mongodb的sharding集群由以下3个服务组成：
Shards Server: 每个shard由一个或多个mongod进程组成，用于存储数据
Config Server: 用于存储集群的Metadata信息，包括每个Shard的信息和chunks信息
Route Server: 用于提供路由服务，由Client连接，使整个Cluster看起来像单个DB服务器
另外，Chunks是指MongoDB中一段连续的数据块，默认大小是200M，一个Chunk位于其中一台Shard服务器上
下面，搭建一个Cluster，它由4台服务器组成，包括3个Shard，3个Config，1个Route
搭建mongodb sharding 配置过程
1 创建数据存放目录
/opt/mongodata/r1
/opt/mongodata/r2
/opt/mongodata/r3
--注意配置顺序
rac1
mkdir -p /opt/mongodata/config1
rac2
mkdir -p /opt/mongodata/config2
rac3
mkdir -p /opt/mongodata/config3
rac4
mkdir -p /opt/mongodata/mongos
2 配置config
rac1
[mongodb@rac1 bin]$ ./mongod --configsvr --dbpath=/opt/mongodata/config1 --port 28001 --logpath=/opt/mongodata/config1/config.log &
[1] 19996
[mongodb@rac1 bin]$ all output going to: /opt/mongodata/config1/config.log
rac2
[mongodb@rac2 bin]$ ./mongod --configsvr --dbpath=/opt/mongodata/config2 --port 28002 --logpath=/opt/mongodata/config2/config.log &
[1] 27223
[mongodb@rac2 bin]$ all output going to: /opt/mongodata/config2/config.log
rac3
[mongodb@rac3 bin]$ ./mongod --configsvr --dbpath=/opt/mongodata/config3 --port 28003 --logpath=/opt/mongodata/config3/config.log &
[1] 31020
[mongodb@rac3 bin]$ all output going to: /opt/mongodata/config3/config.log
3 配置路由设置
rac4
[mongodb@rac4 bin]$ ./mongos --chunkSize 1 --configdb "rac1:28001,rac2:28002,rac3:28003" --logpath /opt/mongodata/mongos/mongos.log &
NOTE:mongos 不需要-dbpath
4 配置sharding 节点
rac1
[mongodb@rac1 bin]$ ./mongod -shardsvr -dbpath=/opt/mongodata/r1 -port 27018 -logpath=/opt/mongodata/r1/27018.log &
rac2
[mongodb@rac2 bin]$ ./mongod -shardsvr -dbpath=/opt/mongodata/r2 -port 27019 -logpath=/opt/mongodata/r2/27019.log &
rac3
[mongodb@rac3 bin]$ ./mongod -shardsvr -dbpath=/opt/mongodata/r3 -port 27020 -logpath=/opt/mongodata/r3/27020.log &
5 在路由服务器上进行添加shard配置：
addshard : 添加 Shard Server，相关的命令还有 listshards 和 removeshard。如果是要添加replica set 的shard 其语法是：db.runCommand({addshard:'replica set 的名字/IP:PORT,[IP:PORT,...]'});
enablesharding : 用于设置可以被分布存储的数据库。
激活指定数据库的分片功能，这样数据库中的不同的collections会被分配到不同的shard上面，然而同一个collection会在同一个shard上面。
shardcollection : 用于设置具体被切块的集合名称，且必须指定 Shard Key，系统会自动创建索引。要进行collection级别的shard，必须执行
db.runCommand( { shardcollection : “”,key : });
namespace ： 是collection的名字
shardkeypatternobject：片健，对一个集合进行分片时要设置一个字段或者说键作为拆分的依据。
Note：
1 要进行collection级别的shard 必须先激活数据库级别的shard。
2 Sharded Collection 只能有一个 unique index，且必须是 shard key。
官方文档：a sharded collection can have only one unique index, which must exist on the shard key.NO other unique indexes can exist on the collection.
