MongoDB分片

分片（sharding）是將資料拆分，將其分散在不同的機器上的過程。MongoDB支援自動分片

片鍵（shard key）設定分片時，需要從集合裡面選一個鍵，用該鍵作為資料拆分的依據，此鍵就叫片鍵

分片一般有以下三部分組成：

片     可以是普通的mongod程式，也可以是副本集。

但是即使一片內有多臺伺服器，也只能有一個主伺服器，其他的伺服器儲存相同的資料

         Mongos

                  就是mongodb的路由器程式，它路由所有請求，然後將結果聚合。它不儲存儲存資料或配置資訊

                   它本身並不儲存資料或配置資訊（但會快取配置伺服器資訊）

         配置伺服器

                   儲存叢集的配置資訊：資料和片的對應關係

                   Mongos不會永久存放資料,所以需要個地方存放分片配置

環境規劃

	Dbpath	logpath	port	備註
1	/data/mongodb/conf	/data/mongodb/logs/conf.log	10000	配置伺服器
2	——	/data/mongodb/logs/mongos.log	20000	mongos
3	/data/mongodb/shard1	/data/mongodb/logs/shard1.log	30000	分片1
4	/data/mongodb/shard2	/data/mongodb/logs/shard2.log	40000	分片2

建立db|logpath目錄

~]# mkdir /data/mongodb/conf /data/mongodb/shard{1,2}

~]# mkdir /data/mongodb/logs/

啟動配置服務

#配置伺服器要最先啟動，因為mongos會用它其上的配置資訊

~]# mongod --dbpath /data/mongodb/conf --logpath /data/mongodb/logs/conf.log --logappend --fork --port 10000

about to fork child process, waiting until server is ready for connections.

forked process: 14234

child process started successfully, parent exiting

啟動路由服務

#mongos程式不需要資料目錄

~]# mongos --port 20000 --configdb 192.168.211.217:10000 --logpath /data/mongodb/logs/mongos.log  --logappend --fork

2015-01-15T17:21:13.758+0800 warning: running with 1 config server should be done only for testing purposes and is not recommended for production

about to fork child process, waiting until server is ready for connections.

forked process: 15361

child process started successfully, parent exiting

啟動分片服務

~]#mongod --fork --dbpath /data/mongodb/shard1 --logpath /data/mongodb/logs/shard1.log --logappend -port 30000

about to fork child process, waiting until server is ready for connections.

forked process: 15426

child process started successfully, parent exiting

~]#mongod --fork --dbpath /data/mongodb/shard2 --logpath /data/mongodb/logs/shard2.log --logappend -port 40000

about to fork child process, waiting until server is ready for connections.

forked process: 15515

child process started successfully, parent exiting

新增分片

#檢視mongos的埠

~]# netstat  -ntpl|grep mongos

tcp        0      0 0.0.0.0:20000               0.0.0.0:*                   LISTEN      15361/mongos

#連線剛才啟動的mongos（192.168.211.217:20000）

~]# /usr/local/mongodb/bin/mongo --port 20000

MongoDB shell version: 2.6.6

connecting to: 127.0.0.1:20000/test

#確認是連線下mongos了

mongos> use admin

switched to db admin

mongos> db.runCommand({addshard:"192.168.211.217:30000",allowLocal:true })

{ "shardAdded" : "shard0000", "ok" : 1 }

mongos> db.runCommand({addshard:"192.168.211.217:40000",allowLocal:true })

{ "shardAdded" : "shard0001", "ok" : 1 }

注：allowLocal:true當路由程式和分片在同一臺機器上要指定allowLocal為true

#進入mongos程式config庫可以看到目前分片的情況

mongos> use config

switched to db config

mongos> db.shards.find()

{ "_id" : "shard0000", "host" : "192.168.211.217:30000" }

{ "_id" : "shard0001", "host" : "192.168.211.217:40000" }

切分資料

預設的是不會將儲存的每條資料進行分片處理，需要在資料庫和集合的粒度上都開啟分片功能

#資料庫級別開啟分片

#開啟test庫的分片功能

~]# /usr/local/mongodb/bin/mongo --port 20000

MongoDB shell version: 2.6.6

connecting to: 127.0.0.1:20000/test

mongos> use admin

switched to db admin

mongos> db.runCommand({"enablesharding":"test"})

{ "ok" : 1 }

#連線test庫長生測試資料emp集合

mongos> use test

switched to db test

。。。。。。。

mongos> db.emp.find();

{ "_id" : ObjectId("54b78bb75cb5db3323e5e57b"), "empno" : 7369, "ENAME" : "SMITH", "JOB" : "CLERK", "MGR" : 7902, "SAL" : 800 }

{ "_id" : ObjectId("54b78bb95cb5db3323e5e57c"), "empno" : 7499, "ENAME" : "ALLEN", "JOB" : "SALESMAN", "MGR" : 7698, "SAL" : 1600 }

