This commit reimplements how we monitor Sidekiq processes that are
forked from the Unicorn master process. Prior to this change, we rely on
`Jobs::Heartbeat` to enqueue a `Jobs::RunHeartbeat` job every 3 minutes.
The `Jobs::RunHeartbeat` job then sets a Redis key with a timestamp. In
the Unicorn master process, we then fetch the timestamp that has been set
by the job from Redis every 30 minutes. If the timestamp has not been
updated for more than 30 minutes, we restart the Sidekiq process. The
fundamental flaw with this approach is that it fails to consider
deployments with multiple hosts and multiple Sidekiq processes. A
sidekiq process on a host may be in a bad state but the heartbeat check
will not restart the process because the `Jobs::RunHeartbeat` job is
still being executed by the working Sidekiq processes on other hosts.
In order to properly ensure that stuck Sidekiq processs are restarted,
we now rely on the [Sidekiq::ProcessSet](https://github.com/sidekiq/sidekiq/wiki/API#processes)
API that is supported by Sidekiq. The API provides us with "near real-time (updated every 5 sec)
info about the current set of Sidekiq processes running". The API
provides useful information like the hostname, pid and also when Sidekiq
last did its own heartbeat check. With that information, we can easily
determine if a Sidekiq process needs to be restarted from the Unicorn
master process.
This reduces chances of errors where consumers of strings mutate inputs
and reduces memory usage of the app.
Test suite passes now, but there may be some stuff left, so we will run
a few sites on a branch prior to merging
This adjusts 53d592ad by @tgxworld
- Adds Sidekiq.upause_all! to unpause all sites
- Adds Sidekiq.paused_dbs to list dbs that are currently paused
- Handles some edge cases where unpause thread could extend expiry on
sites that were unpaused from a different process
- Ensures tests always terminates background thread used for pause
keepalive
If sidekiq is paused or Discourse is in readonly continue to queue
heartbeats
If we do not do that then a master process can end up reaping sidekiq
workers and causing various badness
This also impacts restore which can do weird stuff TM in cases like this
Alan Guo Xiang Tan
Jarek Radosz
David Taylor
Joffrey JAFFEUX
Sam Saffron
Guo Xiang Tan
Régis Hanol