Currently, we have a bunch of GC TTL configuration settings:

• gcdaemon.ttl.conduit-logs
• gcdaemon.ttl.daemon-logs
• gcdaemon.ttl.differential-parse-cache
• gcdaemon.ttl.general-cache
• gcdaemon.ttl.herald-transcripts
• gcdaemon.ttl.markup-cache
• gcdaemon.ttl.task-archive

These settings are rarely useful and pretty cluttery for new installs.

We actually have significantly more garbage collectors than this (about 20), but most of them don't even have TTL settings.

Having these settings is useful to some degree. I've heard of at least two reasonable use cases from installs that want to control TTLs for garbage collection:

• One install has an information retention policy which requires purging the user activity logs after X days.
• Another install wants to retain build logs for a very long time (perhaps indefinitely) so they can serve as a component of a long-lasting audit record.

I'd like to make these TTL settings part of PhabricatorGarbageCollector, merge them all into one dictionary, shove that dictionary out of the way, and probably put a CLI interface on it. Something like this:

$ ./bin/garbage status
| Collector  | TTL      |
|------------|----------|
| User Logs  | 180 days |
| Build Logs | 60 days  |
| ...        | ...      |

$ ./bin/garbage set-ttl user-logs --days 45
Changed TTL of user logs from 180 days to 45 days.
This change will take effect the next time the daemons are restarted.

$ ./bin/garbage set-ttl build-logs --never
Changed TTL of build logs from 60 days to indefinite retention.
This change will take effect the next time the daemons are restarted.

Then we get new settings "for free", the handful of installs that care about this stuff can configure it, and it's out of the way for the 99% of installs that don't care and are happy with the defaults.