rs.syncFrom()

  • rs.syncFrom()
  • Provides a wrapper around the replSetSyncFrom, whichallows administrators to temporarily override the default synctarget for the current member. Specify the name of the member youwant to replicate from in the form of [hostname]:[port].

Changed in version 3.2: MongoDB 3.2 replica set members with 1 vote cannot sync from members with 0 votes.

Behavior

Sync Logic

Changed in version 3.4.

If an initial sync operation is in progress when you runreplSetSyncFrom, replSetSyncFrom stops the in-progress initial sync andrestarts the sync process with the new target. In previous versions,if you run replSetSyncFrom during initial sync, MongoDB produces noerror messages, but the sync target will not change until after theinitial sync operation.

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

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, andmust be able to answer data queries.
  • Be accessible.
  • Be a member of the same set in the replica set configuration.
  • Build indexes with themembers[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 secondsbehind the current member, mongod will log a warning but willstill replicate from the lagging member. See alsoReplication Lag and Flow Control.

Persistence

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

  • The mongod instance restarts.
  • The connection between the mongod and the sync targetcloses.
  • If the sync target falls more than 30 seconds behind anothermember of the replica set.

Example

To use the rs.syncFrom() helper in the mongo shell:

  1. rs.syncFrom("myHost:27017");

See also

replSetSyncFrom.