Upgrade etherpad.wikimedia.org to the most recent version (v1.9.7).
Preparation work:
[x] build new etherpad-lite Debian package for `1.9.7`
[x] build new `prometheus-etherpad-exporter` package
[x] prepare new etherpad VM (bookworm, etherpad1004)
[x] test etherpad-lite 1.9.7 on devtools
[x] installation works (puppet run and installation for 1.9.7 + exporter)
[x] mysql and proxy are missing
[x] apply `role(etherpad)` to `etherpad1004` **and** set `profile::etherpad::service_ensure: stopped` for `etherpad1004`
[x] run puppet on `etherpad1004` and verify successful installation
[x] make [Grafana dashboard](https://grafana-rw.wikimedia.org/d/000000193/etherpad?orgId=1&var-node=etherpad1003) compatible with multiple etherpad instances
[] announce maintenance windows some days in advance
Maintenance (switch from `etherpad1003` to `etherpad1004`):
[] create a downtime for `etherpad1003`
[] **stop etherpad-lite.service** on `etherpad1003` (set `profile::etherpad::service_ensure: stopped` or **stop** vm) https://gerrit.wikimedia.org/r/1005961
[] wait until etherpad-lite is stopped properly,
[] set `profile::etherpad::service_ensure: running` for `etherpad1004` https://gerrit.wikimedia.org/r/1005962
[] run puppet on `etherpad1004` and verify puppet agent logs
[] change `etherpad.wmnet` CNAME to `etherpad1004.eqiad.wmnet` and run authdns-update
[] wait 300s for DNS cache
[] visit https://etherpad.wikimedia.org and check if etherpad still works
[] open old pads
[] create new pads
[] check [metrics](https://grafana.wikimedia.org/d/000000193/etherpad?orgId=1)
After maintenance:
[] stop `etherpad1003` and decommission after grace period
[] create followup tickets for etherpad replica in codfw