History Retention: Keep n last entries regardless of age

[oxzi]

This is a forwarded feature request that I have reworded.

The retention policy should be based on both a time duration and a minimum number of entries. In other words, all events older than the specified time duration should be deleted, except for the last n events, even if they are older than the specified time duration.

The motivation behind the proposal is to always keep the most recent events to understand the history of this host or service.

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CC: @bobapple, @lippserd

[julianbrost]

except for the last n events

Global n or per host/service n?

Global would mean there could still be hosts/services without any history, per host/service would make the history cleanup a per host/service operation (which probably requires major changes to the implementation and could very well make it more expensive).

[tranzatsource]

A global parameter to keep last n events is what we are expecting

[sol1-matt]

The motivation behind the proposal is to always keep the most recent events to understand the history of this host or service.

If this is the goal than I'd think you'd want to have a setting that is something like minimum-history: 2 per host or host/service combination so each would have at least 2 history entries minimum

setting a value like minimum-history: 500 and treating that as a minimum total would mean that a single host or service with a lot of activity would result low activity hosts or services losing their history (because keeping a minimum of 500 history events in total means the most active hosts and services win)