OPTIONS

Configure Non-Voting Replica Set Member

Non-voting members allow you to add additional members for read distribution beyond the maximum seven voting members. To configure a member as non-voting, set its votes value to 0.

Example

To disable the ability to vote in elections for the fourth, fifth, and sixth replica set members, use the following command sequence in the mongo shell connected to the primary. You identify each replica set member by its array index in the members array:

cfg = rs.conf()
cfg.members[3].votes = 0
cfg.members[4].votes = 0
cfg.members[5].votes = 0
rs.reconfig(cfg)

This sequence gives 0 votes to the fourth, fifth, and sixth members of the set according to the order of the members array in the output of rs.conf(). This setting allows the set to elect these members as primary but does not allow them to vote in elections. Place voting members so that your designated primary or primaries can reach a majority of votes in the event of a network partition.

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 _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, the mongod closes all client connections. While this typically takes 10-20 seconds, try to make these changes during scheduled maintenance periods.
  • To successfully reconfigure a replica set, a majority of the members must be accessible. If your replica set has an even number of members, add an arbiter to ensure that members can quickly obtain a majority of votes in an election for primary.

In general and when possible, all members should have only 1 vote. This prevents intermittent ties, deadlocks, or the wrong members from becoming primary. Use priority to control which members are more likely to become primary.