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The collections in the config database support:config数据库中的集合支持：

Restrictions限制

Starting in MongoDB 5.0, non-transaction reads are not allowed on the config.transactions collection with the following read concerns and options:从MongoDB 5.0开始，config.transactions集合上不允许进行非事务读取，并有以下读取问题和选项：

Important

The schema of the config database is internal and may change between releases of MongoDB. config数据库的模式是内部的，可能会在MongoDB的不同版本之间发生变化。The config database is not a dependable API, and users should not write data to the config database in the course of normal operation or maintenance.config数据库不是一个可靠的API，用户在正常运行或维护过程中不应将数据写入config数据库。

Note

You cannot perform read/write operations to the collections in the config database inside a multi-document transaction.不能在多文档事务中对config数据库中的集合执行读/写操作。

Collections to Support Sharded Cluster Operations支持共享群集操作的集合

To access the config database and view the list of collections that support sharding operations, connect mongosh to a mongos instance in a sharded cluster and issue the following:要访问config数据库并查看支持分片操作的集合列表，请将mongosh连接到分片集群中的mongos实例，并发出以下命令：

use config

show collections
Note

If running with access control, ensure you have privileges that grant listCollections action on the database.如果使用访问控制运行，请确保您具有对数据库授予listCollections操作的权限。

The config database is mainly for internal use, and during normal operations you should never manually insert or store data in it. 配置数据库主要用于内部使用，在正常操作过程中，您不应该手动在其中插入或存储数据。However, if you need to verify the write availability of the config server for a sharded cluster, you can insert a document into a test collection (after making sure that no collection of that name already exists):但是，如果您需要验证配置服务器对分片集群的写入可用性，则可以将文档插入测试集合（在确保不存在该名称的集合之后）：

Warning

Modification of the config database on a functioning system may lead to instability or inconsistent data sets. 在正常运行的系统上修改config数据库可能会导致不稳定或数据集不一致。If you must modify the config database, use mongodump to create a full backup of the config database.如果必须修改config数据库，请使用mongodump创建config数据库的完整备份。

db.testConfigServerWriteAvail.insertOne( { a : 1 } )

If the operation succeeds, the config server is available to process writes.如果操作成功，则配置服务器可用于处理写入。

Future releases of the server may include different collections in the config database, so be careful when selecting a name for your test collection.服务器的未来版本可能会在配置数据库中包含不同的集合，因此在为测试集合选择名称时要小心。

MongoDB uses the following collections in the config database to support sharding:MongoDB在config数据库中使用以下集合来支持分片：

config.changelog
Tip

Internal MongoDB Metadata内部MongoDB元数据

The config database is internal: applications and administrators should not modify or depend upon its content in the course of normal operation.config数据库是内部的：应用程序和管理员在正常操作过程中不应修改或依赖其内容。

The changelog collection stores a document for each change to the metadata of a sharded collection.changelog集合为分片集合的元数据的每次更改存储一个文档。

Example

The following example displays a single record of a chunk split from a changelog collection:以下示例显示了从changelog集合中分割的区块的单个记录：

{
 "_id" : "<hostname>-<timestamp>-<increment>",
 "server" : "<hostname><:port>",
 "clientAddr" : "127.0.0.1:63381",
 "time" : ISODate("2012-12-11T14:09:21.039Z"),
 "what" : "split",
 "ns" : "<database>.<collection>",
 "details" : {
    "before" : {
       "min" : {
          "<database>" : { $minKey : 1 }
       },
       "max" : {
          "<database>" : { $maxKey : 1 }
       },
       "lastmod" : Timestamp(1000, 0),
       "lastmodEpoch" : ObjectId("000000000000000000000000")
    },
    "left" : {
       "min" : {
          "<database>" : { $minKey : 1 }
       },
       "max" : {
          "<database>" : "<value>"
       },
       "lastmod" : Timestamp(1000, 1),
       "lastmodEpoch" : ObjectId(<...>)
    },
    "right" : {
       "min" : {
          "<database>" : "<value>"
       },
       "max" : {
          "<database>" : { $maxKey : 1 }
       },
       "lastmod" : Timestamp(1000, 2),
       "lastmodEpoch" : ObjectId("<...>")
    },
    "owningShard" : "<value>"
 }
}

