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背景
當MongoDB存儲海量的數據時，一臺機器可能不足以存儲數據，也可能不足以提供可接受的讀寫吞吐量。這時，我們就可以通過在多臺機器上分割數據，使得數據庫系統能存儲和處理更多的數據。
1、MongoDB sharding簡介
三種角色：
配置服務器(config)：是一個獨立的mongod進程，保存集群和分片的元數據，即各分片包含了哪些數據的信息。
路由服務器(mongos)：起到一個路由的功能，供程序連接。本身不保存數據，在啟動時從配置服務器加載集群信息.
分片服務器(sharding)：是一個獨立mongod進程，保存數據信息。可以是一臺服務器，如果想要高可用也可以配置成副本集。
2、實驗環境
兩臺機器的IP:
172.16.101.54 sht-sgmhadoopcm-01
172.16.101.55 sht-sgmhadoopnn-01
config server:
172.16.101.55:27017
mongos:
172.16.101.55:27018
sharding:
172.16.101.54:27017
172.16.101.54:27018
172.16.101.54:27019
2、啟動config服務
修改配置服務器的配置文件，主要是參數clusterRole指定角色為configsvr
[root@sht-sgmhadoopnn-01 mongodb]# cat /etc/mongod27017.conf systemLog: destination: file path: "/usr/local/mongodb/log/mongod27017.log" logAppend: true storage: dbPath: /usr/local/mongodb/data/db27017 journal: enabled: true processManagement: fork: true pidFilePath: /usr/local/mongodb/data/db27017/mongod27017.pid net: port: 27017 bindIp: 0.0.0.0 setParameter: enableLocalhostAuthBypass: false sharding: clusterRole: configsvr archiveMovedChunks: true
[root@sht-sgmhadoopnn-01 mongodb]# bin/mongod --config /etc/mongod27017.conf
warning: bind_ip of 0.0.0.0 is unnecessary; listens on all ips by default
about to fork child process, waiting until server is ready for connections.
forked process: 31033
child process started successfully, parent exiting
3、啟動mongos服務
修改路由服務器的配置文件，主要是參數configDB指定config服務器的IP和port，不需要配置有關數據文件的信息，因為路由服務器不存儲數據
[root@sht-sgmhadoopnn-01 mongodb]# cat /etc/mongod27018.conf systemLog: destination: file path: "/usr/local/mongodb/log/mongod27018.log" logAppend: true processManagement: fork: true pidFilePath: /usr/local/mongodb/data/db27018/mongod27018.pid net: port: 27018 bindIp: 0.0.0.0 setParameter: enableLocalhostAuthBypass: false sharding: autoSplit: true configDB: 172.16.101.55:27017 chunkSize: 64
[root@sht-sgmhadoopnn-01 mongodb]# bin/mongos --config /etc/mongod27018.conf
warning: bind_ip of 0.0.0.0 is unnecessary; listens on all ips by default
2018-11-10T18:57:13.705+0800 W SHARDING 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: 31167
child process started successfully, parent exiting
4、啟動sharding服務
就是一個普通的mongodb進程，普通的配置文件
[root@sht-sgmhadoopcm-01 mongodb]# cat /etc/mongod27017.conf systemLog: destination: file path: "/usr/local/mongodb/log/mongod27017.log" logAppend: true storage: dbPath: /usr/local/mongodb/data/db27017 journal: enabled: true processManagement: fork: true pidFilePath: /usr/local/mongodb/data/db27017/mongod27017.pid net: port: 27017 bindIp: 0.0.0.0 setParameter: enableLocalhostAuthBypass: false
[root@sht-sgmhadoopcm-01 mongodb]# bin/mongod --config /etc/mongod27017.conf
[root@sht-sgmhadoopcm-01 mongodb]# bin/mongod --config /etc/mongod27018.conf
[root@sht-sgmhadoopcm-01 mongodb]# bin/mongod --config /etc/mongod27019.conf
5、登陸mongos服務并添加sharding信息
[root@sht-sgmhadoopnn-01 mongodb]# bin/mongo --port=27018
mongos> sh.addShard("172.16.101.54:27017")
{ "shardAdded" : "shard0000", "ok" : 1 }
mongos> sh.addShard("172.16.101.54:27018")
{ "shardAdded" : "shard0001", "ok" : 1 }
mongos> sh.addShard("172.16.101.54:27019")
{ "shardAdded" : "shard0002", "ok" : 1 }
查看集群分片信息
mongos> sh.status()
--- Sharding Status ---
sharding version: {
"_id" : 1,
