prometheus / prometheus/alertmanager
Split retention in 2 parts or multiple nflogs
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Description
We have a default of 120h retention.
While this default seems fine for the silences, it seems a lot too high for the nflog. Indeed, the nflog should ideally be kept only for ~110% of x=max( group_wait, group_interval, repeat_interval). When having a large number of alerts and a low x, alertmanager un-necessarily uses a lot of memory, because the state is broadcasted perpetually.
Here a heap of such a case: https://share.polarsignals.com/73d955e/
I see multiple ways forward:
- Multiple nflogs, with exponential durations (e.g. 1m, 1h, 12h, 10h), based on the duration the notification should stay available in the log.
- Allow setting a nflog-specific data retention policy.
Contributor guide
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First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by tracing the Alertmanager nflog retention and state-broadcast behavior described in the issue, using the linked heap report as context. Compare the proposed multiple-nflog and nflog-specific retention approaches; done means one agreed retention design is implemented and its memory behavior is validated.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- go
- Domain
- observability
- Issue type
- Feature
- Difficulty
- 5/5
- Estimated time
- Over a week
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 30/100