[MongoDB] Replication and Repica Sets 만들기

MongoDB의 Replica Set을 만들어 보자. 먼저 Master/Slave와 Primary/Secondary 순으로 본다. Master/Slave는 Slave에서 Read가 된다. 그러나 Primary/Secondary에서 Secondary는 Read도 되지 않는다.  

1. Replica Set 만들기 위한 Master / Slave 에 대해 알아보자. (Replica Set은 아니다)

  - Master로 DB 수행하기 : master의 mongo에서 CRUD 가능

$ ./mongod -dbpath /home/dowon/MongoDB/db01 --master &

만일 db가 비정상 종료되었다면 

$ ./mongod -dbpath /home/dowon/MongoDB/db01 --master --repair &

수행후에 다시 $ ./mongod -dbpath /home/dowon/MongoDB/db01 --master & 를 수행한다. 

... 하기 메세지 나오면 정상 부팅

Fri Jan  4 19:29:59 [initandlisten] Unable to check for journal files due to: boost::filesystem::basic_directory_iterator constructor: No such file or directory: "/home/dowon/MongoDB/db01/journal"

Fri Jan  4 19:29:59 [initandlisten] waiting for connections on port 27017

Fri Jan  4 19:29:59 [websvr] admin web console waiting for connections on port 28017

   

  - Slave로 DB 수행하기 : -slave 옵션 

    + slave의 mongo에서 CUD 안됨. Read만 가능하다. 

    + source 지정하여 replica set 만들 master가 누구인지 알려준다. 

    + 기존에 single로 사용하던 mongod를 master/slave로 묶고자 할 경우 기존 데이터를 slave로 복제하기 잘 안됨

       -> 다른 디렉토리로 복사해서 그런가? 테스트 필요함

    + 신규로 master/slave를 띄워서 save 또는 insert 하였을 때 slave 쪽 디렉토리에 db 파일이 제대로 복제됨 

$ ./mongod --dbpath /home/dowon/MongoDB/db02 --port 27018 --slave --source localhost:27017 &

...

Fri Jan  4 19:12:46 [initandlisten] Unable to check for journal files due to: boost::filesystem::basic_directory_iterator constructor: No such file or directory: "/home/dowon/MongoDB/db02/journal"

Fri Jan  4 19:12:46 [initandlisten] waiting for connections on port 27018   <-- 정상 부팅

Fri Jan  4 19:12:46 [websvr] admin web console waiting for connections on port 28018

// 하기 메세지는 master에 있는 데이터 파일을 slave로 복사해 온다. 마치 git의 pull과 유사한 느낌 ^^ 

Fri Jan  4 19:12:47 [FileAllocator] done allocating datafile /home/dowon/MongoDB/db02/local.ns, size: 16MB,  took 0.001 secs

Fri Jan  4 19:12:48 [FileAllocator] allocating new datafile /home/dowon/MongoDB/db02/local.0, filling with zeroes...

Fri Jan  4 19:12:48 [replslave] build index done.  scanned 0 total records. 0 secs

// db02 디렉토리에 가보면 db01에 있던 데이터베이스 mydb가 copy되어 있는 것을 볼 수 있다. 

Fri Jan  4 19:12:48 [replslave] resync: dropping database mydb

Fri Jan  4 19:12:48 [replslave] resync: cloning database mydb to get an initial copy

Fri Jan  4 19:12:48 [FileAllocator] allocating new datafile /home/dowon/MongoDB/db02/mydb.ns, filling with zeroes...

Fri Jan  4 19:12:48 [FileAllocator] done allocating datafile /home/dowon/MongoDB/db02/mydb.ns, size: 16MB,  took 0.045 secs

Fri Jan  4 19:12:49 [replslave] resync: done with initial clone for db: mydb

Fri Jan  4 19:12:49 [FileAllocator] done allocating datafile /home/dowon/MongoDB/db02/mydb.1, size: 32MB,  took 0.085 secs

2. Replica Set default 만들기 

  - replica set 구동하기 : db11, db12, db13 3개를 띄운다. replica set 명칭은 dowon01 이다. 

  - 디렉토리를 3개 만들고 각 디렉토리별로 서로 다른 port로 replica set 1개를 만들어 본다.

  - mongod를 shutdown 시키고 싶을 경우 : mongo 쉘에서 db.shutdownServer({timeoutSecs: 60});  - 메뉴얼

  - 결론 : mongod를 여러개 띄워서 파일시스템의 약점을 극복한다 (High Availability - HA 구성)

//////////////////////////////////////

// Replica Set 을 1개 만든다 

$ ./mongod --replSet dowon01 --port 30000 --dbpath /home/dowon/MongoDB/db11

$ ./mongod --replSet dowon01 --port 40000 --dbpath /home/dowon/MongoDB/db12

$ ./mongod --replSet dowon01 --port 50000 --dbpath /home/dowon/MongoDB/db13

// 하기 환경설정관련 에러가 나온다 (정상 - 아직 환경설정 안했기 때문에 ^^)

... 중략 ...