mongos> db.runCommand({addshard:'10.250.7.225:27018'});
{ "shardAdded" : "shard0000", "ok" : 1 }
mongos> db.runCommand({addshard:'10.250.7.249:27019'});
{ "shardAdded" : "shard0001", "ok" : 1 }
mongos> db.runCommand({addshard:'10.250.7.241:27020'});
{ "shardAdded" : "shard0002", "ok" : 1 }
当然如果是replica set + sharding 架构也可以使用db.runCommand({addshard:'replica set 的名字/IP:PORT,[IP:PORT,...]',name:"shard的名字",maxSize;N});
Name:用于指定每个shard的名字，不指定的话系统将自动分配
maxSize:指定各个shard可使用的最大磁盘空间，单位megabytes
maxSize:指定各个shard可使用的最大磁盘空间，单位megabytes
mongos>
mongos> db.runCommand({"enablesharding": "test"})
{ "ok" : 1 }
mongos> db.runCommand({listshards:1});
{
"shards" : [
{
"_id" : "shard0000",
"host" : "10.250.7.225:27018"
},
{
"_id" : "shard0001",
"host" : "10.250.7.249:27019"
},
{
"_id" : "shard0002",
"host" : "10.250.7.241:27020"
}
],
"ok" : 1
}
mongos> printShardingStatus();
--- Sharding Status ---
sharding version: { "_id" : 1, "version" : 3 }
shards:
{ "_id" : "shard0000", "host" : "10.250.7.225:27018" }
{ "_id" : "shard0001", "host" : "10.250.7.249:27019" }
{ "_id" : "shard0002", "host" : "10.250.7.241:27020" }
databases:
{ "_id" : "admin", "partitioned" : false, "primary" : "config" }
{ "_id" : "test", "partitioned" : true, "primary" : "shard0000" }
mongos> db.runCommand({shardcollection:'test.yql',key:{_id:1}, unique : true});
{ "collectionsharded" : "test.yql", "ok" : 1 }
mongos> use test
switched to db test
mongos>
mongos> db.yql.insert({id:1,val:"this is a message on rac4 mongos !"});
mongos> db.yql.insert({id:2,val:"this is a message on rac4:27020 --2011-11-02 9:47!"});
mongos> db.yql.insert({id:2,val:"this is a message on rac4:27020 --2011-11-02 9:49!"});
mongos> db.yql.insert({id:3,val:"this is a message on rac4:27020 --2011-11-02 9:50!"});
mongos> db.yql.insert({id:4,val:"this is a message on rac4:27020 --2011-11-02 9:52!"});
mongos> db.yql.insert({id:5,val:"this is a message on rac4:27020 --2011-11-02 9:53!"});
mongos> db.yql.insert({id:6,val:"this is a message on rac4:27020 --2011-11-02 9:55!"});
mongos> db.yql.insert({id:7,val:"this is a message on rac4:27020 --2011-11-02 9:56!"});
mongos> db.yql.insert({id:8,val:"this is a message on rac4:27020 --2011-11-02 9:56!"});
mongos> db.yql.insert({id:9,val:"this is a message on rac4:27020 --2011-11-02 9:57!"});
mongos> db.yql.insert({id:10,val:"this is a message on rac4:27020 --2011-11-02 9:58!"});
mongos> db.yql.insert({id:11,val:"this is a message on rac4:27020 --2011-11-02 9:59!"});
mongos> db.yql.insert({id:12,val:"this is a message on rac4:27020 --2011-11-02 10:00!"});
mongos> db.yql.insert({id:13,val:"this is a message on rac4:27020 --2011-11-02 10:01!"});
mongos> db.yql.insert({id:14,val:"this is a message on rac4:27020 --2011-11-02 10:02!"});
mongos> db.yql.insert({id:15,val:"this is a message on rac4:27020 --2011-11-02 10:03!"});
