
>hello 
>yz

Start consumer （ colony ） stay 103 Machine start up
                                                                    Which one to consume topic, Get the latest data       Consume from the beginning   
bin/kafka-console-consumer.sh --zookeeper hadoop102:2181 --topic first      --from-beginning

Use bootstrap-server Instead of zookeeper To eliminate the warning
                                                                                Which one to consume topic, Get the latest data     Consume from the beginning   
bin/kafka-console-consumer.sh --bootstrap-server hadoop102:2181 --topic first        --from-beginning

Data exists topic, Using machines 104 See how many topic
bin/kafka-topics.sh --list --zookeeper hadoop102:2181
__consumer_offsets explain ： The system automatically creates , This should be used bootstrap after , Save to local topic
first

see topic details                                                           Description specifies topic
bin/kafka-topics.sh --zookeeper hadoop102:2181 --describeopic first
                          Partition              Leader machine     copy                 For election  
Topic:first        Partition: 0     Leader: 0        Replicas: 0,2    Isr: 0,2
Topic:first        Partition: 1     Leader: 1        Replicas: 1,0    Isr: 1,0
Isr: 0,2（ These two copies and leader Closest , Forward row ,leader After hanging up , Take the next one instead Leader）

machine whether Leader,Leader Only responsible for the producer to write data ,Follower Initiative from Leader Pull data .
0    Leader
1    Follower
2    Follower

Delete topic, You will be prompted to set to true
bin/kafka-topics.sh --delete --zookeeper hadoop102:2181 -topic first

Create from New topic
                                                                                            Partition 1 individual         copy 3 individual                    Appoint topic name
bin/kafka-topics.sh --create --zookeeper hadoop102:2181 --partitions 1 --replication-factro 3 --topic first