{ "_id" : ObjectId("54b78bb95cb5db3323e5e57d"), "empno" : 7521, "ENAME" : "WARD", "JOB" : "SALESMAN", "MGR" : 7698, "SAL" : 1250 }

{ "_id" : ObjectId("54b78bb95cb5db3323e5e57e"), "empno" : 7566, "ENAME" : "JONES", "JOB" : "MANAGER", "MGR" : 7839, "SAL" : 2975 }

{ "_id" : ObjectId("54b78bb95cb5db3323e5e57f"), "empno" : 7654, "ENAME" : "MARTIN", "JOB" : "SALESMAN", "MGR" : 7698, "SAL" : 1250 }

{ "_id" : ObjectId("54b78bb95cb5db3323e5e580"), "empno" : 7698, "ENAME" : "BLAKE", "JOB" : "MANAGER", "MGR" : 7839, "SAL" : 2850 }

{ "_id" : ObjectId("54b78bb95cb5db3323e5e581"), "empno" : 7782, "ENAME" : "CLARK", "JOB" : "MANAGER", "MGR" : 7839, "SAL" : 2450 }

{ "_id" : ObjectId("54b78bb95cb5db3323e5e582"), "empno" : 7788, "ENAME" : "SCOTT", "JOB" : "ANALYST", "MGR" : 7566, "SAL" : 3000 }

{ "_id" : ObjectId("54b78bb95cb5db3323e5e583"), "empno" : 7788, "ENAME" : "SCOTT", "JOB" : "ANALYST", "MGR" : 7566, "SAL" : 3000 }

{ "_id" : ObjectId("54b78bb95cb5db3323e5e584"), "empno" : 7844, "ENAME" : "TURNER", "JOB" : "SALESMAN", "MGR" : 7698, "SAL" : 1500 }

{ "_id" : ObjectId("54b78bb95cb5db3323e5e585"), "empno" : 7876, "ENAME" : "ADAMS", "JOB" : "CLERK", "MGR" : 7788, "SAL" : 1100 }

{ "_id" : ObjectId("54b78bb95cb5db3323e5e586"), "empno" : 7900, "ENAME" : "JAMES", "JOB" : "CLERK", "MGR" : 7698, "SAL" : 950 }

{ "_id" : ObjectId("54b78bb95cb5db3323e5e587"), "empno" : 7902, "ENAME" : "FORD", "JOB" : "ANALYST", "MGR" : 7566, "SAL" : 3000 }

{ "_id" : ObjectId("54b78bb95cb5db3323e5e588"), "empno" : 7934, "ENAME" : "MILLER", "JOB" : "CLERK", "MGR" : 7782, "SAL" : 1300 }

#對集合進行分片（shardcollection）

mongos> use admin

switched to db admin

mongos> db.runCommand({"shardcollection":"test.emp","key":{"_id":1}})

{ "collectionsharded" : "test.emp", "ok" : 1 }

mongos> use config

switched to db config

mongos> db.databases.find()

{ "_id" : "admin", "partitioned" : false, "primary" : "config" }

{ "_id" : "test", "partitioned" : true, "primary" : "shard0000" }

#“_id”,字串。表示資料庫名。

“ partioned”,布林型。如果為true則表示開啟了分片功

“primary”，字串。這個值與“_id”對應表示這個資料庫的“大本營“在哪裡

mongos> db.collections.find()

{ "_id" : "test.emp", "lastmod" : ISODate("2015-01-15T09:48:49.919Z"), "dropped" : false, "key" : { "_id" : 1 }, "unique" : false, "lastmodEpoch" : ObjectId("54b78d0167f270682893cda6") }

mongos> db.chunks.find()

{ "_id" : "test.emp-_id_MinKey", "lastmod" : Timestamp(1, 0), "lastmodEpoch" : ObjectId("54b78d0167f270682893cda6"), "ns" : "test.emp", "min" : { "_id" : { "$minKey" : 1 } }, "max" : { "_id" : { "$maxKey" : 1 } }, "shard" : "shard0000" }

#這樣emp集合就按照“_id”分片了，再新增資料，就會依據“_id”片鍵分散到各個片上

檢視分片情況

mongos> sh.status()

--- Sharding Status ---

  sharding version: {

        "_id" : 1,

        "version" : 4,

        "minCompatibleVersion" : 4,

        "currentVersion" : 5,

        "clusterId" : ObjectId("54b7865f648316c44268333c")

}

  shards:

        {  "_id" : "shard0000",  "host" : "192.168.211.217:30000" }

        {  "_id" : "shard0001",  "host" : "192.168.211.217:40000" }

  databases:

        {  "_id" : "admin",  "partitioned" : false,  "primary" : "config" }

        {  "_id" : "test",  "partitioned" : true,  "primary" : "shard0000" }

                test.emp

                        shard key: { "_id" : 1 }

                        chunks:

                                shard0000       1

                        { "_id" : { "$minKey" : 1 } } --&gt> { "_id" : { "$maxKey" : 1 } } on : shard0000 Timestamp(1, 0)