[feature request] Keep track of last successful post to subscribed instances

[mhamzahkhan]

Hello!

I apologise if this is already present. I was thinking it would be useful to store the timestamp of when a relay last accepted a relayed message.

I couldn't find any way to do this from the data stored in Redis, but I might have missed something.

This would be very useful to clean up dead instances that didn't unsubscribe prior to shutting down.

[thystra]

FYI from a downstream maintainer: this is implemented in
thystra/Activity-Relay.

Stable v2.5.0 stores durable per-receiver:

• last successful delivery time;
• last failed delivery time;
• total successful and failed deliveries; and
• consecutive failure count.

Current receiver health is exposed through privacy-filtered
/status.json schema version 4 and Prometheus metrics.

We are deliberately separating observation from deletion. A stale-receiver
retention and cleanup policy is planned with configuration switches, dry-run
reporting, active-member protection, and a hard prohibition on deleting health
state while queued or claimed work still references the receiver.

Release details:
https://github.com/thystra/Activity-Relay/releases/tag/v2.5.0