Shulou(Shulou.com)06/03 Report--

1. Brief introduction of Environmental preparation

ZooKeeper is a distributed, open source distributed application coordination service, an open source implementation of Google's Chubby, and an important component of Hadoop and Hbase. It is a software that provides consistency services for distributed applications, including configuration maintenance, domain name services, distributed synchronization, group services and so on.

The goal of ZooKeeper is to encapsulate complex and error-prone key services and provide users with simple and easy-to-use interfaces and systems with efficient performance and stable functions.

ZooKeeper contains a simple set of primitives that provides an interface between Java and C.

The ZooKeeper code version provides interfaces for distributed exclusive locks, elections, and queues at $zookeeper_home\ src\ recipes. There are two versions of distribution lock and queue, Java and C, and only Java version is elected.

Principle

ZooKeeper is based on Fast Paxos algorithm, Paxos algorithm has the problem of live lock, that is, when there are multiple proposer staggered submissions, it is possible that no proposer can be submitted successfully due to mutual exclusion, while Fast Paxos has made some optimizations to produce a leader (leader) through election, and only leader can submit proposer. The specific algorithm can be seen in Fast Paxos. Therefore, if you want to understand ZooKeeper, you must first know something about Fast Paxos.

The basic operation flow of ZooKeeper:

1. Elect Leader.

2. Synchronize data.

3. There are many algorithms in the process of electing Leader, but the election criteria are the same.

4. Leader should have the highest execution ID, similar to root permission.

5. Most of the machines in the cluster respond and accept the selected Leader.

1.1 download zooKeeper

    looks up the hadoop2.7.3 documentation and we can see that hadoop2.7.3 uses the zookeeper-3.4.2 version when building high availability, so we also follow the instructions on the hadoop website, and then we install the zookeeper-3.4.2 version. Go to the official website to download the ZooKeeper3.4.2 version

    official website address: https://zookeeper.apache.org/

Click Download

1.3 install zooKeeper#1. Unzip the zookeeper installation package to the / opt/bigdata/ directory [root@node1] # tar-xzvf zookeeper-3.4.2.tar.gz-C / opt/bigdata/ # enter the command and enter # 2. Change to [root@node1 ~] # cd / opt/bigdata/#3 under the bigdata directory. According to the way of installing hadoop, change the group of zookeeper installation directory to hadoop:hadoop# and modify the user and group of zookeeper installation directory to hadoop:hadoop [root@node1 bigdata] # chown-R hadoop:hadoop zookeeper-3.4.2/#4. Modify the read and write permissions of the zookeeper installation directory [root@node1 bigdata] # chmod-R 755 zookeeper-3.4.2/1.4 configure zooKeeper environment variable # 1. Switch to [root@node1 bigdata] # su-hadoopLast login: Thu Jul 18 16:07:39 CST 2019 on pts/0 [hadoop@node1 ~] $cd / opt/bigdata/zookeeper-3.4.2/ [hadoop@node1 zookeeper-3.4.2] $cd. [hadoop@node1 bigdata] $cd ~ # 2 under the hadoop user directory. Modify the environment variable configuration file [hadoop@node1 ~] $vi. Bash _ profile# Get the aliases and functions# Get the aliases and functionsif [- f ~ /. Bashrc] under the hadoop user; then. ~ / .bashrcfi # User specific environment and startup programsJAVA_HOME=/usr/java/jdk1.8.0_211-amd64HADOOP_HOME=/opt/bigdata/hadoop-2.7.3SPARK_HOME=/opt/spark-2.4.3-bin-hadoop2.7M2_HOME=/opt/apache-maven-3.0.5#3. Add the environment variable ZOOKEEPER_HOMEZOOKEEPER_HOME=/opt/bigdata/zookeeper-3.4.2/PATH=$PATH:$HOME/bin:$JAVA_HOME/bin:$HADOOP_HOME/bin:$HADOOP_HOME/sbin:$M2_HOME/bin#4. Zookeeper. Add the environment variable ZOOKEEPER_HOME of zookeeper to path PATH=$PATH:$SPARK_HOME/bin:$SPARK_HOME/sbin:$ZOOKEEPER_HOME/binexport JAVA_HOMEexport HADOOP_HOMEexport M2_HOMEexport SPARK_HOMEexport HADOOP_CONF_DIR=$HADOOP_HOME/etc/hadoopexport HDFS_CONF_DIR=$HADOOP_HOME/etc/hadoop#5. Export the zookeeper environment variable export ZOOKEEPER_HOME#6. Save the changes: wq! # remember to enter # 7. Make the environment variable take effect [hadoop@node1 ~] $source. Bash _ profile#8. Enter zk and press the Tab key [hadoop@node1 ~] $zk# on the left side of the keyboard to have the following prompt. The table name zookeeper completes the configuration, zkCleanup.sh zkCli.cmd zkCli.sh zkEnv.cmd zkEnv.sh zkServer.cmd zkServer.sh [hadoop@node1 ~] $zk1.5 modifies the zookeeper cluster configuration file

    changes the directory to the conf directory under the installation directory of zookeeper to copy the zoo_sample.cfg file to zoo.cfg

