MongoDB 3 Node replication cluster

MongoDB 3 Node replication cluster

MongoDB Fail Over Cluster

Introduction: Replication provides redundancy and increases data availability. With multiple copies of data on different database servers, replication protects a database from the loss of a single server. Replication also allows you to recover from hardware failure and service interruptions. With additional copies of the data, you can dedicate one to disaster recovery, reporting, or backup MongoDB 3 Node replication cluster
Operating System:  Red Hat Enterprise Linux Server release 6.5 (Santiago)

Scenario: I used three machines and configure the name resolution for all machine by edit the entry in /etc/hosts file like below

[root@TechTutorial ~]#cat /etc/hosts
 #####################################################################################
 127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4
 ::1 localhost localhost.localdomain localhost6 localhost6.localdomain6
 192.168.42.139 machine1.com
 192.168.42.142 machine2.com
 192.168.42.141 machine3.com
 #####################################################################################
[root@TechTutorial ~]#vim /etc/yum.repos.d/mongodb-org-3.0.repo
 ## >> Add below Lines in file <<##
 #####################################################################################
 [mongodb-org-3.0]
 name=MongoDB Repository
 baseurl=https://repo.mongodb.org/yum/redhat/$releasever/mongodb-org/3.0/x86_64/
 gpgcheck=0
 enabled=1
 #####################################################################################

 

[root@TechTutorial ~]#yum install -y mongodb-org
[root@TechTutorial ~]#cp /usr/bin/mongod /usr/bin/mongod-new
[root@TechTutorial ~]#cp /etc/mongod.conf /etc/mongod-new.conf
[root@TechTutorial ~]#cp /etc/init.d/mongod /etc/init.d/mongd-new
[root@TechTutorial ~]#mkdir /DATA
[root@TechTutorial ~]#vim /etc/mongod-new.conf

## >> Change these lines in config file  << ##
 ####################################################################################
 fork=true
 port=30003
 dbpath=/DATA/
 bind_ip= 192.168.42.139,127.0.0.1
 replSet=rs0
 ####################################################################################

 

[root@TechTutorial ~]#touch /etc/sysconfig/mongod-new
[root@TechTutorial ~]# vim /etc/init.d/mongod-new
#Delete all previous configuration of startup and use this startup script and added these bold lines accordingly#
 #!/bin/bash
 #
 # mongodb Startup script for the mongodb server
 #
 # chkconfig: - 64 36
 # description: MongoDB Database Server
 #
 # processname: mongod-new
 #
 # Source function library
 . /etc/rc.d/init.d/functions

if [ -f /etc/sysconfig/mongod-new ]; then
 . /etc/sysconfig/mongod-new
 fi

prog="mongod-new"
 mongod="/usr/bin/mongod-new"
 config_file="/etc/mongod-new.conf"
 RETVAL=0

start() {
 echo -n $"Starting $prog: "
 daemon $mongod "-f $config_file --fork --logpath /var/log/mongod-new.log --logappend 2>&1 >>/var/log/mongod-new.log"
 RETVAL=$?
 echo
 [ $RETVAL -eq 0 ] && touch /var/lock/subsys/$prog
 return $RETVAL
 }

stop() {
 echo -n $"Stopping $prog: "
 killproc $prog
 RETVAL=$?
 echo
 [ $RETVAL -eq 0 ] && rm -f /var/lock/subsys/$prog
 return $RETVAL
 }

reload() {
 echo -n $"Reloading $prog: "
 killproc $prog -HUP
 RETVAL=$?
 echo
 return $RETVAL
 }

case "$1" in
 start)
 start
 ;;
 stop)
 stop
 ;;
 restart)
 stop
 start
 ;;
 condrestart)
 if [ -f /var/lock/subsys/$prog ]; then
 stop
 start
 fi
 ;;
 reload)
 reload
 ;;
 status)
 status $mongod
 RETVAL=$?
 ;;
 *)
 echo $"Usage: $0 {start|stop|restart|condrestart|reload|status}"
 RETVAL=1
 esac

exit $RETVAL

Check permission on all files

[root@TechTutorial ~]#ll /etc/mongod-new.conf
 -rw-r--r-- 1 root root 1563 Jun 26 16:09 /etc/mongod-new.conf

[root@TechTutorial ~]#ll /etc/init.d/mongod-new
 -rwxr-xr-x 1 root root 1189 Jun 26 03:47 /etc/init.d/mongod-new

