Configure a Delayed Replica Set Member
The length of the secondary
members[n].slaveDelay must fit within the window of the oplog. If the oplog is shorter than the
members[n].slaveDelay window, the delayed member cannot successfully replicate operations.
The following example sets a 1-hour delay on a secondary member currently at the index
0 in the
members array. To set the delay, issue the following sequence of operations in a
mongo shell connected to the primary:
After the replica set reconfigures, the delayed secondary member cannot become primary and is hidden from applications. The
members[n].slaveDelay value delays both replication and the member’s oplog by 3600 seconds (1 hour).
When updating the replica configuration object, access the replica set members in the
members array with the array index. The array index begins with
0. Do not confuse this index value with the value of the
members[n]._id field in each document in the
rs.reconfig()shell method can force the current primary to step down, which causes an election. When the primary steps down, the
mongodcloses all client connections. While this typically takes 10-20 seconds, try to make these changes during scheduled maintenance periods.
- Avoid reconfiguring replica sets that contain members of different MongoDB versions as validation rules may differ across MongoDB versions.