[hadoop@node1] $cd / opt/bigdata/zookeeper-3.4.2/conf/ [hadoop@node1 conf] $lltotal 12-rwxr-xr-x 1 hadoop hadoop 535 Dec 22 2011 configuration.xsl-rwxr-xr-x 1 hadoop hadoop 2161 Dec 22 2011 log4j.properties-rwxr-xr-x 1 hadoop hadoop 808 Dec 22 2011 zoo_sample.cfg#1. Copy the zoo_sample.cfg template configuration file into the formal configuration file zoo.cfg [hadoop@node1 conf] $cp zoo_sample.cfg zoo.cfg [hadoop@node1 conf] $lltotal 16-rwxr-xr-x 1 hadoop hadoop 535 Dec 22 2011 configuration.xsl-rwxr-xr-x 1 hadoop hadoop 2161 Dec 22 2011 log4j.properties-rwxr-xr-x 1 hadoop hadoop 808 Jul 19 11:20 zoo.cfg-rwxr-xr-x 1 hadoop hadoop 808 Dec 22 2011 zoo_ sample.cfg [Hadoop @ node1 conf] $

    modifies the value of dataDir to dataDir=/var/lib/zookeeper, and adds the following configuration at the end of the file:

Server.1=node1:2888:3888 server.2=node2:2888:3888 server.3=node3:2888:3888

Remember to save the configuration file after you modify it

# The number of milliseconds of each ticktickTime=2000# The number of ticks that the initial# synchronization phase can takeinitLimit=10# The number of ticks that can pass between# sending a request and getting an acknowledgementsyncLimit=5# the directory where the snapshot is stored.# do not use / tmp for storage, / tmp here is just# example sakes.dataDir=/var/lib/zookeeper# the port at which the clients will connectclientPort=2181# the maximum number of client connections.# increase this if you need to handle more clients#maxClientCnxns=60## Be sure to read the maintenance section of the# administrator guide before turning on autopurge. Let's start the course. Kaikeba.com selected domain masters will only create myid files for talent empowerment 61.6. create myid files in the / var/lib/zookeeper directory corresponding to node node1,node2,node3 (directory configured by dataDir / var/lib/zookeeper). The contents of several files are in the following order. As shown in the following figure, we switch to root users and create zookeeper directories under / var/lib directory, because hadoop users do not have write permission to the / var/lib directory. So when we create a zookeeper directory, we need to switch to the root user (with maximum permissions) # # http://zookeeper.apache.org/doc/current/zookeeperAdmin.html#sc_maintenance## The number of snapshots to retain in dataDir#autopurge.snapRetainCount=3# Purge task interval in hours# Set to "0" to disable autopurge feature#autopurge.purgeInterval=1server.1=node1:2888:3888server.2=node2:2888:3888server.3=node3:2888:3888# after modifying the configuration file remember to save 1.6 to create the myid file

Create a myid file under the / var/lib/zookeeper directory corresponding to the node node1,node2,node3 (record / var/lib/zookeeper configured by dataDir), and the contents of several files are in turn: 1Jing 2jue 3. Switch to the root user and create the zookeeper directory under the / var/lib directory. Since the hadoop user does not have write permission to the / var/lib directory, we need to change to the

