The previous method for doing that was to write zeroes into a
predetermined set of page locations. However, there's a roughly
1-in-64K chance that the existing checksum will match by chance,
and yesterday several buildfarm animals started to reproducibly
see that, resulting in test failures because no checksum mismatch
was reported.
Since the checksum includes the page LSN, test success depends on
the length of the installation's WAL history, which is affected by
(at least) the initial catalog contents, the set of locales installed
on the system, and the length of the pathname of the test directory.
Sooner or later we were going to hit a chance match, and today is
that day.
Harden these tests by specifically inverting the checksum field and
leaving all else alone, thereby guaranteeing that the checksum is
incorrect.
In passing, fix places that were using seek() to set up for syswrite(),
a combination that the Perl docs very explicitly warn against. We've
probably escaped problems because no regular buffered I/O is done on
these filehandles; but if it ever breaks, we wouldn't deserve or get
much sympathy.
Although we've only seen problems in HEAD, now that we recognize the
environmental dependencies it seems like it might be just a matter
of time until someone manages to hit this in back-branch testing.
Hence, back-patch to v11 where we started doing this kind of test.
Discussion: https://postgr.es/m/3192026.1648185780@sss.pgh.pa.us
Slow hosts may avoid load-induced, spurious failures by setting
environment variable PG_TEST_TIMEOUT_DEFAULT to some number of seconds
greater than 180. Developers may see faster failures by setting that
environment variable to some lesser number of seconds. In tests, write
$PostgreSQL::Test::Utils::timeout_default wherever the convention has
been to write 180. This change raises the default for some briefer
timeouts. Back-patch to v10 (all supported versions).
Discussion: https://postgr.es/m/20220218052842.GA3627003@rfd.leadboat.com
Following migration of Windows buildfarm members running TAP tests to
use of ucrt64 perl for those tests, special processing for msys perl is
no longer necessary and so is removed.
Backpatch to release 10
Discussion: https://postgr.es/m/c65a8781-77ac-ea95-d185-6db291e1baeb@dunslane.net
Commits 6c4a8903b et al. had a couple of deficiencies:
* The logic I added to Cluster::start to see if a PID file is present
could be fooled by a stale PID file left over from a previous
postmaster. To fix, if we're not sure whether we expect to find a
running postmaster or not, validate the PID using "kill 0".
* 017_shm.pl has a loop in which it just issues repeated Cluster::start
calls; this will fail if some invocation fails but leaves self->_pid
set. Per buildfarm results, the above fix is not enough to make this
safe: we might have "validated" a PID for a postmaster that exits
immediately after we look. Hence, match each failed start call with
a stop call that will get us back to the self->_pid == undef state.
Add a fail_ok option to Cluster::stop to make this work.
Discussion: https://postgr.es/m/CA+hUKGKV6fOHvfiPt8=dOKzvswjAyLoFoJF1iQXMNpi7+hD1JQ@mail.gmail.com
"pg_ctl start" might start a new postmaster and then return failure
anyway, for example if PGCTLTIMEOUT is exceeded. If there is a
postmaster there, it's still incumbent on us to shut it down at
script end, so check for the PID file even though we are about
to fail.
This has been broken all along, so back-patch to all supported branches.
Discussion: https://postgr.es/m/647439.1642622744@sss.pgh.pa.us
Commits fdd965d07 and 3cd9c3b92 tested CREATE INDEX CONCURRENTLY by
launching two separate pgbench runs concurrently. This was needed so
that only a single client thread would run CREATE INDEX CONCURRENTLY,
avoiding deadlock between two CICs. However, there's a better way,
which is to use an advisory lock to prevent concurrent CICs. That's
better in part because the test code is shorter and more readable, but
mostly because it automatically scales things to launch an appropriate
number of CICs relative to the number of INSERT transactions.
As committed, typically half to three-quarters of the CIC transactions
were pointless because the INSERT transactions had already stopped.
In passing, remove background_pgbench, which was added to support
these tests and isn't needed anymore. We can always put it back
if we find a use for it later.
Back-patch to v12; older pgbench versions lack the
conditional-execution features needed for this method.
Tom Lane and Andrey Borodin
Discussion: https://postgr.es/m/139687.1635277318@sss.pgh.pa.us
The purpose of commit 8a54e12a38 was to
fix this, and it sufficed when the PREPARE TRANSACTION completed before
the CIC looked for lock conflicts. Otherwise, things still broke. As
before, in a cluster having used CIC while having enabled prepared
transactions, queries that use the resulting index can silently fail to
find rows. It may be necessary to reindex to recover from past
occurrences; REINDEX CONCURRENTLY suffices. Fix this for future index
builds by making CIC wait for arbitrarily-recent prepared transactions
and for ordinary transactions that may yet PREPARE TRANSACTION. As part
of that, have PREPARE TRANSACTION transfer locks to its dummy PGPROC
before it calls ProcArrayClearTransaction(). Back-patch to 9.6 (all
supported versions).