"minCompatibleVersion" : 5,
"currentVersion" : 6,
"clusterId" : ObjectId("5be6b98a507b3e0370eb36b4")
}
shards:
{ "_id" : "shard0000", "host" : "172.16.101.54:27017" }
{ "_id" : "shard0001", "host" : "172.16.101.54:27018" }
{ "_id" : "shard0002", "host" : "172.16.101.54:27019" }
balancer:
Currently enabled: yes
Currently running: no
Failed balancer rounds in last 5 attempts: 0
Migration Results for the last 24 hours:
No recent migrations
databases:
{ "_id" : "admin", "partitioned" : false, "primary" : "config" }mongos> db.runCommand({listshards:1})
{
"shards" : [
{
"_id" : "shard0000",
"host" : "172.16.101.54:27017"
},
{
"_id" : "shard0001",
"host" : "172.16.101.54:27018"
},
{
"_id" : "shard0002",
"host" : "172.16.101.54:27019"
}
],
"ok" : 1
}6、開啟分片
需要執行分片的庫和集合，以及分片模式，分片模式分為兩種hash和range
[root@sht-sgmhadoopnn-01 mongodb]# bin/mongo --port=27018
分片庫是testdb
mongos> sh.enableSharding("testdb")
{ "ok" : 1 }
(1)hash分片模式測試
分片的集合是collection1，根據id進行hash分片
mongos> sh.shardCollection("testdb.collection1",{"_id":"hashed"})
{ "collectionsharded" : "testdb.collection1", "ok" : 1 }
共插入10個測試document
mongos> use testdb
switched to db testdb
mongos> for(var i=0;i<10;i++){db.collection1.insert({name:"jack"+i});}
WriteResult({ "nInserted" : 1 })
mongos> sh.status()
--- Sharding Status ---
sharding version: {
"_id" : 1,
"minCompatibleVersion" : 5,
"currentVersion" : 6,
"clusterId" : ObjectId("5be6b98a507b3e0370eb36b4")
}
shards:
{ "_id" : "shard0000", "host" : "172.16.101.54:27017" }
{ "_id" : "shard0001", "host" : "172.16.101.54:27018" }
{ "_id" : "shard0002", "host" : "172.16.101.54:27019" }
balancer:
Currently enabled: yes
Currently running: no
Failed balancer rounds in last 5 attempts: 0
Migration Results for the last 24 hours:
2 : Success
databases:
{ "_id" : "admin", "partitioned" : false, "primary" : "config" }
{ "_id" : "test", "partitioned" : false, "primary" : "shard0000" }
{ "_id" : "testdb", "partitioned" : true, "primary" : "shard0000" }
testdb.collection1
shard key: { "_id" : "hashed" }
chunks:
shard0000 2
shard0001 2
shard0002 2
{ "_id" : { "$minKey" : 1 } } -->> { "_id" : NumberLong("-6148914691236517204") } on : shard0000 Timestamp(3, 2)
{ "_id" : NumberLong("-6148914691236517204") } -->> { "_id" : NumberLong("-3074457345618258602") } on : shard0000 Timestamp(3, 3)
{ "_id" : NumberLong("-3074457345618258602") } -->> { "_id" : NumberLong(0) } on : shard0001 Timestamp(3, 4)
{ "_id" : NumberLong(0) } -->> { "_id" : NumberLong("3074457345618258602") } on : shard0001 Timestamp(3, 5)
{ "_id" : NumberLong("3074457345618258602") } -->> { "_id" : NumberLong("6148914691236517204") } on : shard0002 Timestamp(3, 6)
{ "_id" : NumberLong("6148914691236517204") } -->> { "_id" : { "$maxKey" : 1 } } on : shard0002 Timestamp(3, 7)查看每個sharding上的數據分布情況db.collection.stats()
mongos> db.collection1.stats()
{
"sharded" : true,
"paddingFactorNote" : "paddingFactor is unused and unmaintained in 3.0. It remains hard coded to 1.0 for compatibility only.",
"userFlags" : 1,
"capped" : false,
"ns" : "testdb.collection1",
"count" : 10, #共十個document數據
"numExtents" : 3,
"size" : 480,
"storageSize" : 24576,
"totalIndexSize" : 49056,
"indexSizes" : {
"_id_" : 24528,
"_id_hashed" : 24528
},
"avgObjSize" : 48,
"nindexes" : 2,