[root@TechTutorial ~]# ll /usr/bin/mongod-new
 -rwxr-xr-x 1 root root 21519920 Jun 25 21:26 /usr/bin/mongod-new
 
Now Start the service
[root@TechTutorial ~]# /etc/init.d/mongod-new start
[root@TechTutorial ~]# ps -elf | grep mongod-new
 1 S root 2507 1 1 80 0 - 799822 poll_s 13:47 ? 00:02:37 /usr/bin/mongod-new -f /etc/mongod-new.conf --fork --logpath /var/log/mongod-new.log --logappend
 0 S root 13276 2272 0 80 0 - 25811 pipe_w 16:32 pts/0 00:00:00 grep mongod-new

[root@TechTutorial ~]# netstat -tulnp | grep mongod-new
 tcp 0 0 127.0.0.1:30003 0.0.0.0:* LISTEN 18282/mongod-new
 tcp 0 0 192.168.42.139:30003 0.0.0.0:* LISTEN 18282/mongod-new

IMPORTANT:- Proceed to further Please read below text carefully
Same steps revise on machine2 and machine3 then after come to machine1 or where you want to run mongoDB as master(Primary)

Note: Before starting or login to mongo shell Set IPTABLES rule and SELinux policy otherwise stop iptables service and disabled selinux policy and remember one thing before proceed or login to mongo shell you must start service of mongod on all servers then proceed to next step.
If you want to run MongoDB in Enforcing mode
Enable access to the relevant ports (e.g. 30003) for SELinux if in enforcing mode. For settings, this can be accomplished by running this command

[root@TechTutorial ~]# semanage port -a -t mongod-new_port_t -p tcp 3003
[root@TechTutorial ~]# mongo localhost:30003
 > rs.initiate()
 {
 "info2" : "no configuration explicitly specified -- making one",
 "me" : "mongodslave2.com:30003",
 "ok" : 1
 }
 rs0:OTHER> rs.add("mongodmaster.com:30004")
 { "ok" : 1 }
 rs0:PRIMARY> rs.conf()
 2015-06-26T04:03:27.146+0530 E QUERY TypeError: Object function () { return "try rs.help()"; } has no method 'connf'
 at (shell):1:4MongoDB Fail Over Cluster
 # mongo localhost:30003
 > rs.initiate()
 {
 "info2" : "no configuration explicitly specified -- making one",
 "me" : "mongodslave2.com:30003",
 "ok" : 1
 }
 rs0:OTHER> rs.add("mongodmaster.com:30004")
 { "ok" : 1 }
 rs0:PRIMARY> rs.conf()
 2015-06-26T04:03:27.146+0530 E QUERY TypeError: Object function () { return "try rs.help()"; } has no method 'connf'
 at (shell):1:4
 rs0:PRIMARY> rs.conf()
 {
 "_id" : "rs0",
 "version" : 2,
 "members" : [
 {
 "_id" : 0,
 "host" : "mongodslave2.com:30003",
 "arbiterOnly" : false,
 "buildIndexes" : true,
 "hidden" : false,
 "priority" : 1,
 "tags" : {
},
 "slaveDelay" : 0,
 "votes" : 1
 },
 {
 "_id" : 1,
 "host" : "mongodmaster.com:30004",
 "arbiterOnly" : false,
 "buildIndexes" : true,
 "hidden" : false,
 "priority" : 1,
 "tags" : {
},
 "slaveDelay" : 0,
 "votes" : 1
 }
 ],
 "settings" : {
 "chainingAllowed" : true,
 "heartbeatTimeoutSecs" : 10,
 "getLastErrorModes" : {
},
 "getLastErrorDefaults" : {
 "w" : 1,
 "wtimeout" : 0
 }
 }
 }
 rs0:PRIMARY> use akash
 switched to db akash
 rs0:PRIMARY> db
 akash
 rs0:PRIMARY> db.movie.insert({"name":"tech tutorial"})
 WriteResult({ "nInserted" : 1 })
 
rs0:PRIMARY> show dbs
 akash 0.078GB
 local 1.078GB
rs0:PRIMARY> exit
 bye

 