Root user (with maximum permissions) [hadoop@node1 conf] $vi zoo.cfg#1. Switch to root user [hadoop@node1 conf] $su-rootPassword:Last login: Fri Jul 19 10:53:59 CST 2019 from 192.168.200.1 on pts/0#2. Create the zookeeper directory [root@node1 ~] # mkdir-p / var/lib/zookeeper#3. Go to the / var/lib/zookeeper/ directory [root@node1 ~] # cd / var/lib/zookeeper/You have new mail in / var/spool/mail/root#4. Create the myid configuration file [root@node1 zookeeper] # touch myid#5. Edit the myid file and enter 1. We are currently editing the myid file of the node of node1. The myid content of node2 is 2 and the myid content of 3 [root@node1 zookeeper] # vi myidYou have new mail in / var/spool/mail/root#6. Check that the content of the myid file is 1 [root@node1 zookeeper] # cat myid1You have new mail in / var/spool/mail/root1.7 to modify myid directory permissions # 1. Remember to modify the group and read and write permissions of the zookeeper directory [root@node1 zookeeper] # cd.. You have new mail in / var/spool/mail/root#2 after configuration. Modify the group [root@node1 lib] # chown-R hadoop:hadoop zookeeper/#3 to which the zookeeper directory belongs. Modify the read and write permissions of the zookeeper directory to 755 [root@node1 lib] # chmod-R 755 zookeeper/ [root@node1 lib] # 2, copy zookeeper#1. Copy the zookeeper directory under the / var/lib directory to the / var/lib directory of node2 and node3 to [root@node1 lib] # scp-r zookeeper node2:$PWD [root@node1 lib] # scp-r zookeeper node3:$PWD#2. Copy the zookeeper installation directory to the / opt/bigdata directory under node2 and node3 installation directory [root@node1 lib] # scp-r / opt/bigdata/zookeeper-3.4.2/ node2:/opt/bigdata/ [root@node1 lib] # scp-r / opt/bigdata/zookeeper-3.4.2/ node3:/opt/bigdata/3, modify the relevant directory permissions of node2 and node3 node zookeeper

Modify node2 node zookeeper related directory permissions

# 1. Modify the group and read and write permissions of zookeeper's myid configuration directory [root@node2 lib] # cd ~ [root@node2 ~] # chown-R hadoop:hadoop / var/lib/zookeeper [root@node2 ~] # chmod-R 755 / var/lib/zookeeper#2. Modify the group and read and write permissions of the zookeeper installation directory [root@node2 ~] # chown-R hadoop:hadoop / opt/bigdata/zookeeper-3.4.2/You have new mail in / var/spool/mail/root [root@node2 ~] # chmod-R 755 / opt/bigdata/zookeeper-3.4.2/ [root@node2 ~] #

Modify node3 node zookeeper related directory permissions

# 1. Modify the group and read and write permissions of zookeeper's myid configuration directory [root@node3 bigdata] # cd ~ You have new mail in / var/spool/mail/root [root@node3 ~] # chown-R hadoop:hadoop / var/lib/zookeeper [root@node3 ~] # chmod-R 755 / var/lib/zookeeper#2. Modify the group and read and write permissions of the zookeeper installation directory [root@node3 ~] # chown-R hadoop:hadoop / opt/bigdata/zookeeper-3.4.2/You have new mail in / var/spool/mail/root [root@node3 ~] # chmod-R 755 / opt/bigdata/zookeeper-3.4.2/ [root@node3 ~] # 4, modify the myid file contents of node2 and node3

Modify the myid content of the node2 node zookeeper to 2:

[root@node2 ~] # vi / var/lib/zookeeper/myidYou have new mail in / var/spool/mail/root [root@node2 ~] # cat / var/lib/zookeeper/myid2 [root@node2 ~] #

Modify the myid content of node3 node zookeeper to 3

[root@node3 ~] # vi / var/lib/zookeeper/myidYou have new mail in / var/spool/mail/root [root@node3 ~] # cat / var/lib/zookeeper/myid3 [root@node3 ~] # 5, configure zookeeper environment variables for node2 and node3

We remotely copy the hadoop user's environment variable configuration file on the node1 node to the hadoop user home directory of node2 and node3.

# 1. If the currently logged in user is a root user, you need to switch to the hadoop user. If the current user is a hadoop user, Please change the directory to the hadoop user's home directory Remote copy of environment variable files is in progress. [root@node1 lib] # su-hadoopLast login: Fri Jul 19 11:08:44 CST 2019 on pts/0 [hadoop@node1 ~] $scp .bash _ profile node2:$PWD.bash_profile 100% 68164.8KB/s 00:00 [hadoop@node1 ~] $scp .ba sh_profile node3:$PWD.bash_profile 100% 681156.8KB/s 00:00 [hadoop@node1 ~] $5.1 make the environment variables for node2 and node3 effective