"nchunks" : 6,
"shards" : {
"shard0000" : {
"ns" : "testdb.collection1",
"count" : 0,
"size" : 0,
"numExtents" : 1,
"storageSize" : 8192,
"lastExtentSize" : 8192,
"paddingFactor" : 1,
"paddingFactorNote" : "paddingFactor is unused and unmaintained in 3.0. It remains hard coded to 1.0 for compatibility only.",
"userFlags" : 1,
"capped" : false,
"nindexes" : 2,
"totalIndexSize" : 16352,
"indexSizes" : {
"_id_" : 8176,
"_id_hashed" : 8176
},
"ok" : 1
},
"shard0001" : {
"ns" : "testdb.collection1",
"count" : 6,
"size" : 288,
"avgObjSize" : 48,
"numExtents" : 1,
"storageSize" : 8192,
"lastExtentSize" : 8192,
"paddingFactor" : 1,
"paddingFactorNote" : "paddingFactor is unused and unmaintained in 3.0. It remains hard coded to 1.0 for compatibility only.",
"userFlags" : 1,
"capped" : false,
"nindexes" : 2,
"totalIndexSize" : 16352,
"indexSizes" : {
"_id_" : 8176,
"_id_hashed" : 8176
},
"ok" : 1
},
"shard0002" : {
"ns" : "testdb.collection1",
"count" : 4,
"size" : 192,
"avgObjSize" : 48,
"numExtents" : 1,
"storageSize" : 8192,
"lastExtentSize" : 8192,
"paddingFactor" : 1,
"paddingFactorNote" : "paddingFactor is unused and unmaintained in 3.0. It remains hard coded to 1.0 for compatibility only.",
"userFlags" : 1,
"capped" : false,
"nindexes" : 2,
"totalIndexSize" : 16352,
"indexSizes" : {
"_id_" : 8176,
"_id_hashed" : 8176
},
"ok" : 1
}
},
"ok" : 1
}分別登陸sharding節點查看數據分布,和通過命令db.collection.stats()看到的結果一致
可以發現節點27017上沒有數據，節點27018上有6個document，節點27019上有4個document，出現這種情況的原因可能是插入的數據量太小，沒有分布均勻，數據量越大，分布越均勻。
[root@sht-sgmhadoopcm-01 mongodb]# bin/mongo 172.16.101.54:27017/testdb
> db.collection1.find()
[root@sht-sgmhadoopcm-01 mongodb]# bin/mongo 172.16.101.54:27018/testdb
> db.collection1.find()
{ "_id" : ObjectId("5be6c467e6467cc8077da816"), "name" : "jack1" }
{ "_id" : ObjectId("5be6c467e6467cc8077da817"), "name" : "jack2" }
{ "_id" : ObjectId("5be6c467e6467cc8077da818"), "name" : "jack3" }
{ "_id" : ObjectId("5be6c467e6467cc8077da81a"), "name" : "jack5" }
{ "_id" : ObjectId("5be6c467e6467cc8077da81c"), "name" : "jack7" }
{ "_id" : ObjectId("5be6c467e6467cc8077da81e"), "name" : "jack9" }
[root@sht-sgmhadoopcm-01 mongodb]# bin/mongo 172.16.101.54:27019/testdb
> db.collection1.find()
{ "_id" : ObjectId("5be6c467e6467cc8077da815"), "name" : "jack0" }
{ "_id" : ObjectId("5be6c467e6467cc8077da819"), "name" : "jack4" }
{ "_id" : ObjectId("5be6c467e6467cc8077da81b"), "name" : "jack6" }
{ "_id" : ObjectId("5be6c467e6467cc8077da81d"), "name" : "jack8" }
(2)range分片模式測試
分片的集合是collection2，根據name進行range分片
mongos> sh.shardCollection("testdb.collection2",{"name":1})
{ "collectionsharded" : "testdb.collection2", "ok" : 1 }
mongos> for(var i=0;i<1000;i++){db.collection2.insert({name:"jack"+i});}
WriteResult({ "nInserted" : 1 })
mongos> sh.status()
--- Sharding Status ---
sharding version: {
"_id" : 1,
"minCompatibleVersion" : 5,
"currentVersion" : 6,
"clusterId" : ObjectId("5be6b98a507b3e0370eb36b4")
}
shards:
{ "_id" : "shard0000", "host" : "172.16.101.54:27017" }
{ "_id" : "shard0001", "host" : "172.16.101.54:27018" }
{ "_id" : "shard0002", "host" : "172.16.101.54:27019" }
balancer:
Currently enabled: yes
Currently running: no
Failed balancer rounds in last 5 attempts: 0
Migration Results for the last 24 hours:
