Reconfigure a Replica Set with Unavailable Members
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This document provides steps for re-configuring a replica set when only a minority of members are accessible.
You may need to use the procedure, for example, in a geographically distributed replica set, where no local group of members can reach a majority. See Replica Set Elections for more information on this situation.
force option forces a new configuration onto the member. Use this procedure only to recover from catastrophic interruptions. Do not use
force every time you reconfigure. Also, do not use the
force option in any automatic scripts and do not use
force when there is still a primary.
To force reconfiguration:
Back up a surviving member.
Connect to a surviving member and save the current configuration. Consider the following example commands for saving the configuration:
On the same member, remove the down and unreachable members of the replica set from the
membersarray by setting the array equal to the surviving members alone. Consider the following example, which uses the
cfgvariable created in the previous step:
On the same member, reconfigure the set by using the
rs.reconfig()command with the
forceoption set to
This operation forces the secondary to use the new configuration. The configuration is then propagated to all the surviving members listed in the
membersarray. The replica set then elects a new primary.
When you use
force : true, the version number in the replica set configuration increases significantly, by tens or hundreds of thousands. This is normal and designed to prevent set version collisions if you accidentally force re-configurations on both sides of a network partition and then the network partitioning ends.
If the failure or partition was only temporary, shut down or decommission the removed members as soon as possible.