Fri Jan 25 23:14:06 [rsStart] replSet can't get local.system.replset config from self or any seed (EMPTYCONFIG)

Fri Jan 25 23:14:23 [initandlisten] connection accepted from 127.0.0.1:34440 #1 (1 connection now open)

Fri Jan 25 23:14:26 [rsStart] replSet can't get local.system.replset config from self or any seed (EMPTYCONFIG)

/////////////////////////////////////

// mongo client 접속 하기

[dowon@localhost mongodb]$ ./mongo localhost:30000

MongoDB shell version: 2.2.2

connecting to: localhost:30000/test

> show dbs

local (empty)

> exit

bye

[dowon@localhost mongodb]$ ./mongo localhost:40000

MongoDB shell version: 2.2.2

connecting to: localhost:40000/test

> show dbs

local (empty)

> exit

bye

[dowon@localhost mongodb]$ ./mongo localhost:50000

MongoDB shell version: 2.2.2

connecting to: localhost:50000/test

> show dbs

local (empty)

  - Configuration 작업하기 

///////////////////////////////////////////////////

// PRIMARY + SECONDARY Replica Set 만들기 

[dowon@localhost mongodb]$ ./mongo localhost:30000

MongoDB shell version: 2.2.2

connecting to: localhost:30000/test

> var config={_id:'dowon01', members:[{_id:0, host:30000},

... {_id:1, host:40000}^C

// 환경 객체를 만든다 

> var config={_id:'dowon01', members:[

    {_id:0, host:'localhost:30000'},

    {_id:1, host:'localhost:40000'},

    {_id:2, host:'localhost:50000'}]

  }

// replica set을 초기화 한다. 

> rs.initiate(config);

{

"info" : "Config now saved locally.  Should come online in about a minute.",

"ok" : 1

}

// 3000 port의 메세지를 보면 다음과 같다. 

// 1) config 없을 때 나오는 메세지이다. 

Fri Jan  4 21:20:29 [rsStart] replSet can't get local.system.replset config from self or any seed (EMPTYCONFIG)

Fri Jan  4 21:20:39 [rsStart] replSet can't get local.system.replset config from self or any seed (EMPTYCONFIG)

// 2) rs.initiate를 수행하면 하기와 같은 메세지가 나온다. 

Fri Jan  4 21:20:44 [conn2] replSet replSetInitiate admin command received from client

Fri Jan  4 21:20:44 [conn2] replSet replSetInitiate config object parses ok, 3 members specified

Fri Jan  4 21:20:44 [conn2] replSet replSetInitiate all members seem up

Fri Jan  4 21:20:44 [conn2] ******

Fri Jan  4 21:20:44 [conn2] replSet info saving a newer config version to local.system.replset

Fri Jan  4 21:20:44 [conn2] replSet saveConfigLocally done

Fri Jan  4 21:20:44 [conn2] replSet replSetInitiate config now saved locally.  Should come online in about a minute.

Fri Jan  4 21:20:44 [conn2] command admin.$cmd command: { replSetInitiate: { _id: "dowon01", members: [ { _id: 0.0, host: "localhost:30000" }, { _id: 1.0, host: "localhost:40000" }, { _id: 2.0, host: "localhost:50000" } ] } } ntoreturn:1 keyUpdates:0 locks(micros) W:431969 reslen:112 477ms

Fri Jan  4 21:20:49 [rsStart] replSet I am localhost:30000

Fri Jan  4 21:20:49 [rsStart] replSet STARTUP2

Fri Jan  4 21:20:49 [rsHealthPoll] replSet member localhost:40000 is up

Fri Jan  4 21:20:49 [rsHealthPoll] replSet member localhost:50000 is up

Fri Jan  4 21:20:50 [initandlisten] connection accepted from 127.0.0.1:43880 #3 (2 connections now open)

Fri Jan  4 21:20:50 [rsSync] replSet SECONDARY

... 중략 ...

>                                   <== enter key를 치면 하기와 같은 프롬프트로 자동 변경된다

dowon01:PRIMARY>   <== "replicaSet명칭:PRIMARY>" 명칭이 나온다 

////////////////////////////////////////////

// 40000, 50000 번의 client를 들어가 보자 

[dowon@localhost mongodb]$ ./mongo localhost:40000

MongoDB shell version: 2.2.2

connecting to: localhost:40000/test

dowon01:SECONDARY> 

[dowon@localhost mongodb]$ ./mongo localhost:50000

MongoDB shell version: 2.2.2

connecting to: localhost:50000/test

dowon01:SECONDARY> 

//////////////////////////////////////////

// SECONDARY 에서 하기와같은 에러 발생시 rs.slaveOk() 수행

[mongodb@localhost ~]$ ./mongo localhost:40000

MongoDB shell version: 2.2.2

connecting to: localhost:20000/test

dowon01:SECONDARY> show dbs

dowonDB 0.0625GB

local 0.125GB

test (empty)

dowon01:SECONDARY> use dowonDB

switched to db dowonDB

dowon01:SECONDARY> db

dowonDB

dowon01:SECONDARY> show collections

Fri Jan 25 23:45:06 uncaught exception: error: { "$err" : "not master and slaveOk=false", "code" : 13435 }