Each document in the changelog collection contains the following fields:changelog集合中的每个文档都包含以下字段：

config.changelog._id

The value of changelog._id is: <hostname>-<timestamp>-<increment>.changelog的值_id为：<hostname>-<timestamp>-<increment>。

config.changelog.server

The hostname of the server that holds this data.保存此数据的服务器的主机名。

config.changelog.clientAddr

A string that holds the address of the client, a mongos instance that initiates this change.保存客户端地址的字符串，该客户端是发起此更改的mongos实例。

config.changelog.time

A ISODate timestamp that reflects when the change occurred.反映更改发生时间的ISODate时间戳。

config.changelog.what

Reflects the type of change recorded. Possible values include:反映记录的更改类型。可能的值包括：

  • dropCollection
  • dropCollection.start
  • dropDatabase
  • dropDatabase.start
  • moveChunk.start
  • moveChunk.commit
  • split
  • multi-split
config.changelog.ns

Namespace where the change occurred.发生更改的命名空间。

config.changelog.details

A document that contains additional details regarding the change. 包含有关更改的其他详细信息的文档。The structure of the details document depends on the type of change.details文档的结构取决于更改的类型。

config.chunks
Tip

Internal MongoDB Metadata内部MongoDB元数据

The config database is internal: applications and administrators should not modify or depend upon its content in the course of normal operation.config数据库是内部的：应用程序和管理员在正常操作过程中不应修改或依赖其内容。

The chunks collection stores a document for each chunk in the cluster. chunks集合为集群中的每个块存储一个文档。Consider the following example of a document for a chunk named mydb.foo-a_\"cat\":考虑以下名为mydb.foo-a_\"cat\"的区块的文档示例：

{
   "_id" : "mydb.foo-a_\"cat\"",
   "lastmod" : Timestamp(2, 1),
   "uuid": "c025d039-e626-435e-b2d2-c1d436038041",
   "min" : {
         "animal" : "cat"
   },
   "max" : {
         "animal" : "dog"
   },
   "shard" : "shard0004",
   "history" : [ { "validAfter" : Timestamp(1569368571, 27), "shard" : "shard0004" } ]
}

These documents store the range of values for the shard key that describe the chunk in the min and max fields. 这些文档将描述区块的分片键的值范围存储在min和max字段中。Additionally the shard field identifies the shard in the cluster that "owns" the chunk.此外，shard字段标识集群中“拥有”区块的分片。

config.collections
Tip

Internal MongoDB Metadata内部MongoDB元数据

The config database is internal: applications and administrators should not modify or depend upon its content in the course of normal operation.config数据库是内部的：应用程序和管理员在正常操作过程中不应修改或依赖其内容。

The collections collection stores a document for each sharded collection in the cluster. collections集合为集群中的每个分片集合存储一个文档。Given a collection named pets in the records database, a document in the collections collection would resemble the following:给定records数据库中名为pets的集合，collections集合中的文档将类似于以下内容：

{
   "_id" : "records.pets",
   "lastmod" : ISODate("2021-07-21T15:48:15.193Z"),
   "timestamp": Timestamp(1626882495, 1),
   "key" : {
         "a" : 1
   },
   "unique" : false,
   "lastmodEpoch" : ObjectId("5078407bd58b175c5c225fdc"),
   "uuid" :  UUID("f8669e52-5c1b-4ea2-bbdc-a00189b341da")
}
config.databases
Tip

Internal MongoDB Metadata内部MongoDB元数据

The config database is internal: applications and administrators should not modify or depend upon its content in the course of normal operation.config数据库是内部的：应用程序和管理员在正常操作过程中不应修改或依赖其内容。

The databases collection stores a document for each database in the cluster.databases集合为集群中的每个数据库存储一个文档。

For each database, the corresponding document displays the name, the database's primary shard , the database's sharding enabled status, and a version.对于每个数据库，相应的文档显示名称、数据库的主分片、数据库的分片启用状态和版本。

{ "_id" : "test", "primary" : "shardA", "partitioned" : true, "version" : { "uuid" : UUID("516a5f79-5eb9-4844-8ee9-b8e9de91b760"), "timestamp" : Timestamp(1626894204, 1), "lastMod" : 1 } }
{ "_id" : "hr", "primary" : "shardA", "partitioned" : false, "version" : { "uuid" : UUID("8e39d61d-6259-4c33-a5ed-bcd2ae317b6f"), "timestamp" : Timestamp(1626895015, 1), "lastMod" : 1 } }
{ "_id" : "reporting", "primary" : "shardB", "partitioned" : false, "version" : { "uuid" : UUID("07c63242-51b3-460c-865f-a67b3372d792"), "timestamp" : Timestamp(1626895826, 1), "lastMod" : 1 } }

