MongoDB学习资料五---MongoDB的sharding功能(转)
MongoDB的auto-sharding功能是指mongodb通过mongos自动建立一个水平扩展的数据库集群系统，将数据库分表存储在sharding的各个节点上。一个mongodb集群包括一些shards（包括一些mongod进程），mongos路由进程，一个或多个config服务器
Shards
每一个shard包括一个或多个服务和存储数据的mongod进程（mongod是MongoDB数据的核心进程）
典型的每个shard开启多个服务来提高服务的可用性。这些服务/mongod进程在shard中组成一个复制集
Chunks
Chunk是一个来自特殊集合中的一个数据范围，（collection，minKey，maxKey）描叙一个chunk，它介于minKey和maxKey范围之间。
例如chunks 的maxsize大小是100M，如果一个文件达到或超过这个范围时，会被切分到2个新的chunks中。当一个shard的数据过量时，chunks将会被迁移到其他的shards上。同样，chunks也可以迁移到其他的shards上
Config Servers
Config服务器存储着集群的metadata信息，包括每个服务器，每个shard的基本信息和chunk信息
Config服务器主要存储的是chunk信息。每一个config服务器都复制了完整的chunk信息。
配置：（模拟2个shard服务和一个config服务）
Shard1：27020
Shard2：27021
Config：27022
Mongos启动时默认使用的27017端口
新建存放数据的目录 CODE:
$ mkdir 27020 27021 27022
$ ls
270202702127022
$ ./mongod --dbpath /home/falcon/mongodata/27020 --port 27020 > /home/falcon/mongodata/27020.log &
$ ./mongod --dbpath /home/falcon/mongodata/27021 --port 27021> /home/falcon/mongodata/27021.log &
$ ./mongod --dbpath /home/falcon/mongodata/27022 --port 27022> /home/falcon/mongodata/27022.log &启动mongos时，默认开启了27017端口 CODE:
$ ./mongos --configdb localhost:27022 > /home/falcon/mongodata/config.log &检查是否启动 CODE:
$ ps -ef|grep mongo
falcon 2612 10 20:15 ? 00:00:00 ./mongod --dbpath /home/falcon/mongodata/27020 --port 27020
falcon 2619 10 20:15 ? 00:00:00 ./mongod --dbpath /home/falcon/mongodata/27021 --port 27021
falcon 2625 10 20:15 ? 00:00:00 ./mongod --dbpath /home/falcon/mongodata/27022 --port 27022
falcon 2658 10 20:15 ? 00:00:00 ./mongos --configdb localhost:27022
falcon 280427720 20:31 pts/0 00:00:00 bin/mongo
falcon 284728120 20:55 pts/2 00:00:00 grep mongo
$
$ netstat -an-t
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address Foreign Address State
tcp 0 0 0.0.0.0:10022 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:27017 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:587 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:27020 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:27021 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:27022 0.0.0.0:* LISTEN
......
tcp 0 0 0.0.0.0:28020 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:28021 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:28022 0.0.0.0:* LISTEN
tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN
........看到以上信息证明mongodb启动完整，对于开启的28020、28021、28022是对于的http接口 CODE:
$ ./mongo 默认连接到mongos上
MongoDB shell version: 1.2.4-
url: test
connecting to: test
type "help" for help
> show dbs
admin
config
Local加入shard节点 CODE:
> use admin
switched to db admin
> db.runCommand( { addshard : "localhost:27020", allowLocal : true } )
{"ok" : 1 , "added" : "localhost:27020"}
> db.runCommand( { addshard : "localhost:27021", allowLocal : true } )
{"ok" : 1 , "added" : "localhost:27021"}
> db.runCommand({listshards:1}); 查看shard节点列表
{
"shards" : [
{
"_id" : ObjectId("4b9cd380c33000afad27718e"),
"host" : "localhost:27020"
},
{
"_id" : ObjectId("4b9cd381c33000afad27718f"),
"host" : "localhost:27021"
}
],
"ok" : 1
}新建自动切片的库user001： CODE:
> config = connect("localhost:27022")
> config = config.getSisterDB("config")
> user001=db.getSisterDB("user001");
user001
> db.runCommand({enablesharding:"user001"})
{ "ok" : 1 }
> db.printShardingStatus();
--- Sharding Status ---
sharding version: { "_id" : ObjectId("4b9cd354c33000afad27718d"), "version" : 2 }
shards:
{ "_id" : ObjectId("4b9cd380c33000afad27718e"), "host" : "localhost:27020" }
{ "_id" : ObjectId("4b9cd381c33000afad27718f"), "host" : "localhost:27021" }
databases:
{ "name" : "admin", "partitioned" : false, "primary" : "localhost:27022", "_id" : ObjectId("4b9cd3776693dcfa468dec13") }
{ "name" : "user001", "partitioned" : true, "primary" : "localhost:27021", "_id" : ObjectId("4b9cde866693dcfa468dec17") }
my chunks我们来在user001中新建表，插入数据 CODE:
> use user001
switched to db user001
> db.createCollection("user_001")
{ "ok" : 1 }
> show collections
system.indexes
user_001
> db.user_001.insert({uid:1,username:"Falcon.C",sex:"男",age:25});
> db.user_001.find();
{ "_id" : ObjectId("4b9ce1a6c84d7f20576c4df1"), "uid" : 1, "username" : "Falcon.C", "sex" : "男", "age" : 25 }我们来看看user001库被分配到了哪个shard上 CODE:
$ ls -R
.:
270202702127022mongos.log
./27020:
27020.logmongod.locktest.0test.1test.ns_tmp
./27020/_tmp:
./27021:
27021.logmongod.lock_tmpuser.0user001.0user001.1user001.nsuser.1user.ns
./27021/_tmp:
./27022:
27022.logconfig.0config.nsmongod.lockmongos.log_tmp
./27022/_tmp:
$从以上的文件可以看出，user001被分配到了27021的shard上了，但是通过mongos路由，我们并感觉不到是数据存放在哪个shard的chunk上
Sharding的管理命令 CODE:
> db.$cmd.findOne({isdbgrid:1});
{ "isdbgrid" : 1, "hostname" : "www.fwphp.cn", "ok" : 1 }
> db.$cmd.findOne({ismaster:1});
{ "ismaster" : 1, "msg" : "isdbgrid", "ok" : 1 }
> printShardingStatus(db.getSisterDB("config"))
--- Sharding Status ---
sharding version: { "_id" : ObjectId("4b9cd354c33000afad27718d"), "version" : 2 }
shards:
{ "_id" : ObjectId("4b9cd380c33000afad27718e"), "host" : "localhost:27020" }
{ "_id" : ObjectId("4b9cd381c33000afad27718f"), "host" : "localhost:27021" }
databases:
{ "name" : "admin", "partitioned" : false, "primary" : "localhost:27022", "_id" : ObjectId("4b9cd3776693dcfa468dec13") }
my chunks
{ "name" : "user001", "partitioned" : true, "primary" : "localhost:27021", "_id" : ObjectId("4b9cde866693dcfa468dec17") }
my chunks
> use admin
switched to db admin
> db.runCommand({netstat:1})
{ "configserver" : "localhost:27022", "isdbgrid" : 1, "ok" : 1 }
>参考信息：http://www.mongodb.org/display/DOCS/Sharding
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