For such issues, I find this view very useful (the first one):
Examine blocking_pid's , and tell us what kind of operation is blocking
the other processes . Also, are there many long running transactions in
2018-03-06 21:24 GMT-06:00 Scott Frazer <sfra...@couponcabin.com>:
> Hi, we have a Postgres 9.6 setup using replication that has recently
> started seeing a lot of processes stuck in "SubtransControlLock" as a
> wait_event on the read-replicas. Like this, only usually about 300-800 of
> 179706 | LWLockNamed | SubtransControlLock
> 186602 | LWLockNamed | SubtransControlLock
> 186606 | LWLockNamed | SubtransControlLock
> 180947 | LWLockNamed | SubtransControlLock
> 186621 | LWLockNamed | SubtransControlLock
> The server then begins to crawl, with some queries just never finishing
> until I finally shut the server down.
> Searching for that particular combo of wait_event_type and wait_event only
> seems to turn up the page about statistics collection, but no helpful
> information on troubleshooting this lock.
> Restarting the replica server clears the locks and allows us to start
> working again, but it's happened twice now in 12 hours and I'm worried it
> will happen again.
> Does anyone have any advice on where to start looking?
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