The method sh.status() returns this information in the Databases section.方法sh.status()在数据库部分中返回此信息。

config.lockpings
Tip

Internal MongoDB Metadata内部MongoDB元数据

The config database is internal: applications and administrators should not modify or depend upon its content in the course of normal operation.config数据库是内部的：应用程序和管理员在正常操作过程中不应修改或依赖其内容。

The lockpings collection keeps track of the active components in the sharded cluster. lockpings集合跟踪已分片集群中的活动组件。Given a cluster with a mongos running on example.com:30000, the document in the lockpings collection would resemble:给定一个在example.com:30000上运行mongos的集群，lockpings集合中的文档将类似于：

{ "_id" : "example.com:30000:1350047994:16807", "ping" : ISODate("2012-10-12T18:32:54.892Z") }
config.locks
Tip

Internal MongoDB Metadata内部MongoDB元数据

The config database is internal: applications and administrators should not modify or depend upon its content in the course of normal operation.config数据库是内部的：应用程序和管理员在正常操作过程中不应修改或依赖其内容。

The locks collection stores the distributed locks. locks集合存储分布式锁。The primary of the config server replica set takes a lock by inserting a document into the locks collection.配置服务器副本集的主副本通过将文档插入locks集合来获取锁。

{
   "_id" : "test.myShardedCollection",
   "state" : 2,
   "process" : "ConfigServer",
   "ts" : ObjectId("5be0b9ede46e4f441a60d891"),
   "when" : ISODate("2018-11-05T21:52:00.846Z"),
   "who" : "ConfigServer:Balancer",
   "why" : "Migrating chunk(s) in collection test.myShardedCollection"
}

As of version 3.4, the state field will always have a value 2 to prevent any legacy mongos instances from performing the balancing operation. 从3.4版本起，state字段的值将始终为2，以防止任何遗留的mongos实例执行平衡操作。The when field specifies the time when the config server member became the primary.when字段指定配置服务器成员成为主要成员的时间。

In version 3.4, when the balancer is active, the balancer takes a lock, as in the following 3.4 example:在版本3.4中，当平衡器处于活动状态时，平衡器会锁定，如以下3.4示例所示：

{
   "_id" : "balancer",
   "state" : 2,
   "ts" : ObjectId("5be0bc6cb20effa83b15baa8"),
   "who" : "ConfigServer:Balancer",
   "process" : "ConfigServer",
   "when" : ISODate("2018-11-05T21:56:13.096Z"),
   "why" : "CSRS Balancer"
}

Starting in version 3.6, the balancer no longer takes a "lock". 从3.6版开始，平衡器不再具有“锁定”功能。If you have upgraded from 3.4 to 3.6, you may choose to delete any residual "_id" : "balancer" documents.如果您已从3.4升级到3.6，则可以选择删除任何剩余的"_id" : "balancer"文档。

config.migrationCoordinators

New in version 4.4. 4.4版新增。

The migrationCoordinators collection exists on each shard and stores a document for each in-progress chunk migration from this shard to another shard. migrationCoordinators集合存在于每个分片上，并为从该分片到另一个分片的每个正在进行的块迁移存储一个文档。The chunk migration fails if the document cannot be written to a majority of the members of the shard's replica set.如果文档无法写入到分片副本集的大多数成员，则块迁移失败。

When a migration is complete, the document describing the migration is deleted from the collection.迁移完成后，将从集合中删除描述迁移的文档。

config.mongos
Tip

Internal MongoDB Metadata内部MongoDB元数据

The config database is internal: applications and administrators should not modify or depend upon its content in the course of normal operation.config数据库是内部的：应用程序和管理员在正常操作过程中不应修改或依赖其内容。

The mongos collection stores a document for each mongos instance affiliated with the cluster. The cluster maintains this collection for reporting purposes.mongos集合为与集群关联的每个mongos实例存储一个文档。集群维护此集合以用于报告目的。

Each document in the mongos collection contains these fields:mongos集合中的每个文档都包含以下字段：

