Big insert effectively prevents any getPage requests

[kelvich]

If we run insert in one session:

create table t2 as select generate_series(1,10000000000);

and concurrently try get some uncached pages from the pageserver:

\d+

second backend will fail with:

ERROR:  could not read block 0 in rel 1663/16385/1255.0 from page server at lsn 0/3E5FC238
DETAIL:  page server returned error: Timed out while waiting for WAL record at LSN 0/3E5FC238 to arrive, last_record_lsn 0/1043E8D8 disk consistent LSN=0/1695D48

[knizhnik]

All back-pressure thresholds are disabled.
Isn't it expected behavior in this case?

[kelvich]

cc @ololobus https://github.com/zenithdb/console/issues/562

[ololobus]

Yeah, will do it asap

[ololobus]

Backpressure should be turned on on both staging and prod, so it's worth trying similar test again

[hlinnaka]

I can still reproduce this. My hunch is lock starvation in the pageserver, but needs to be investigated.

[knizhnik]

As it was written in comment to backpressure settings, WAL replay speed is about 10Mb/sec.
Current default setting for "max_replication_write_lag" is 500Mb. Which should provide maximal wait lsn time about 50 sec (< 60 sec). But actually with safekeeper at my notebook speed is slower and 500MB write_lag really timeout expiration and so read errors. So to prevent noticeable delays (> 1 seconds) we should not use write_lag > 10Mb. At least in production.
I can create PR for it, changing default value in compute.rs. But console has its own limits...

[stepashka]

could you help reproduce and propose the solution, @MMeent ?

[shanyp]

@jcsp is this still the case after the batch ingestion contributer pr ?

[jcsp]

The original report is from almost two years ago, so I don't think we can say much without re-testing this.