fsync

Forces the mongod process to flush all pending writes from the storage layer to disk. Optionally, you can use fsync to lock the mongod instance and block write operations for the purpose of capturing backups.

As applications write data, MongoDB records the data in the storage layer and then writes the data to disk within the syncPeriodSecs interval, which is 60 seconds by default. Run fsync when you want to flush writes to disk ahead of that interval.

The fsync command has the following syntax:

{ fsync: 1, async: <Boolean>, lock: <Boolean> }

The fsync command has the following fields:

Field	Type	Description
`fsync`	integer	Enter “1” to apply `fsync`.
`async`	boolean	Optional. Runs `fsync` asynchronously. By default, the `fsync` operation is synchronous.
`lock`	boolean	Optional. Locks `mongod` instance and blocks all write operations.

Examples

Run Asynchronously

The fsync operation is synchronous by default. To run fsync asynchronously, use the async field set totrue:

{ fsync: 1, async: true }

The operation returns immediately. To view the status of the fsync operation, check the output ofdb.currentOp().

Lock `mongod` Instance

NOTE

Changed in version 3.2: fsync command with the lock option can ensure that the data files do not change for MongoDB instances using either the MMAPv1 or the WiredTiger storage engines, thus providing consistency for the purposes of creating backups.

In previous MongoDB versions, fsync command with the lock option cannot guarantee a consistent set of files for low-level backups (e.g. via file copy cp, scp, tar) for WiredTiger.

The primary use of fsync is to lock the mongod instance in order to back up the files within mongod‘sdbPath. The operation flushes all data to the storage layer and blocks all write operations until you unlock themongod instance.

To lock the database, use the lock field set to true:

{ fsync: 1, lock: true }

You may continue to perform read operations on a mongod instance that has a fsync lock. However, after the first write operation all subsequent read operations wait until you unlock the mongod instance.

Unlock `mongod` Instance

To unlock the mongod, use db.fsyncUnlock():

db.fsyncUnlock();

巴特西

mongodb给我们提供了fsync+lock机制把数据暴力的刷到硬盘上

fsync

Examples

Run Asynchronously

Lock `mongod` Instance

Unlock `mongod` Instance

见：https://docs.mongodb.com/manual/reference/command/fsync/

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巴特西

mongodb给我们提供了fsync+lock机制把数据暴力的刷到硬盘上

fsync

Examples

Run Asynchronously

Lock mongod Instance

Unlock mongod Instance

见：https://docs.mongodb.com/manual/reference/command/fsync/

最新文章

热门文章

Lock `mongod` Instance

Unlock `mongod` Instance