MongoDB管理与开发精要《红丸出品》22.6 Sharding分片之管理维护

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22.6 管理维护Sharding

22.6.1列出所有的Shard Server

> db.runCommand({ listshards: 1 }) --列出所有的Shard Server { "shards" : [ { "_id" : "shard0000", "host" : "localhost:20000" }, { "_id" : "shard0001", "host" : "localhost:20001" } ], "ok" : 1 }

22.6.2查看Sharding信息

> printShardingStatus() --查看Sharding信息 --- Sharding Status --- sharding version: { "_id" : 1, "version" : 3 } shards: { "_id" : "shard0000", "host" : "localhost:20000" } { "_id" : "shard0001", "host" : "localhost:20001" } databases: { "_id" : "admin", "partitioned" : false, "primary" : "config" } { "_id" : "test", "partitioned" : true, "primary" : "shard0000" } test.users chunks: shard0000 1 { "_id" : { $minKey : 1 } } -->> { "_id" : { $maxKey : 1 } } on : shard0000 { "t" : 1000, "i" : 0 } >

22.6.3判断是否是Sharding

> db.runCommand({ isdbgrid:1 }) { "isdbgrid" : 1, "hostname" : "localhost", "ok" : 1 } >

22.6.4 对现有的表进行Sharding

刚才我们是对表test.users进行分片了，下面我们将对库中现有的未分片的表test.users_2进行分片处理

表最初状态如下，可以看出他没有被分片过：

> db.users_2.stats() { "ns" : "test.users_2", "sharded" : false, "primary" : "shard0000", "ns" : "test.users_2", "count" : 500000, "size" : 48000016, "avgObjSize" : 96.000032, "storageSize" : 61875968, "numExtents" : 11, "nindexes" : 1, "lastExtentSize" : 15001856, "paddingFactor" : 1, "flags" : 1, "totalIndexSize" : 20807680, "indexSizes" : { "_id_" : 20807680 }, "ok" : 1 }

对其进行分片处理:

> use admin switched to db admin > db.runCommand({ shardcollection: "test.users_2", key: { _id:1 }}) { "collectionsharded" : "test.users_2", "ok" : 1 }

再次查看分片后的表的状态，可以看到它已经被我们分片了

> use test switched to db test > db.users_2.stats() { "sharded" : true, "ns" : "test.users_2", "count" : 505462, …… "shards" : { "shard0000" : { "ns" : "test.users_2", …… "ok" : 1 }, "shard0001" : { "ns" : "test.users_2", …… "ok" : 1 } }, "ok" : 1 } >

22.6.5 新增ShardServer

刚才我们演示的是新增分片表，接下来我们演示如何新增Shard Server

启动一个新Shard Server进程

[root@localhost ~]# mkdir /data/shard/s2 [root@localhost ~]# /Apps/mongo/bin/mongod --shardsvr --port 20002 --dbpath /data/shard/s2 --fork --logpath /data/shard/log/s2.log --directoryperdb all output going to: /data/shard/log/s2.log forked process: 6772

配置新Shard Server

[root@localhost ~]# /Apps/mongo/bin/mongo admin --port 40000 MongoDB shell version: 1.8.1 connecting to: 127.0.0.1:40000/admin > db.runCommand({ addshard:"localhost:20002" }) { "shardAdded" : "shard0002", "ok" : 1 } > printShardingStatus() --- Sharding Status --- sharding version: { "_id" : 1, "version" : 3 } shards: { "_id" : "shard0000", "host" : "localhost:20000" } { "_id" : "shard0001", "host" : "localhost:20001" } { "_id" : "shard0002", "host" : "localhost:20002" } --新增Shard Server databases: { "_id" : "admin", "partitioned" : false, "primary" : "config" } { "_id" : "test", "partitioned" : true, "primary" : "shard0000" } test.users chunks: shard0002 2 shard0000 21 shard0001 21 too many chunksn to print, use verbose if you want to force print test.users_2 chunks: shard0001 46 shard0002 1 shard0000 45 too many chunksn to print, use verbose if you want to force print