Make the environment variable of node2's hadoop take effect

# Note: switch to hadoop user # 1. Make the environment variable take effect [hadoop@node2 ~] $source. Bash _ profile#2. Type zk and press the Tab key [hadoop@node2 ~] $zk#3 on the left side of the keyboard. The following command and shell script prompt indicates that the environment variable of zookeeper was configured successfully. ZkCleanup.sh zkCli.sh zkEnv.sh zkServer.shzkCli.cmd zkEnv.cmd zkServer.cmd [hadoop@node2 ~] $zk

Make the environment variable of node3's hadoop take effect

# Note: switch to hadoop user under [root@node3 bigdata] # su-hadoopLast login: Thu Jul 18 15:37:50 CST 2019 on: 0room1. Make the environment variable take effect [hadoop@node3 ~] $source. Bash _ profile#2. Type zk and press the Tab key [hadoop@node3 ~] $zk#3 on the left side of the keyboard. The following command and shell script prompt indicates that the environment variable of zookeeper was configured successfully. ZkCleanup.sh zkCli.sh zkEnv.sh zkServer.shzkCli.cmd zkEnv.cmd zkServer.cmd [hadoop@node3 ~] $zk6. Start zookeeper Cluster 6.1 start zookeeper Cluster

Starting zookeeper cluster needs to be started manually on three machines in turn. Before starting, users need to be switched to hadoop users on all three machines.

Start zookeeper on node1

[hadoop@node1 ~] $zkServer.sh startJMX enabled by defaultUsing config: / opt/bigdata/zookeeper-3.4.2/bin/../conf/zoo.cfgStarting zookeeper. STARTED [hadoop@node1 ~] $

Start zookeeper on node2

[hadoop@node2 ~] $zkServer.sh startJMX enabled by defaultUsing config: / opt/bigdata/zookeeper-3.4.2/bin/../conf/zoo.cfgStarting zookeeper. STARTED [hadoop@node2 ~] $

Start zookeeper on node3

[hadoop@node3 ~] $zkServer.sh startJMX enabled by defaultUsing config: / opt/bigdata/zookeeper-3.4.2/bin/../conf/zoo.cfgStarting zookeeper. STARTED [hadoop@node3 ~] $6.2View zookeeper cluster status

Use the zkServer.sh status command to view the status on each of the three nodes

View on node1

[hadoop@node1 bin] $zkServer.sh statusJMX enabled by defaultUsing config: / opt/bigdata/zookeeper-3.4.2/bin/../conf/zoo.cfgMode: follower [hadoop@node1 bin] $

View on node2

[hadoop@node2 bin] $zkServer.sh statusJMX enabled by defaultUsing config: / opt/bigdata/zookeeper-3.4.2/bin/../conf/zoo.cfgMode: follower [hadoop@node2 bin] $

View on node3

[hadoop@node3 bin] $zkServer.sh statusJMX enabled by defaultUsing config: / opt/bigdata/zookeeper-3.4.2/bin/../conf/zoo.cfgMode: leader [hadoop@node3 bin] $

At this point, our zookeeper cluster installation is complete.

6.3 problems encountered in zooKeeper installation

Since the zookeeper-3.4.2 version is used in the official documentation according to the hadoop2.7.3 version, but the zookeeper-3.4.2 version is relatively low, after starting zookeeper, we can use the jps command or the ps-ef | grep zookeeper command to check the status of the zookeeper main process, but we find it is normal. If we use the zkServer.sh status command to check the status of zookeeper, it shows that it is abnormal, no matter how many times we start it, we will get the same result.

[hadoop@node1 bin] $zkServer.sh statusJMX enabled by defaultUsing config: / opt/bigdata/zookeeper-3.4.2/bin/../conf/zoo.cfgError contacting service. It is probably not running. [hadoop@node2 bin] $zkServer.sh statusJMX enabled by defaultUsing config: / opt/bigdata/zookeeper-3.4.2/bin/../conf/zoo.cfgError contacting service. It is probably not running. [hadoop@node3 bin] $zkServer.sh statusJMX enabled by defaultUsing config: / opt/bigdata/zookeeper-3.4.2/bin/../conf/zoo.cfgError contacting service. It is probably not running.

The analysis is mainly caused by the following two reasons:

The nc tool is not installed on 1.centos7.

The nc command in the 2.zookeeper startup script uses invalid parameters in different versions of linux, resulting in an exception or a state of

Caused by the null state.

Solution:

1. Install the nc tool on each of the three nodes using yum

Yum install nc-y

two。 Modify the contents of the zkServer.sh script file in the bin directory under the zookeeper installation directory

After the modification is completed, we can see the status of zookeeper after using zkServer.sh status.

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