Field字段Data Type数据类型Description描述
_idStringThe hostname and port where the mongos is running. mongos运行的主机名和端口。The _id is formatted as <hostname>:<port>._id的格式为<hostname>:<port>。
advisoryHostFQDNsArray of stringsArray of the mongos's fully qualified domain names (FQDNs).mongos的完全限定域名（FQDN）数组。
createdDateWhen the mongos was started. 当mongos启动时。
New in version 5.2. 5.2版新增。
mongoVersionStringVersion of MongoDB that the mongos is running.mongos正在运行的MongoDB版本。
pingDatemongos instances send pings to the config server every 30 seconds. mongos实例每30秒向config服务器发送一次ping。This field indicates the last ping time.此字段指示最后一次ping时间。
upNumberLongNumber of seconds the mongos has been up as of the last ping.截至上次ping，mongos已上升的秒数。
waitingBooleanAs of MongoDB 3.4, this field is always true and is only present for backward compatibility.从MongoDB 3.4开始，该字段始终为true，并且仅用于向后兼容性。

The following document shows the status of the mongos running on example.com:27017.以下文档显示了运行在example.com:27017上的mongos的状态。

[
   {
     _id: 'example.com:27017',
     advisoryHostFQDNs: [ "example.com" ],
     created: ISODate("2021-11-22T16:32:13.708Z"),
     mongoVersion: "5.2.0",
     ping: ISODate("2021-12-15T22:09:23.161Z"),
     up: Long("2007429"),
     waiting: true
   }
]
config.rangeDeletions

The rangeDeletions collection exists on each shard and stores a document for each chunk range that contains orphaned documents. rangeDeletions集合存在于每个分片上，并为包含孤立文档的每个区块范围存储一个文档。The chunk migration fails if the document cannot be written to a majority of the members of the shard's replica set.如果文档无法写入到分片副本集的大多数成员，则块迁移失败。

When the orphaned chunk range is cleaned up, the document describing the range is deleted from the collection.清理孤立区块范围时，将从集合中删除描述该范围的文档。

config.settings
Tip

Internal MongoDB Metadata内部MongoDB元数据

The config database is internal: applications and administrators should not modify or depend upon its content in the course of normal operation.config数据库是内部的：应用程序和管理员在正常操作过程中不应修改或依赖其内容。

The settings collection holds the following sharding configuration settings:settings集合包含以下分片配置设置：

  • Range size. 范围大小。To change range size, see Modify Range Size in a Sharded Cluster. 要更改范围大小，请参阅修改分片群集中的范围大小。The specified chunksize value is in megabytes.指定的chunksize值以兆字节为单位。
  • Balancer settings. 平衡器设置。To change the balancer settings, including balancer status, see Manage Sharded Cluster Balancer.要更改平衡器设置，包括平衡器状态，请参阅管理共享群集平衡器。
  • Autosplit:自动拆分：

    Starting in MongoDB 6.1, automatic chunk splitting is not performed. 从MongoDB 6.1开始，不执行自动区块分割。This is because of balancing policy improvements. Auto-splitting commands still exist, but do not perform an operation. 这是因为平衡政策的改进。自动拆分命令仍然存在，但不执行操作。For details, see Balancing Policy Changes.有关详细信息，请参阅平衡策略更改。

    In MongoDB versions earlier than 6.1:在6.1之前的MongoDB版本中：

Example documents in the settings collection:settings集合中的示例文档：

{ "_id" : "chunksize", "value" : 64 }
{ "_id" : "balancer", "mode" : "full", "stopped" : false }
config.shards
Tip

Internal MongoDB Metadata内部MongoDB元数据

The config database is internal: applications and administrators should not modify or depend upon its content in the course of normal operation.config数据库是内部的：应用程序和管理员在正常操作过程中不应修改或依赖其内容。

The shards collection represents each shard in the cluster in a separate document, as in the following:shardss集合在一个单独的文档中表示集群中的每个分片，如下所示：

{ "_id" : "shard0000", "host" : "localhost:30000", "state" : 1 }

If the shard is a replica set, the host field displays the name of the replica set, then a slash, then a comma-separated list of the hostnames of each member of the replica set, as in the following example:如果分片是副本集，那么host字段将显示副本集的名称，然后是斜杠，然后是副本集每个成员的主机名的逗号分隔列表，如下例所示：

