Error
Error Code:
155
MongoDB Error 155: Oplog Application on Primary
Description
This error indicates that a MongoDB instance, currently acting as the primary member of a replica set, attempted to apply operations from the oplog. This is an unexpected state because the primary's role is to generate and propagate oplog entries, not to apply them as a secondary would. It typically points to an internal state inconsistency or a misdirected administrative action.
Error Message
Cannot Apply Oplog While Primary
Known Causes
3 known causesReplica Set State Inconsistency
The internal state of the replica set may have become corrupted or inconsistent, causing the primary node to incorrectly attempt to apply oplog entries.
Misdirected Replication Commands
An administrative action or automated script might have issued a replication command intended for a secondary member directly to the primary.
Unexpected Primary Role Transition
During complex primary election or failover scenarios, a newly elected primary might briefly enter an inconsistent state related to oplog application.
Solutions
Coming SoonDetailed step-by-step solutions for this error are being prepared. In the meantime, try these general troubleshooting tips:
General Troubleshooting Tips
- Check the error message carefully for specific details
- Review recent changes that might have caused the error
- Search for the exact error code in the official documentation
- Check log files for additional context
- Try restarting the application or service