The Fetcher Manager metrics group contains metrics regarding the stats of replica fetchers for consumers. The metrics available are:

• Failed fetcher thread count
• Failed partition error count
• Max Message fetch lag count
• Min message fetch rate per minute

Failed fetcher thread count

This metric shows the number of failed fetcher threads. The number increments when the replica manager’s thread encounters unexpected errors and shuts down.

Failed partition error count

This metric increments when: 

• Partition truncation fails
• Storage exception is encountered
• Partition has an older epoch than current leader
• Any other errors encountered during a fetch request.

Max Message fetch lag count

This metric shows the max fetched message lag count across all fetchers/topics/partitions.

Min message fetch rate per minute

This metric shows the minimum number of messages fetched in a rolling one minute window across all fetchers/topics/partitions.