Check your logs in this open new connections

# tail -f /var/log/mongodb.log
 2015-06-26T04:04:13.323+0530 I NETWORK [conn6] end connection 192.168.42.142:45804 (1 connection now open)
 2015-06-26T04:04:13.324+0530 I NETWORK [initandlisten] connection accepted from 192.168.42.142:45805 #7 (2 connections now open)
 2015-06-26T04:04:18.136+0530 I INDEX [conn1] allocating new ns file /DATA/akash.ns, filling with zeroes...
 2015-06-26T04:04:18.265+0530 I STORAGE [FileAllocator] allocating new datafile /DATA/akash.0, filling with zeroes...
 2015-06-26T04:04:18.267+0530 I STORAGE [FileAllocator] done allocating datafile /DATA/akash.0, size: 64MB, took 0.001 secs
 2015-06-26T04:04:18.276+0530 I WRITE [conn1] insert akash.movie query: { _id: ObjectId('558c81ea839b14ed7d7942f8'), name: "tech tutorials" } ninserted:1 keyUpdates:0 writeConflicts:0 numYields:0 locks:{ Global: { acquireCount: { r: 4, w: 4 } }, MMAPV1Journal: { acquireCount: { w: 8 } }, Database: { acquireCount: { w: 3, W: 1 } }, Collection: { acquireCount: { W: 1 } }, Metadata: { acquireCount: { W: 4 } }, oplog: { acquireCount: { w: 2 } } } 140ms
 2015-06-26T04:04:18.277+0530 I COMMAND [conn1] command akash.$cmd command: insert { insert: "movie", documents: [ { _id: ObjectId('558c81ea839b14ed7d7942f8'), name: "tech tutorials" } ], ordered: true } keyUpdates:0 writeConflicts:0 numYields:0 reslen:80 locks:{ Global: { acquireCount: { r: 4, w: 4 } }, MMAPV1Journal: { acquireCount: { w: 8 } }, Database: { acquireCount: { w: 3, W: 1 } }, Collection: { acquireCount: { W: 1 } }, Metadata: { acquireCount: { W: 4 } }, oplog: { acquireCount: { w: 2 } } } 263ms

Now you go to Second machine and login to mongo shell

# mongo mongodmaster.com:30004

So if any time your master server or Primary is stop or power failure this secondary server become Primary or master automatically.
If you want to add more member in your replSet then you should Proceed further in this Document and these operation perform only Primary server

rs0:SECONDARY>
rs.add("mongodmaster.com:30002")
 { "ok" : 1 }
 
rs0:PRIMARY> rs.conf()
 {
 "_id" : "rs0",
 "version" : 3,
 "members" : [
 {
 "_id" : 0,
 "host" : "mongodslave2.com:30003",
 "arbiterOnly" : false,
 "buildIndexes" : true,
 "hidden" : false,
 "priority" : 1,
 "tags" : {
},
 "slaveDelay" : 0,
 "votes" : 1
 },
 {
 "_id" : 1,
 "host" : "mongodmaster.com:30004",
 "arbiterOnly" : false,
 "buildIndexes" : true,
 "hidden" : false,
 "priority" : 1,
 "tags" : {

},
 "slaveDelay" : 0,
 "votes" : 1
 },
 {
 "_id" : 2,
 "host" : "mongodmaster.com:30002",
 "arbiterOnly" : false,
 "buildIndexes" : true,
 "hidden" : false,
 "priority" : 1,
 "tags" : {

},
 "slaveDelay" : 0,
 "votes" : 1
 }
 ],
 "settings" : {
 "chainingAllowed" : true,
 "heartbeatTimeoutSecs" : 10,
 "getLastErrorModes" : {

},
 "getLastErrorDefaults" : {
 "w" : 1,
 "wtimeout" : 0
 }
 }
 }

rs0:PRIMARY> rs.conf()
 {
 "_id" : "rs0",
 "version" : 2,
 "members" : [
 {
 "_id" : 0,
 "host" : "mongodslave2.com:30003",
 "arbiterOnly" : false,
 "buildIndexes" : true,
 "hidden" : false,
 "priority" : 1,
 "tags" : {
},
 "slaveDelay" : 0,
 "votes" : 1
 },
 {
 "_id" : 1,
 "host" : "mongodmaster.com:30004",
 "arbiterOnly" : false,
 "buildIndexes" : true,
 "hidden" : false,
 "priority" : 1,
 "tags" : {
},
 "slaveDelay" : 0,
 "votes" : 1
 }
 ],
 "settings" : {
 "chainingAllowed" : true,
 "heartbeatTimeoutSecs" : 10,
 "getLastErrorModes" : {
},
 "getLastErrorDefaults" : {
 "w" : 1,
 "wtimeout" : 0
 }
 }
 }
 
