I’m facing an issue with my MongoDB cluster since upgrading to version 6.0. Here’s my current setup:
1 primary
3 secondaries
1 arbiter
Since the upgrade, I’ve noticed that the arbiter is no longer being recognized properly. I get the following error message: "arbiters are not supported with quarterly rapid releases", even though I’m on an LTS version (6.0.17).
The problem becomes more apparent when I cut off two nodes (e.g., a primary and a secondary). In this case, the cluster stops functioning correctly and I see the message "rsm monitoring host in expedited mode until we detect a primary". This indicates that MongoDB is in expedited monitoring mode trying to detect a new primary.
It seems like the quorum needed to elect a new primary isn’t being met, which is causing the issue.
I’m not entirely sure what’s going wrong or how to resolve it. Do you have any suggestions or explanations for this behavior?
Since there wasn’t a reply to your message, I tried to run it by our documentation bot. Here is the response I got
When upgrading to MongoDB 6.0, it’s important to note that starting from MongoDB 5.3, support for multiple arbiters in a replica set is disabled by default. This change can affect quorum and recognition of arbiters in your replica set.
Key Points:
Single Arbiter Recommendation: Use a single arbiter to avoid data consistency issues. Multiple arbiters can prevent reliable use of the majority write concern, leading to potential data loss if a secondary node falls behind and the cluster is reconfigured.
Default Behavior: By default, MongoDB 5.3 and later versions do not allow multiple arbiters. If you attempt to add multiple arbiters, the server will return an error unless all nodes are started with the --setParameter 'allowMultipleArbiters=true' option.
Configuration: To add multiple arbiters, start each node with the allowMultipleArbiters parameter set to true:
mongod --setParameter allowMultipleArbiters=true
Example Error:
If you try to add multiple arbiters without the necessary parameter, you might encounter an error like:
MongoServerError: Multiple arbiters are not allowed unless all nodes were started with --setParameter 'allowMultipleArbiters=true'
Security Considerations:
Authentication: Arbiters exchange credentials with other set members to authenticate, and this process is encrypted.
Communication: Votes during elections, heartbeats, and configuration data exchanges are not encrypted unless your deployment uses TLS/SSL.
To ensure smooth operation and avoid quorum issues, adhere to the single arbiter recommendation and configure your replica set accordingly.
