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Configure Non-Voting Replica Set Member

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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, use the replSetReconfig command or its mongosh helper method rs.reconfig() to set its members[n].votes and members[n].priority values to 0. Non-voting replica set members must have a priority of 0.

Note

Starting in MongoDB 4.4, replica reconfiguration can add or remove no more than one voting replica set member at a time. To modify the votes of multiple members, issue a series of replSetReconfig or rs.reconfig() operations to modify one member at a time. See Reconfiguration Can Add or Remove No More than One Voting Member at a Time for more information.

The following procedure converts configures a single secondary replica set member to be non-voting. To convert the primary member to be non-voting, you must first successfully step the primary down using replSetStepDown or its shell helper rs.stepDown() before performing this procedure.

1) Connect to the Replica Set Primary

Connect mongosh to the replica set primary:

mongosh --host "<hostname>:<port>"

Replace the <hostname> and <port> with the hostname and port of the replica set primary. Include any other parameters required for your deployment.

2) Retrieve the Replica Configuration

Issue the rs.conf() method in the shell and assign the result to a variable cfg:

cfg = rs.conf();

The returned document contains a members array, where each element in the array contains the configuration for a single replica set member.

3) Configure the Member to be Non-Voting

For the replica member to change to be non-voting, set its votes and priority to 0.

cfg.members[n].votes = 0;
cfg.members[n].priority = 0;

Replace n with the array index position of the member to modify. The members array is zero-indexed, where the first element in the array has an index position of 0.

The array index position of a member in the members array is distinct from the members[n]._id of a specific member. Do not use the _id to reference the array index position of any any member in members.

4) Reconfigure the Replica Set with the New Configuration

Use rs.reconfig() method to reconfigure the replica set with the updated replica set configuration document.

rs.reconfig(cfg);
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.
  • Avoid reconfiguring replica sets that contain members of different MongoDB versions as validation rules may differ across MongoDB versions.
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