{ "_id" : "shard0001", "host" : "shard0001/localhost:27018,localhost:27019,localhost:27020", "state" : 1 }

If the shard has zones assigned, this document has a tags field, that holds an array of the zones to which it is assigned, as in the following example:如果分片分配了区域，则此文档有一个tags字段，该字段包含一个分配给它的区域数组，如以下示例所示：

{ "_id" : "shard0002", "host" : "localhost:30002", "state" : 1, "tags": [ "NYC" ] }
config.tags
Tip

Internal MongoDB Metadata内部MongoDB元数据

The config database is internal: applications and administrators should not modify or depend upon its content in the course of normal operation.config数据库是内部的：应用程序和管理员在正常操作过程中不应修改或依赖其内容。

The tags collection holds documents for each zone range in the cluster. tags集合保存集群中每个区域范围的文档。The documents in the tags collection resemble the following:tags集合中的文档如下所示：

{
    "_id" : { "ns" : "records.users", "min" : { "zipcode" : "10001" } },
    "ns" : "records.users",
    "min" : { "zipcode" : "10001" },
    "max" : { "zipcode" : "10281" },
    "tag" : "NYC"
}
config.version
Tip

Internal MongoDB Metadata内部MongoDB元数据

The config database is internal: applications and administrators should not modify or depend upon its content in the course of normal operation.config数据库是内部的：应用程序和管理员在正常操作过程中不应修改或依赖其内容。

The version collection holds the current metadata version number. version集合包含当前元数据版本号。This collection contains only one document. 此集合仅包含一个文档。For example:例如：

{ "_id" : 1, "minCompatibleVersion" : 5, "currentVersion" : 6, "clusterId" : ObjectId("5d8bc01a690d8abbd2014ddd") }

To access the version collection, you must use the db.getCollection() method. 若要访问version集合，必须使用db.getCollection()方法。For example, to retrieve the collection's document:例如，要检索集合的文档：

db.getCollection("version").find()

Collections to Support Sessions支持会话的集合

Starting in MongoDB 3.6, the config database contains the internal collections to support causally consistent sessions for standalones, replica sets, and sharded clusters and retryable writes and transactions for replica sets and sharded clusters.从MongoDB 3.6开始，config数据库包含内部集合，以支持单机、副本集和分片集群的因果一致会话，以及副本集和分区集群的可重试写入和事务。

Warning

Do not manually modify or drop these collections.不要手动修改或删除这些集合。

To access these collections for a mongod or mongos instance, connect mongosh to the instance.要访问mongod或mongos实例的这些集合，请将mongosh连接到该实例。

config.system.sessions

The system.sessions collection stores session records that are available to all members of the deployment.system.sessions集合存储可供部署的所有成员使用的会话记录。

When a user creates a session on a mongod or mongos instance, the record of the session initially exists only in-memory on the instance. 当用户在mongod或mongos实例上创建会话时，会话的记录最初只存在于实例的内存中。Periodically, the instance will sync its cached sessions to the system.sessions collection; at which time, they are visible to all members of the deployment.实例将定期将其缓存的会话同步到system.sessions集合；此时，部署的所有成员都可以看到它们。

To view records in the system.sessions collection, use $listSessions.要查看system.sessions集合中的记录，请使用$listSessions。

Warning

Do not manually modify or drop the system.sessions collection.请勿手动修改或删除system.sessions集合。

In a sharded cluster, the system.sessions collection is sharded.在分片集群中，system.sessions集合是分片的。

  • When adding a shard to the sharded cluster, if the shard to add already contains its own system.sessions collection, MongoDB drops the new shard's system.sessions collection during the add process.当将一个分片添加到分片集群时，如果要添加的分片已经包含自己的system.sessions集合，MongoDB会在添加过程中丢弃新分片的system.sessions集合。
  • Starting in version 4.4 (and 4.2.7), MongoDB automatically splits the system.sessions collection into at least 1024 chunks and distributes the chunks uniformly across shards in the cluster.从版本4.4（和4.2.7）开始，MongoDB会自动将system.sessions集合拆分为至少1024个块，并将这些块均匀地分布在集群中的分片中。
config.transactions

The transactions collection stores records used to support retryable writes and transactions for replica sets and sharded clusters.transactions集合存储用于支持副本集和分片集群的可重试写入和事务的记录。

Warning

Do not manually modify or drop the transactions collection.请勿手动修改或删除transactions记录集合。