rs.syncFrom()

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Behavior

Example

rs.syncFrom()

Temporarily overrides the default sync target for the current member.

Important

mongosh Method

This page documents a mongosh method. This is not the documentation for database commands or language-specific drivers, such as Node.js.

For the database command, see the replSetFreeze command.

For MongoDB API drivers, refer to the language-specific MongoDB driver documentation.

Specify the name of the member you want to replicate from in the form of [hostname]:[port].

Behavior

Sync Logic

If an initial sync operation is in progress when you run replSetSyncFrom, replSetSyncFrom stops the in-progress initial sync and restarts the sync process with the new target.

Only modify the default sync logic as needed, and always exercise caution.

Target

The member to sync from must be a valid source for data in the set. To sync from a member, the member must:

Have data. It cannot be an arbiter, in startup or recovering mode, and must be able to answer data queries.
Be accessible.
Be a member of the same set in the replica set configuration.
Build indexes with the members[n].buildIndexes setting.
A different member of the set, to prevent syncing from itself.

If you attempt to replicate from a member that is more than 10 seconds behind the current member, mongod will log a warning but will still replicate from the lagging member. See also Replication Lag and Flow Control.

Persistence

replSetSyncFrom provide a temporary override of default behavior. mongod will revert to the default sync behavior in the following situations:

The mongod instance restarts.
The connection between the mongod and the sync target closes.
If the sync target falls more than 30 seconds behind another member of the replica set.

Example

To use the rs.syncFrom() helper in mongosh:

rs.syncFrom("myHost:27017");