At 18:00 UTC all parsercache hosts experienced a sudden increase in connections:
While the connections dropped to more normal values at around 19:11 UTC, they are still a bit over normal values.
The load hit pc1008 harder than other hosts, and it was depooled and we pooled pc1010 instead: https://gerrit.wikimedia.org/r/#/c/operations/mediawiki-config/+/580117/
pc1010 seemed to behave better than pc1008, which will be troubleshooted separately at T247787
The reason for this sudden connection increase is still unknown and needs to be researched
At around 19:16, however, we see a big increase on writes which is still on-going