Fix Lost Primary
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At time T, no primary was detected in replica set ABC.
Alert Conditions
You can configure alert conditions in the project-level alert settings page to trigger alerts.
To learn more about the alert condition, see Replica set has no primary.
Common Triggers
A network partition is preventing all members of the replica set from communicating with each other.
There are not enough voting members in the replica set to keep a primary. A simple majority is required to have a primary. This can happen if too many hosts are down (or not responding) to replica set heartbeats.
There is not an electable member when the primary goes down.
Fix the Immediate Problem
Ensure a majority of votes are available in the replica set. If hosts have been shut down permanently, ensure they are removed from the replica set configuration.
Use basic ping tests from one host to another to ensure they can communicate with each other.
Implement a Long-Term Solution
Make sure there is more than one data-bearing member with a priority greater than 0.
To learn more, see Replica Set Elections in the MongoDB manual.
Monitor Your Progress
View the following charts to monitor whether the deployment is exhausting resources:
Normalized System CPU
Monitor CPU usage to determine whether data is retrieved from disk instead of memory.
Disk IOPs
Monitor whether disk IOPS approaches the maximum provisioned IOPS. Determine whether the deployment can handle future workloads.
Connections
Monitor connections to determine whether the current connection limits are sufficient
To learn more, see View Deployment Metrics.