mongos> db.yql.insert({id:16,val:"this is a message on rac4:27020 --2011-11-02 10:04!"});
mongos> db.yql.find();
{ "_id" : ObjectId("4eb298b3adbd9673afee95e3"), "id" : 1, "val" : "this is a message on rac4 mongos !" }
{ "_id" : ObjectId("4eb2995badbd9673afee95e4"), "id" : 2, "val" : "this is a message on rac4:27020 --2011-11-02 9:47!" }
{ "_id" : ObjectId("4eb29962adbd9673afee95e5"), "id" : 2, "val" : "this is a message on rac4:27020 --2011-11-02 9:49!" }
{ "_id" : ObjectId("4eb29970adbd9673afee95e6"), "id" : 3, "val" : "this is a message on rac4:27020 --2011-11-02 9:50!" }
{ "_id" : ObjectId("4eb2997badbd9673afee95e7"), "id" : 4, "val" : "this is a message on rac4:27020 --2011-11-02 9:52!" }
{ "_id" : ObjectId("4eb29985adbd9673afee95e8"), "id" : 5, "val" : "this is a message on rac4:27020 --2011-11-02 9:53!" }
{ "_id" : ObjectId("4eb299eaadbd9673afee95e9"), "id" : 6, "val" : "this is a message on rac4:27020 --2011-11-02 9:55!" }
{ "_id" : ObjectId("4eb299f3adbd9673afee95ea"), "id" : 7, "val" : "this is a message on rac4:27020 --2011-11-02 9:56!" }
{ "_id" : ObjectId("4eb29a59adbd9673afee95eb"), "id" : 8, "val" : "this is a message on rac4:27020 --2011-11-02 9:56!" }
{ "_id" : ObjectId("4eb29a59adbd9673afee95ec"), "id" : 9, "val" : "this is a message on rac4:27020 --2011-11-02 9:57!" }
{ "_id" : ObjectId("4eb29a59adbd9673afee95ed"), "id" : 10, "val" : "this is a message on rac4:27020 --2011-11-02 9:58!" }
{ "_id" : ObjectId("4eb29a59adbd9673afee95ee"), "id" : 11, "val" : "this is a message on rac4:27020 --2011-11-02 9:59!" }
{ "_id" : ObjectId("4eb29a59adbd9673afee95ef"), "id" : 12, "val" : "this is a message on rac4:27020 --2011-11-02 10:00!" }
{ "_id" : ObjectId("4eb29a59adbd9673afee95f0"), "id" : 13, "val" : "this is a message on rac4:27020 --2011-11-02 10:01!" }
{ "_id" : ObjectId("4eb29a59adbd9673afee95f1"), "id" : 14, "val" : "this is a message on rac4:27020 --2011-11-02 10:02!" }
{ "_id" : ObjectId("4eb29a59adbd9673afee95f2"), "id" : 15, "val" : "this is a message on rac4:27020 --2011-11-02 10:03!" }
{ "_id" : ObjectId("4eb29a59adbd9673afee95f3"), "id" : 16, "val" : "this is a message on rac4:27020 --2011-11-02 10:04!" }
用 db..stats() 可以查看具体的 Shard 存储信息
mongos> db.yql.stats();
{
"sharded" : true,
"flags" : 1,
"ns" : "test.yql",
"count" : 17,
"numExtents" : 1,
"size" : 1616,
"storageSize" : 8192,
"totalIndexSize" : 8176,
"indexSizes" : {
"_id_" : 8176
},
"avgObjSize" : 95.05882352941177,
"nindexes" : 1,
"nchunks" : 1,
"shards" : {
"shard0000" : { --表示yql被拆分到了10.250.7.225这台机器上了
"ns" : "test.yql",
"count" : 17,
"size" : 1616,
"avgObjSize" : 95.05882352941177,
"storageSize" : 8192,
"numExtents" : 1,
"nindexes" : 1,
"lastExtentSize" : 8192,
"paddingFactor" : 1,
"flags" : 1,
"totalIndexSize" : 8176,
"indexSizes" : {
"_id_" : 8176
},
"ok" : 1
}
},
"ok" : 1
}
mongos>