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setUserWriteBlockMode (database command)

Definition

setUserWriteBlockMode

New in version 6.0.

The setUserWriteBlockMode command blocks and unblocks writes to the entire cluster.

During cluster-to-cluster sync, mongosync, the cluster-to-cluster synchronization tool, uses the setUserWriteBlockMode command to block writes on the destination cluster. For more information, see the HTTP API start command.

If you already blocked writes on a replica set, subsequent calls to setUserWriteBlockMode with global: true fail with an IllegalOperation error if the specified reason does not match the reason you provided when you initially enabled write-blocking. The error message includes both the current reason and the reason specified in the failed command. Sharded clusters do not enforce this constraint.

Note

Users and applications with the bypassWriteBlockingMode privilege can bypass the block and continue to perform writes.

Compatibility

This command is available in deployments hosted in the following environments:

MongoDB Atlas: The fully managed service for MongoDB deployments in the cloud

Important

This command is not supported in M0 and Flex clusters. For more information, see Unsupported Commands.

MongoDB Enterprise: The subscription-based, self-managed version of MongoDB
MongoDB Community: The source-available, free-to-use, and self-managed version of MongoDB

Syntax

The command has the following syntax:

db.adminCommand(
   {
     setUserWriteBlockMode: 1,
     global: <boolean>,
     reason: <string>  // Optional
   }
)

Command Fields

The command takes the following fields:

Field	Type	Description
`setUserWriteBlockMode`	integer	Set this field to `1`.
`global`	boolean	Blocks writes on a cluster when set to `true`. To enable writes on a cluster, set `global: false`.
`reason`	string	Optional. Specifies the reason for blocking writes. Accepts the following values: `"Unspecified"` - Default when you do not provide any reason. `"ClusterToClusterMigrationInProgress"` - Indicates blocked writes due to ongoing cluster-to-cluster migration. `"DiskUseThresholdExceeded"` - Indicates blocked writes because disk usage has exceeded a threshold.

Required Access

To execute the setUserWriteBlockMode command, the user must have the setUserWriteBlockMode privilege.

Example

Enable user write block mode:
```
db.adminCommand( {
   setUserWriteBlockMode: 1,
   global: true
} )
```
Add a record to the collection:
```
db.names.insertOne( { name: "George Washington Cable" } )
```
The server blocks the write because the user write block is enabled.
Example Output:
```
MongoServerError: User writes blocked
```
Disable user write block mode:
```
db.adminCommand( {
   setUserWriteBlockMode: 1,
   global: false
} )
```
Add a record to the collection:
```
db.names.insertOne( { name: "George Washington Cable" } )
```
The insertOne() method writes to a collection. The server allows the write because the user write block is disabled.

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