// primary 의 데이터를 가져온다

dowon01:SECONDARY> rs.slaveOk()

dowon01:SECONDARY> show collections

test

system.indexes

//////////////////////////////////////////

// PRIMARY 에서 데이터베이스 생성하기 

dowon01:PRIMARY> db

test

dowon01:PRIMARY> use peopleDB

switched to db peopleDB

dowon01:PRIMARY> db.people.insert({_id:1, age:11, name:'dowon1', sex:false});

dowon01:PRIMARY> db.people.insert({_id:2, age:22, name:'dowon2', sex:true});

dowon01:PRIMARY> db.people.insert({_id:3, age:33, name:'dowon3', sex:false});

dowon01:PRIMARY> db.people.find();

{ "_id" : 1, "age" : 11, "name" : "dowon1", "sex" : false }

{ "_id" : 2, "age" : 22, "name" : "dowon2", "sex" : true }

{ "_id" : 3, "age" : 33, "name" : "dowon3", "sex" : false }

////////////////////////////////////////////////////////////////////////

// SECONDARY에서 데이터베이스를 READ해 보면 에러가 발생한다

// Replica Set의 Secondary는 Slave가 아니기 때문에 사용할 수 없다. 

// 즉, Primary가 down 되어야 사용 가능하다.

// 단, 1)의 Master/Slave 구조에서 Slave는 READ가 가능하다.

[dowon@localhost mongodb]$ ./mongo localhost:50000

MongoDB shell version: 2.2.2

connecting to: localhost:50000/test

dowon01:SECONDARY> show dbs  // 데이터베이스 보기 

local 0.125GB

peopleDB 0.0625GB

dowon01:SECONDARY> use peopleDB // 해당 데이터베이스로 switching하여 사용하기 

switched to db peopleDB

dowon01:SECONDARY> show collections // 해당 데이터베이스의 테이블(?) 보기 

Fri Jan  4 21:31:59 uncaught exception: error: { "$err" : "not master and slaveOk=false", "code" : 13435 }

dowon01:SECONDARY> db

peopleDB

dowon01:SECONDARY> db.people.find();  // "db"는 peopleDB를 가르키는 포인터

error: { "$err" : "not master and slaveOk=false", "code" : 13435 }

위 명령의 구조는 다음과 같다. (참조 19page)

  - Primary를 종료하면 Sencodary가 Primary로 자동 변경된다

[dowon@localhost mongodb]$ ./mongo localhost:40000

MongoDB shell version: 2.2.2

connecting to: localhost:40000/test

... 중략

dowon01:SECONDARY> show collections

Fri Jan  4 21:31:33 uncaught exception: error: { "$err" : "not master and slaveOk=false", "code" : 13435 }

dowon01:SECONDARY> 

// 30000 port mongoDB를 down시키고 4000 port의 mongo client에서 enter를 치면 하기와 같이 primary로 바뀐다. 

dowon01:PRIMARY> 

// Primary 이므로 CRUD가 가능해 진다. 

dowon01:PRIMARY> show collections

people

system.indexes

dowon01:PRIMARY> db.people.insert({_id:4, age:44, name:'youngsik', sex:true});

dowon01:PRIMARY> db.people.find();

{ "_id" : 1, "age" : 11, "name" : "dowon1", "sex" : false }

{ "_id" : 2, "age" : 22, "name" : "dowon2", "sex" : true }

{ "_id" : 3, "age" : 33, "name" : "dowon3", "sex" : false }

{ "_id" : 4, "age" : 44, "name" : "youngsik", "sex" : true }

/////////////////////////////////////////////////////////////////////

// 다시 30000 port를 기동시키고, 3000 port client로 접속한다.

// 40000 port가 그대로 Primary로 존재하고, 30000 port는 Secondary로 된다. 

i Jan  4 21:42:46 trying reconnect to localhost:30000

Fri Jan  4 21:42:46 reconnect localhost:30000 ok

dowon01:SECONDARY> 

3) Replca Set 기본과 Master/Slave를 결합한 형태

   * 참조 20page

< 참조 > 

- High Availabiltity & Replica Sets with mongoDB

http://www.slideshare.net/shaolintiger/high-availabiltity-replica-sets-with-mongodb

- Sharding by mongodb/10gen on Nov 28, 2012

http://www.slideshare.net/mongodb/sharding-15392976

- Sharding morning session

http://www.slideshare.net/mongodb/sharding-morning-session

- Sharding - Seoul 2012

http://www.slideshare.net/mongodb/sharding-seoul-2012-15576057

- Replication and Replica Sets

http://www.slideshare.net/mongodb/replication-and-replica-sets-tokyo-2012

- MongoDB Basic Concepts

http://www.slideshare.net/mongodb/mongodb-basic-concepts-15674838

- A Morning with MongoDB - Helsinki

http://www.slideshare.net/mongodb/morning-with-mongo-db-helsinki-1

- MongoDB Roadmap

http://www.slideshare.net/mongodb/next-15674517