Ceph » CephFS

When major events happen like client eviction, we often want to get an idea what went wrong but production clusters usually run with low debugging (1/5) so it's difficult to diagnose what happened.

Make a config-enabled feature to dump recent events (see also MDSDaemon::respawn) during these events. Some interesting ones to start with:

- evicts a client.
- is in a recovery state for >60seconds.
- misses beacon ACKs from monitors
- misses internal heartbeats

The config option should be a float indicating the minimum time between these major events where the MDS will dump the in-memory logs. The default should probably be 60 seconds to limit log file bloat in a production environment. A <=0.0 value disables the feature.