Andrey Borodin, reviewed (in earlier versions) by Andres Freund.
Discussion: https://postgr.es/m/01824242-AA92-4FE9-9BA7-AEBAFFEA3D0C@yandex-team.ru
CIC and REINDEX CONCURRENTLY assume backends see their catalog changes
no later than each backend's next transaction start. That failed to
hold when a backend absorbed a relevant invalidation in the middle of
running RelationBuildDesc() on the CIC index. Queries that use the
resulting index can silently fail to find rows. Fix this for future
index builds by making RelationBuildDesc() loop until it finishes
without accepting a relevant invalidation. It may be necessary to
reindex to recover from past occurrences; REINDEX CONCURRENTLY suffices.
Back-patch to 9.6 (all supported versions).
Noah Misch and Andrey Borodin, reviewed (in earlier versions) by Andres
Freund.
Discussion: https://postgr.es/m/20210730022548.GA1940096@gust.leadboat.com
Incrementing the level of the call stack reported is useful for
debugging purposes as it allows to control which part of the test is
exactly failing, especially if a test is structured with subroutines
that call routines from Test::More.
This adds more incrementations of $Test::Builder::Level where debugging
gets improved (for example it does not make sense for some paths like
pg_rewind where long subroutines are used).
A note is added to src/test/perl/README about that, based on a
suggestion from Andrew Dunstan and a wording coming from both of us.
Usage of Test::Builder::Level has spread in 12, so a backpatch down to
this version is done.
Reviewed-by: Andrew Dunstan, Peter Eisentraut, Daniel Gustafsson
Discussion: https://postgr.es/m/YV1CCFwgM1RV1LeS@paquier.xyz
Backpatch-through: 12
3c5b0685b9 used setFilePointer() to set the position of the filehandle, but
passed the wrong filehandle, always leaving the position at 0. Instead of just
fixing that, remove use of setFilePointer(), we have a perl fd at this point,
so we can just use perl's seek().
Additionally, the perl filehandle wasn't closed, just the windows filehandle.
Reviewed-By: Andrew Dunstan <andrew@dunslane.net>
Author: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/20211003173038.64mmhgxctfqn7wl6@alap3.anarazel.de
Backpatch: 9.6-, like 3c5b0685b9
Contrary to the output of native perl, Msys perl generates outputs with
CRLFs characters. There are already places in the TAP code where CRLFs
(\r\n) are automatically converted to LF (\n) on Msys, but we missed a
couple of places when running commands and using their output for
comparison, that would lead to failures.
This problem has been found thanks to the test added in 5adb067 using
TestLib::command_checks_all(), but after a closer look more code paths
were missing a filter.
This is backpatched all the way down to prevent any surprises if a new
test is introduced in stable branches.
Reviewed-by: Andrew Dunstan, Álvaro Herrera
Discussion: https://postgr.es/m/1252480.1631829409@sss.pgh.pa.us
Backpatch-through: 9.6
This is similar to the work done in 8279f68 for TestLib.pm, where
environment variables set may cause unwanted failures if using a
temporary installation with pg_regress. The list of variables reset is
adjusted in each stable branch depending on what is supported.
Comments are added to remember that the lists in TestLib.pm and
pg_regress.c had better be kept in sync.
Reviewed-by: Álvaro Herrera
Discussion: https://postgr.es/m/YMNR9GYDn+fHlMta@paquier.xyz
Backpatch-through: 9.6
Several TAP tests use poll_query_until() to wait for the postmaster
to restart. They were checking to see if a trivial query
(e.g. "SELECT 1") succeeds. However, that's problematic in the wake
of commit 11e9caff8, because now that we feed said query to psql
via stdin, we risk IPC::Run whining about a SIGPIPE failure if psql
quits before reading the query. Hence, we can't use a nonempty
query in cases where we need to wait for connection failures to
stop happening.
Per the precedent of commits c757a3da0 and 6d41dd045, we can pass
"undef" as the query in such cases to ensure that IPC::Run has
nothing to write. However, then we have to say that the expected
output is empty, and this exposes a deficiency in poll_query_until:
if psql fails altogether and returns empty stdout, poll_query_until
will treat that as a success! That's because, contrary to its
documentation, it makes no actual check for psql failure, looking
neither at the exit status nor at stderr.
To fix that, adjust poll_query_until to insist on empty stderr as
well as a stdout match. (I experimented with checking exit status
instead, but it seems that psql often does exit(1) in cases that we
need to consider successes. That might be something to fix someday,
but it would be a non-back-patchable behavior change.)
Back-patch to v10. The test cases needing this exist only as far
back as v11, but it seems wise to keep poll_query_until's behavior
the same in v10, in case we back-patch another such test case in
future. (9.6 does not currently need this change, because in that
branch poll_query_until can't be told to accept empty stdout as
a success case.)
