Clean up TAP tests' usage of wait_for_catchup().
By default, wait_for_catchup() waits for the replication connection
to reach the primary's write LSN. That's fine, but in an apparent
attempt to save one query round-trip, it was coded so that we
executed pg_current_wal_lsn() again during each probe query.
Thus, we presented the standby with a moving target to be reached.
(While the test script itself couldn't be causing the write LSN
to advance while it's blocked in wait_for_catchup(), it's plenty
plausible that background activity such as autovacuum is emitting
more WAL.) That could make the test take longer than necessary,
and potentially it could mask bugs by allowing the standby to process
more WAL than a strict interpretation of the test scenario allows.
So, change wait_for_catchup() to do it "by the book", explicitly
collecting the write LSN to wait for at the outset.
Also, various call sites were instructing wait_for_catchup() to
wait for the standby to reach the primary's insert LSN rather than
its write LSN. This also seems like a bad idea. While in most
test scenarios those are the same, if they are different then the
inserted-but-not-yet-written WAL is not presently available to the
standby. The test isn't doing anything to make it become so, so
again we have the potential for unwanted test delay, perhaps even
a test timeout. (Again, background activity would be needed to
make this more than a hypothetical problem.) Hence, change the
callers where necessary so that the wait target is always the
primary's write LSN.
While at it, simplify callers by making use of wait_for_catchup's
default arguments wherever possible (the preceding change makes
this possible in more places than it was before). And rewrite
wait_for_catchup's documentation a bit.
Patch by me; thanks to Julien Rouhaud for review.
Discussion: https://postgr.es/m/2368336.1641843098@sss.pgh.pa.us
Branch
------
master
Details
-------
https://git.postgresql.org/pg/commitdiff/ed48e3582e8447cb9969c366e46c82a56b7608cd
Modified Files
--------------
src/bin/pg_basebackup/t/020_pg_receivewal.pl | 2 +-
src/bin/pg_rewind/t/007_standby_source.pl | 8 ++---
src/bin/pg_rewind/t/008_min_recovery_point.pl | 6 ++--
src/test/perl/PostgreSQL/Test/Cluster.pm | 38 +++++++++++-----------
src/test/recovery/t/001_stream_rep.pl | 25 +++++++-------
src/test/recovery/t/004_timeline_switch.pl | 9 ++---
.../recovery/t/010_logical_decoding_timelines.pl | 3 +-
src/test/recovery/t/012_subtransactions.pl | 9 ++---
src/test/recovery/t/015_promotion_pages.pl | 4 +--
src/test/recovery/t/016_min_consistency.pl | 4 +--
src/test/recovery/t/019_replslot_limit.pl | 17 ++++------
src/test/recovery/t/021_row_visibility.pl | 15 +++------
src/test/recovery/t/025_stuck_on_old_timeline.pl | 3 +-
13 files changed, 59 insertions(+), 84 deletions(-)