rs0:PRIMARY> use akash
 switched to db akash
 
rs0:PRIMARY> db
 akash
 
rs0:PRIMARY> db.movie.insert({"name":"tutorials point"})
 WriteResult({ "nInserted" : 1 })
 
rs0:PRIMARY> show dbs
 akash 0.078GB
 local 1.078GB
 
rs0:PRIMARY> exit
 bye

Check your logs in this open new connections

[root@TechTutorial ~]# tail -f /var/log/mongodb.log
 2015-06-26T04:04:13.323+0530 I NETWORK [conn6] end connection 192.168.42.142:45804 (1 connection now open)
 2015-06-26T04:04:13.324+0530 I NETWORK [initandlisten] connection accepted from 192.168.42.142:45805 #7 (2 connections now open)
 2015-06-26T04:04:18.136+0530 I INDEX [conn1] allocating new ns file /DATA/akash.ns, filling with zeroes...
 2015-06-26T04:04:18.265+0530 I STORAGE [FileAllocator] allocating new datafile /DATA/akash.0, filling with zeroes...
 2015-06-26T04:04:18.267+0530 I STORAGE [FileAllocator] done allocating datafile /DATA/akash.0, size: 64MB, took 0.001 secs
 2015-06-26T04:04:18.276+0530 I WRITE [conn1] insert akash.movie query: { _id: ObjectId('558c81ea839b14ed7d7942f8'), name: "tech tutorials" } ninserted:1 keyUpdates:0 writeConflicts:0 numYields:0 locks:{ Global: { acquireCount: { r: 4, w: 4 } }, MMAPV1Journal: { acquireCount: { w: 8 } }, Database: { acquireCount: { w: 3, W: 1 } }, Collection: { acquireCount: { W: 1 } }, Metadata: { acquireCount: { W: 4 } }, oplog: { acquireCount: { w: 2 } } } 140ms
 2015-06-26T04:04:18.277+0530 I COMMAND [conn1] command akash.$cmd command: insert { insert: "movie", documents: [ { _id: ObjectId('558c81ea839b14ed7d7942f8'), name: "tech tutorials" } ], ordered: true } keyUpdates:0 writeConflicts:0 numYields:0 reslen:80 locks:{ Global: { acquireCount: { r: 4, w: 4 } }, MMAPV1Journal: { acquireCount: { w: 8 } }, Database: { acquireCount: { w: 3, W: 1 } }, Collection: { acquireCount: { W: 1 } }, Metadata: { acquireCount: { W: 4 } }, oplog: { acquireCount: { w: 2 } } } 263ms

 

Now you go to Second machine and login to mongo shell

# mongo mongodmaster.com:30004
 rs0:SECONDARY>
 So if any time your master server or Primary is stop or powerfailure this secondary server become Primary or master automatically.
 If you want to add more member in your replSet then you should Proceed further in this Document and these operation perform only Primary server
 rs.add("mongodmaster.com:30002")
 { "ok" : 1 }
rs0:PRIMARY> rs.conf()
 {
 "_id" : "rs0",
 "version" : 3,
 "members" : [
 {
 "_id" : 0,
 "host" : "mongodslave2.com:30003",
 "arbiterOnly" : false,
 "buildIndexes" : true,
 "hidden" : false,
 "priority" : 1,
 "tags" : {
},
 "slaveDelay" : 0,
 "votes" : 1
 },
 {
 "_id" : 1,
 "host" : "mongodmaster.com:30004",
 "arbiterOnly" : false,
 "buildIndexes" : true,
 "hidden" : false,
 "priority" : 1,
 "tags" : {

},
 "slaveDelay" : 0,
 "votes" : 1
 },
 {
 "_id" : 2,
 "host" : "mongodmaster.com:30002",
 "arbiterOnly" : false,
 "buildIndexes" : true,
 "hidden" : false,
 "priority" : 1,
 "tags" : {
},
 "slaveDelay" : 0,
 "votes" : 1
 }
 ],
 "settings" : {
 "chainingAllowed" : true,
 "heartbeatTimeoutSecs" : 10,
 "getLastErrorModes" : {
},
 "getLastErrorDefaults" : {
 "w" : 1,
 "wtimeout" : 0
 }
 }
 }



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