removeShard (database command数据库命令)

Definition定义

removeShard

Removes a shard from a sharded cluster. When you run removeShard, MongoDB drains the shard by using the balancer to move the shard's chunks to other shards in the cluster.从分片集群中删除分片。当你运行removeShard时，MongoDB会使用平衡器将分片的块移动到集群中的其他分片，从而耗尽分片。

If the shard has unsharded collections, you must drain all the unsharded collections from the shard. Starting in MongoDB 8.0, you can use sh.moveCollection() to move unsharded collections. 如果分片有未分片的集合，则必须从分片中清除所有未分片集合。从MongoDB 8.0开始，您可以使用sh.moveCollection()来移动未记录的集合。For details on the procedure to drain a shard, see Remove Shards from a Sharded Cluster.有关清空分片的过程的详细信息，请参阅从分片集群中删除分片。

Once the shard is drained, MongoDB removes the shard from the cluster.一旦分片被清空，MongoDB就会从集群中删除该分片。

Note

If you want to re-add a removed shard to your sharded cluster, you must clear the storage.dbPath of all the nodes of the shard to remove the shard's files of before you can re-add it.如果你想将一个已删除的分片重新添加到分片集群中，你必须清除分片所有节点的storage.dbPath以删除分片的文件，然后才能重新添加它。

Compatibility兼容性

This command is available in deployments hosted in the following environments:此命令在以下环境中托管的部署中可用：

• MongoDB Enterprise: The subscription-based, self-managed version of MongoDB：MongoDB的基于订阅的自我管理版本
• MongoDB Community: The source-available, free-to-use, and self-managed version of MongoDB：MongoDB的源代码可用、免费使用和自我管理版本

Syntax语法

The command has the following syntax:该命令具有以下语法：

db.adminCommand(
   {
     removeShard : <shardToRemove>
   }
)

Behavior行为

Example示例

From mongosh, the removeShard operation resembles the following:从mongosh来看，removeShard操作类似于以下内容：

db.adminCommand( { removeShard : "bristol01" } )

Replace bristol01 with the name of the shard to remove. When you run removeShard, the command returns with a message that resembles the following:将bristol01替换为要删除的分片的名称。当您运行removeShard时，该命令将返回一条类似于以下内容的消息：

{
   "msg" : "draining started successfully",
   "state" : "started",
   "shard" : "bristol01",
   "note" : "you need to call moveCollection for collectionsToMove and afterwards movePrimary for the dbsToMove",
   "dbsToMove" : [
      "fizz",
      "buzz"
   ],
   "collectionsToMove" : [
      "fizz.coll1",
      "buzz.coll1"
   ],
   "ok" : 1,
   "operationTime" : Timestamp(1575398919, 2),
   "$clusterTime" : {
      "clusterTime" : Timestamp(1575398919, 2),
      "signature" : {
         "hash" : BinData(0,"Oi68poWCFCA7b9kyhIcg+TzaGiA="),
         "keyId" : Long("6766255701040824328")
      }
   }
}

The balancer begins migrating ("draining") chunks from the shard named bristol01 to other shards in the cluster. These migrations happen slowly in order to avoid placing undue load on the cluster.平衡器开始将块从名为bristol01的分片迁移（“耗尽”）到集群中的其他分片。这些迁移过程缓慢，以避免给集群带来过重的负载。

If you run the command again, removeShard returns the current status of the process. 如果再次运行该命令，removeShard将返回进程的当前状态。For example, if the operation is in an ongoing state, the command returns an output that resembles the following:例如，如果操作处于ongoing状态，则该命令返回类似于以下内容的输出：

{
   "msg" : "draining ongoing",
   "state" : "ongoing",
   "remaining" : {
      "chunks" : Long(2),
      "dbs" : Long(2),
      "jumboChunks" : Long(0),
      "collectionsToMove": Long(2)
   },
   "note" : "you need to call moveCollection for collectionsToMove and afterwards movePrimary for the dbsToMove",
   "dbsToMove" : [
      "fizz",
      "buzz"
   ],
   "collectionsToMove" : [
      "fizz.coll1",
      "buzz.coll1"
   ],
   "ok" : 1,
   "operationTime" : Timestamp(1575399086, 1655),
   "$clusterTime" : {
      "clusterTime" : Timestamp(1575399086, 1655),
      "signature" : {
         "hash" : BinData(0,"XBrTmjMMe82fUtVLRm13GBVtRE8="),
         "keyId" : Long("6766255701040824328")
      }
   }
}

In the output, the remaining field includes the following fields:在输出中，remaining字段包括以下字段：

Continue checking the status of the removeShard command (i.e. rerun the command) until the number of chunks remaining is 0.继续检查removeShard命令的状态（即重新运行该命令），直到剩余的块数为0。

{
   "msg" : "draining ongoing",
   "state" : "ongoing",
   "remaining" : {
      "chunks" : Long(0),             // All chunks have moved
      "dbs" : Long(2),
      "jumboChunks" : Long(0),
      "collectionsToMove": Long(2)
   },
   "note" : "you need to call moveCollection for collectionsToMove and afterwards movePrimary for the dbsToMove",
   "dbsToMove" : [
      "fizz",
      "buzz"
   ],
   "collectionsToMove" : [
      "fizz.coll1",
      "buzz.coll1"
   ],
   "ok" : 1,
   "operationTime" : Timestamp(1575400343, 1),
   "$clusterTime" : {
      "clusterTime" : Timestamp(1575400343, 1),
      "signature" : {
         "hash" : BinData(0,"9plu5B/hw4uWAgEmjjBP3syw1Zk="),
         "keyId" : Long("6766255701040824328")
      }
   }
}

After the balancer drains all chunks from the shard, you may need to manually move your collections and databases out of the drained shard.在平衡器从分片中耗尽所有块后，您可能需要手动将集合和数据库移出耗尽的分片。

If the removeShard output contains collections in the collectionsToMove field, use moveCollection to move those collections to a shard other than the draining shard or drop the collections (which deletes the associated data files).如果removeShard输出在collectionsToMove字段中包含集合，请使用moveCollection将这些集合移动到排水分片以外的分片，或删除这些集合（这将删除关联的数据文件）。

If the removeShard output contains databases in the dbsToMove field, use movePrimary for those databases or drop the databases (which deletes the associated data files).如果removeShard输出在dbsToMove字段中包含数据库，请对这些数据库使用movePrimary或删除数据库（这将删除关联的数据文件）。

After the balancer completes moving all chunks off the shard and you have handled the dbsToMove and collectionsToMove, removeShard can finish. Running removeShard again returns output that resembles the following:在平衡器完成将所有块从分片中移出，并且您已经处理了dbsToMove和collectionsToMove之后，removeShard就可以完成了。再次运行removeShard将返回类似于以下内容的输出：

{
   "msg" : "removeshard completed successfully",
   "state" : "completed",
   "shard" : "bristol01",
   "ok" : 1,
   "operationTime" : Timestamp(1575400370, 2),
   "$clusterTime" : {
      "clusterTime" : Timestamp(1575400370, 2),
      "signature" : {
         "hash" : BinData(0,"JjSRciHECXDBXo0e5nJv9mdRG8M="),
         "keyId" : Long("6766255701040824328")
      }
   }
}