4 : Success
databases:
{ "_id" : "admin", "partitioned" : false, "primary" : "config" }
{ "_id" : "test", "partitioned" : false, "primary" : "shard0000" }
{ "_id" : "testdb", "partitioned" : true, "primary" : "shard0000" }
testdb.collection1
shard key: { "_id" : "hashed" }
chunks:
shard0000 2
shard0001 2
shard0002 2
{ "_id" : { "$minKey" : 1 } } -->> { "_id" : NumberLong("-6148914691236517204") } on : shard0000 Timestamp(3, 2)
{ "_id" : NumberLong("-6148914691236517204") } -->> { "_id" : NumberLong("-3074457345618258602") } on : shard0000 Timestamp(3, 3)
{ "_id" : NumberLong("-3074457345618258602") } -->> { "_id" : NumberLong(0) } on : shard0001 Timestamp(3, 4)
{ "_id" : NumberLong(0) } -->> { "_id" : NumberLong("3074457345618258602") } on : shard0001 Timestamp(3, 5)
{ "_id" : NumberLong("3074457345618258602") } -->> { "_id" : NumberLong("6148914691236517204") } on : shard0002 Timestamp(3, 6)
{ "_id" : NumberLong("6148914691236517204") } -->> { "_id" : { "$maxKey" : 1 } } on : shard0002 Timestamp(3, 7)
testdb.collection2
shard key: { "name" : 1 }
chunks:
shard0000 1
shard0001 1
shard0002 1
{ "name" : { "$minKey" : 1 } } -->> { "name" : "jack1" } on : shard0001 Timestamp(2, 0)
{ "name" : "jack1" } -->> { "name" : "jack5" } on : shard0002 Timestamp(3, 0)
{ "name" : "jack5" } -->> { "name" : { "$maxKey" : 1 } } on : shard0000 Timestamp(3, 1)mongos> db.collection2.stats()
{
"sharded" : true,
"paddingFactorNote" : "paddingFactor is unused and unmaintained in 3.0. It remains hard coded to 1.0 for compatibility only.",
"userFlags" : 1,
"capped" : false,
"ns" : "testdb.collection2",
"count" : 1000,
"numExtents" : 6,
"size" : 48032,
"storageSize" : 221184,
"totalIndexSize" : 130816,
"indexSizes" : {
"_id_" : 65408,
"name_1" : 65408
},
"avgObjSize" : 48.032,
"nindexes" : 2,
"nchunks" : 3,
"shards" : {
"shard0000" : {
"ns" : "testdb.collection2",
"count" : 555,
"size" : 26656,
"avgObjSize" : 48,
"numExtents" : 3,
"storageSize" : 172032,
"lastExtentSize" : 131072,
"paddingFactor" : 1,
"paddingFactorNote" : "paddingFactor is unused and unmaintained in 3.0. It remains hard coded to 1.0 for compatibility only.",
"userFlags" : 1,
"capped" : false,
"nindexes" : 2,
"totalIndexSize" : 65408,
"indexSizes" : {
"_id_" : 32704,
"name_1" : 32704
},
"ok" : 1
},
"shard0001" : {
"ns" : "testdb.collection2",
"count" : 1,
"size" : 48,
"avgObjSize" : 48,
"numExtents" : 1,
"storageSize" : 8192,
"lastExtentSize" : 8192,
"paddingFactor" : 1,
"paddingFactorNote" : "paddingFactor is unused and unmaintained in 3.0. It remains hard coded to 1.0 for compatibility only.",
"userFlags" : 1,
"capped" : false,
"nindexes" : 2,
"totalIndexSize" : 16352,
"indexSizes" : {
"_id_" : 8176,
"name_1" : 8176
},
"ok" : 1
},
"shard0002" : {
"ns" : "testdb.collection2",
"count" : 444,
"size" : 21328,
"avgObjSize" : 48,
"numExtents" : 2,
"storageSize" : 40960,
"lastExtentSize" : 32768,
"paddingFactor" : 1,
"paddingFactorNote" : "paddingFactor is unused and unmaintained in 3.0. It remains hard coded to 1.0 for compatibility only.",
"userFlags" : 1,
"capped" : false,
"nindexes" : 2,
"totalIndexSize" : 49056,
"indexSizes" : {
"_id_" : 24528,
"name_1" : 24528
},
"ok" : 1
}
},
"ok" : 1
}參考鏈接
Sharding
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