查看分片表状态，以验证新Shard Server

> use test switched to db test > db.users_2.stats() { "sharded" : true, "ns" : "test.users_2", …… "shard0002" : { --新的Shard Server已有数据 "ns" : "test.users_2", "count" : 21848, "size" : 2097408, "avgObjSize" : 96, "storageSize" : 2793472, "numExtents" : 5, "nindexes" : 1, "lastExtentSize" : 2097152, "paddingFactor" : 1, "flags" : 1, "totalIndexSize" : 1277952, "indexSizes" : { "_id_" : 1277952 }, "ok" : 1 } }, "ok" : 1 } >

我们可以发现，当我们新增Shard Server后数据自动分布到了新Shard上，这是由MongoDB内部自已实现的。

22.6.6 移除Shard Server

有些时候有于硬件资源有限，所以我们不得不进行一些回收工作，下面我们就要将刚刚启用的Shard Server回收，系统首先会将在这个即将被移除的Shard Server上的数据先平均分配到其它的ShardServer上，然后最终在将这个Shard Server踢下线, 我们需要不停的调用db.runCommand({"removeshard": "localhost:20002"});来观察这个移除操作进行到哪里了：

> use admin switched to db admin > db.runCommand({"removeshard" : "localhost:20002"}); { "msg" : "draining started successfully", "state" : "started", "shard" : "shard0002", "ok" : 1 } > db.runCommand({"removeshard" : "localhost:20002"}); { "msg" : "draining ongoing", "state" : "ongoing", "remaining" : { "chunks" : NumberLong(44), "dbs" : NumberLong(0) }, "ok" : 1 } …… > db.runCommand({"removeshard" : "localhost:20002"}); { "msg" : "draining ongoing", "state" : "ongoing", "remaining" : { "chunks" : NumberLong(1), "dbs" : NumberLong(0) }, "ok" : 1 } > db.runCommand({"removeshard" : "localhost:20002"}); { "msg" : "removeshard completed successfully", "state" : "completed", "shard" : "shard0002", "ok" : 1 } > db.runCommand({"removeshard" : "localhost:20002"}); { "assertion" : "can't find shard for: localhost:20002", "assertionCode" : 13129, "errmsg" : "db assertion failure", "ok" : 0 }

最终移除后，当我们再次调用db.runCommand({"removeshard": "localhost:20002"});的时候系统会报错，已便通知我们不存在20002这个端口的Shard Server了，因为它已经被移除掉了。

接下来我们看一下表中的数据分布：

> use test switched to db test > db.users_2.stats() { "sharded" : true, "ns" : "test.users_2", "count" : 500000, "size" : 48000000, "avgObjSize" : 96, "storageSize" : 95203584, "nindexes" : 1, "nchunks" : 92, "shards" : { "shard0000" : { "ns" : "test.users_2", "count" : 248749, "size" : 23879904, "avgObjSize" : 96, "storageSize" : 61875968, "numExtents" : 11, "nindexes" : 1, "lastExtentSize" : 15001856, "paddingFactor" : 1, "flags" : 1, "totalIndexSize" : 13033472, "indexSizes" : { "_id_" : 13033472 }, "ok" : 1 }, "shard0001" : { "ns" : "test.users_2", "count" : 251251, "size" : 24120096, "avgObjSize" : 96, "storageSize" : 33327616, "numExtents" : 8, "nindexes" : 1, "lastExtentSize" : 12079360, "paddingFactor" : 1, "flags" : 1, "totalIndexSize" : 10469376, "indexSizes" : { "_id_" : 10469376 }, "ok" : 1 } }, "ok" : 1 }

可以看出数据又被平均分配到了另外2台Shard Server上了，对业务没什么特别大的影响。

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《MongoDB管理与开发精要》、《Redis实战》作者

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