Configure a Delayed Replica Set Member
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To configure a delayed secondary member, set its
members[n].priority value to 0, its
members[n].hidden value to true, and
its members[n].slaveDelay value to the
number of seconds to delay.
Important
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.
When you configure a delayed member, the delay applies both to replication and to the member's oplog. For details on delayed members and their uses, see Delayed Replica Set Members.
Example
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:
cfg = rs.conf() cfg.members[0].priority = 0 cfg.members[0].hidden = true cfg.members[0].slaveDelay = 3600 rs.reconfig(cfg)
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 members array.
Warning
The
rs.reconfig()shell method can force the current primary to step down, which causes an election. When the primary steps down, themongodcloses 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.