replSetStepDown

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Description描述

replSetStepDown

Instructs the primary of the replica set to become a secondary. After the primary steps down, eligible secondaries will hold an election for primary.

The command does not immediately step down the primary. If no electable secondaries are up to date with the primary, the primary waits up to secondaryCatchUpPeriodSecs (by default 10 seconds) for a secondary to catch up. Once an electable secondary is available, the command steps down the primary.

Once stepped down, the original primary becomes a secondary and is ineligible from becoming primary again for the remainder of time specified by replSetStepDown: <seconds>.

For a detailed explanation of the command ‘s execution, see Behavior.

Note

The command is only valid against the primary and throws an error if run on a non-primary member.

The replSetStepDown can only run on the admin database and has the following prototype form:

db.adminCommand( {
    replSetStepDown: <seconds>,
    secondaryCatchUpPeriodSecs: <seconds>,
    force: <true|false>
} )

replSetStepDown takes the following fields as arguments:

Field字段Type类型Description描述
replSetStepDown number

The number of seconds to step down the primary, during which time the stepdown member is ineligible for becoming primary. If you specify a non-numeric value, the command uses 60 seconds.

The stepdown period starts from the time that the mongod receives the command. The stepdown period must be greater than the secondaryCatchUpPeriodSecs.

secondaryCatchUpPeriodSecs number

Optional.可选。The number of seconds that the mongod will wait for an electable secondary to catch up to the primary.

When specified, secondaryCatchUpPeriodSecs overrides the default wait time of either 10 seconds or if force: true, 0 seconds.

force boolean

Optional.可选。A boolean that determines whether the primary steps down if no electable and up-to-date secondary exists within the wait period.

If true, the primary steps down even if no suitable secondary member exists; this could lead to rollbacks if a secondary with replication lag becomes the new primary.

If false, the primary does not step down if no suitable secondary member exists and the command returns an error.

Defaults to false.

Behavior行为

Concurrent Operations

The replSetStepDown command attempts to terminate long running user operations that block the primary from stepping down, such as an index build, a write operation or a map-reduce job.

Availability of Eligible Secondaries

The command then initiates a catchup period where it waits up to secondaryCatchUpPeriodSeconds, by default 10 seconds, for a secondary to become up-to-date with the primary. The primary only steps down if a secondary is up-to-date with the primary during the catchup period to prevent rollbacks.

If no electable secondary meets this criterion by the end of the waiting period, the primary does not step down and the command errors. You can override this behavior and issue with command with the force: true option to immediately step down the primary.

Once the primary steps down successfully, that node cannot become the primary for the remainder of the replSetStepDown: <seconds> period, which began when the node received the command.

Client Connections

Starting in MongoDB 4.2, replSetStepDown command no longer closes all client connections.

In MongoDB 4.0 and earlier, replSetStepDown command closes all client connections during the step down. Because the disconnect includes the connection used to run the command, you cannot retrieve the return status of the command if the command completes successfully. You can only retrieve the return status of the command if it errors. When running the 4.0 and earlier command in a script, the script should account for this behavior.

Writes During Stepdown

Note

All writes to the primary fail during the period starting when the replSetStepDown command is received until either a new primary is elected, or if there are no electable secondaries, the original primary resumes normal operation.

Writes that were in progress when replSetStepDown is run are killed. In-progress transactions also fail with "TransientTransactionError" and can be retried as a whole.

The time period where writes fail is at maximum:

secondaryCatchUpPeriodSecs (10s by default) + electionTimeoutMillis (10s by default).

Election Handoff

Changed in version 4.0.2:If the parameter enableElectionHandoff is true (default), when a primary steps down from rs.stepDown() (or the replSetStepDown command without the force: true), the stepped-down primary nominates an eligible secondary to call an election immediately. Otherwise, secondaries can wait up to settings.electionTimeoutMillis before calling an election. The stepped down primary does not wait for the effects of the handoff. For more information, see enableElectionHandoff.

Examples示例

Step Down with Default Options

The following example, run on the current primary, attempts to step down the member for 120 seconds.

The operation waits up to the default 10 seconds for a secondary to catch up. If no suitable secondary exists, the primary does not step down and the command errors.

Note

All writes to the primary fail during the period starting when the replSetStepDown command is received until either a new primary is elected, or if there are no electable secondaries, the original primary resumes normal operation.

Writes that were in progress when replSetStepDown is run are killed. In-progress transactions also fail with "TransientTransactionError" and can be retried as a whole.

The time period where writes fail is at maximum:

secondaryCatchUpPeriodSecs (10s by default) + electionTimeoutMillis (10s by default).

db.adminCommand( { replSetStepDown: 120 } )

Specify Wait Time for Secondary Catch Up

The following example, run on the current primary, attempts to step down the member for 120 seconds, waiting up to 15 seconds for an electable secondary to catch up. If no suitable secondary exists, the primary does not step down and the command errors.

Note

All writes to the primary fail during the period starting when the replSetStepDown command is received until either a new primary is elected, or if there are no electable secondaries, the original primary resumes normal operation.

Writes that were in progress when replSetStepDown is run are killed. In-progress transactions also fail with "TransientTransactionError" and can be retried as a whole.

The time period where writes fail is at maximum:

secondaryCatchUpPeriodSecs (10s by default) + electionTimeoutMillis (10s by default).

db.adminCommand( { replSetStepDown: 120, secondaryCatchUpPeriodSecs: 15 } )

Specify Secondary Catch Up with Force Step Down

The following example, run on the current primary, attempts to step down the member for 120 seconds, waiting up to 15 seconds for an electable secondary to catch up. Because of the force: true option, the primary steps down even if no suitable secondary exists.

Note

All writes to the primary fail during the period starting when the replSetStepDown command is received until either a new primary is elected, or if there are no electable secondaries, the original primary resumes normal operation.

Writes that were in progress when replSetStepDown is run are killed. In-progress transactions also fail with "TransientTransactionError" and can be retried as a whole.

The time period where writes fail is at maximum:

secondaryCatchUpPeriodSecs (10s by default) + electionTimeoutMillis (10s by default).

db.adminCommand( { replSetStepDown: 120, secondaryCatchUpPeriodSecs: 15, force: true } )

See also参阅

rs.stepDown()