How to Install, configure and use Clush
Clush is an open source tool that allows you to execute commands in parallel across the nodes in the cluster. This blog describes how to install clush, configure and use clush to run commands on multiple nodes in parallel.
This blog assumes you have ssh trust created from node 1 (10.10.70.106) to rest of nodes (node2-node4) .
The clush utility need to be only installed on one node, usually the primary node (10.10.70.106) in the cluster where we will run commands in parallel and gather stats .
Installation :
Installation of clush utility is simple and straightforward, i.e enable EPEL repo ( as per your OS version) and yum install the package as listed in 3 steps below.
1) wget http://download.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm
2) rpm -Uvh epel-release-6*.rpm
3) yum install clustershell -y
Configuration :
I have a 4 node mapr cluster as listed below.
[root@node1 ~]# maprcli node list -columns configuredservice
node1 tasktracker,webserver,cldb,fileserver,hoststats 10.10.70.106
node2 tasktracker,cldb,fileserver,hoststats 10.10.70.107
node3 fileserver,tasktracker,hoststats,jobtracker 10.10.70.108
node4 fileserver,tasktracker,hoststats,jobtracker 10.10.70.109
[root@node1 ~]#
Now edit "/etc/clustershell/groups" file to group the nodes which has same services installed.
all: node[1-4]
zk: 10.10.70.106 10.10.70.107 10.10.70.108
jt: 10.10.70.108,10.10.70.109
web: 10.10.70.106
cldb: 10.10.70.106,10.10.70.107
[root@node1 ~]#
Execution/Utilization :
1) To run the command in parallel on all 4 nodes
[root@node1 ~]# clush -a date
node4: Mon Jul 6 14:26:37 PDT 2015
node3: Mon Jul 6 14:26:37 PDT 2015
node2: Mon Jul 6 14:26:37 PDT 2015
[root@node1 ~]#
2) To get cleaner way output where same output for nodes is grouped.
---------------
node[1-4] (4)
---------------
Mon Jul 6 14:28:41 PDT 2015
[root@node1 ~]#
3) To get into interactive cluster shell and get ouput for all nodes you can use "clush -a"
[root@node1 ~]# clush -a
Enter 'quit' to leave this interactive mode
Working with nodes: node[1-4]
clush> date
node1: Mon Jul 6 14:29:42 PDT 2015
node3: Mon Jul 6 14:29:42 PDT 2015
node2: Mon Jul 6 14:29:42 PDT 2015
node4: Mon Jul 6 14:29:42 PDT 2015
clush> uname -a
node2: Linux node2.mycluster.com 2.6.32-431.el6.x86_64 #1 SMP Fri Nov 22 03:15:09 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
node4: Linux node4.mycluster.com 2.6.32-431.el6.x86_64 #1 SMP Fri Nov 22 03:15:09 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
node1: Linux node1.mycluster.com 2.6.32-431.el6.x86_64 #1 SMP Fri Nov 22 03:15:09 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
node3: Linux node3.mycluster.com 2.6.32-431.el6.x86_64 #1 SMP Fri Nov 22 03:15:09 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
clush>
4) To copy file /root/abi to all cluster nodes .
[root@node1 ~]# clush -a -c /root/abi
[root@node1 ~]#
Verify :
node1: /root/abi
node4: /root/abi
node3: /root/abi
node2: /root/abi
[root@node1 ~]#
5) To remove file /root/abi to all cluster nodes
[root@node1 ~]# clush -a rm -rf /root/abi
[root@node1 ~]#
Verify :
[root@node1 ~]#clush -a ls /root/abi
node1: ls: cannot access /root/abi: No such file or directory
clush: node1: exited with exit code 2
node3: ls: cannot access /root/abi: No such file or directory
clush: node3: exited with exit code 2
node2: ls: cannot access /root/abi: No such file or directory
clush: node2: exited with exit code 2
node4: ls: cannot access /root/abi: No such file or directory
clush: node4: exited with exit code 2
[root@node1 ~]#
6) To copy the file to different destination on nodes via clush and then verify.
[root@node1 ~]# clush -a ls /tmp/abi
node2: /tmp/abi
node1: /tmp/abi
node4: /tmp/abi
node3: /tmp/abi
[root@node1 ~]#
7) To run specific command on group of nodes described in "/etc/clustershell/groups" file.
[root@node1 ~]# clush -g zk date
10.10.70.106: Mon Jul 6 14:40:24 PDT 2015
10.10.70.108: Mon Jul 6 14:40:24 PDT 2015
10.10.70.107: Mon Jul 6 14:40:24 PDT 2015
[root@node1 ~]# clush -g jt date
10.10.70.108: Mon Jul 6 14:40:33 PDT 2015
10.10.70.109: Mon Jul 6 14:40:33 PDT 2015
[root@node1 ~]#
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