Per assorted buildfarm failures, mostly on hoverfly.
Discussion: https://postgr.es/m/CAA4eK1+zM6L4QSA1XMvXY_qqWwdUmqkOS1+hWvL8QcYEBGA1Uw@mail.gmail.com
This variable was present in the list added by 9d660670, but it is not
supported by this branch. Issue noticed while diving into a similar
change for pg_regress.c.
Backpatch-through: 9.6
The Msys shell mangles certain patterns in its command line, so avoid
handing arbitrary SQL to psql on the command line and instead use
IPC::Run's redirection facility for stdin. This pattern is already
mostly whats used, but query_poll_until() was not doing the right thing.
Problem discovered on the buildfarm when a new TAP test failed on msys.
Various environment variables were not getting reset in the TAP tests,
which would cause failures depending on the tests or the environment
variables involved. For example, PGSSL{MAX,MIN}PROTOCOLVERSION could
cause failures in the SSL tests. Even worse, a junk value of
PGCLIENTENCODING makes a server startup fail. The list of variables
reset is adjusted in each stable branch depending on what is supported.
While on it, simplify a bit the code per a suggestion from Andrew
Dunstan, using a list of variables instead of doing single deletions.
Reviewed-by: Andrew Dunstan, Daniel Gustafsson
Discussion: https://postgr.es/m/YLbjjRpucIeZ78VQ@paquier.xyz
Backpatch-through: 9.6
In order to avoid getting old logfile contents certain functions in
PostgresNode were doing one of two things. On Windows it rotated the
logfile and restarted the server, while elsewhere it truncated the log
file. Both of these are unnecessary. We borrow from the buildfarm which
does this instead: note the size of the logfile before we start, and
then when fetching the logfile skip to that position before accumulating
contents. This is spelled differently on Windows but the effect is the
same. This is largely centralized in TestLib's slurp_file function,
which has a new optional parameter, the offset to skip to before
starting to reading the file. Code in the client becomes much neater.
Backpatch to all live branches.
Michael Paquier, slightly modified by me.
Discussion: https://postgr.es/m/YHajnhcMAI3++pJL@paquier.xyz
Commit 151c0c5f7 neglected the possibility that a TEMP_CONFIG file
would explicitly set max_wal_senders=0; as indeed buildfarm member
thorntail does, so that it can test wal_level=minimal in other test
suites. Hence, rather than assuming that max_wal_senders=10 will
prevail if we say nothing, set it explicitly.
Set max_replication_slots=10 explicitly too, just to be safe.
Back-patch to v10, like the previous patch.
Discussion: https://postgr.es/m/723911.1601417626@sss.pgh.pa.us
PostgresNode.pm set "max_wal_senders = 5" for replication testing,
but this seems to be slightly too low for our current test suite.
Slower buildfarm members frequently report "number of requested standby
connections exceeds max_wal_senders" failures, due to old walsenders
not exiting instantaneously. Usually, the test does not fail overall
because of automatic walreceiver restart, but sometimes the failure
becomes visible; and in any case such retries slow down the test.
That value came in with commit 89ac7004d, but was soon obsoleted by
f6d6d2920, which raised the built-in default from zero to 10; so that
PostgresNode.pm is actually setting it to less than the conservative
built-in default. That seems pretty pointless, so let's remove the
special setting and let the default prevail, in hopes of making
the TAP tests more robust.
Likewise, the setting "max_replication_slots = 5" is obsolete and
can be removed.
While here, reverse-engineer a comment about why we're choosing
less-than-default values for some other settings.
(Note: before v12, max_wal_senders counted against max_connections
so that the latter setting also needs some fiddling with.)
Back-patch to v10 where the subscription tests were added.
It's likely that the older branches aren't pushing the boundaries
of max_wal_senders, but I'm disinclined to spend time trying to
figure out exactly when it started to be a problem.
Discussion: https://postgr.es/m/723911.1601417626@sss.pgh.pa.us
PostgresNode already retained base directories in such cases. Stop
using $SIG{__DIE__}, which is redundant with the exit status check, in
lieu of proliferating it to TestLib. Back-patch to 9.6, where commit
88802e0680 introduced retention on
failure.
Reviewed by Daniel Gustafsson.
Discussion: https://postgr.es/m/20200202170155.GA3264196@rfd.leadboat.com
src/test/kerberos and src/test/ldap need to run a private authentication
server of the relevant type, for which they need a free TCP port.
They were just picking a random port number in 48K-64K, which works
except when something's already using the particular port. Notably,
the probability of failure rises dramatically if one simply runs those
tests in a tight loop, because each test cycle leaves behind a bunch of
high ports that are transiently in TIME_WAIT state.
To fix, split out the code that PostgresNode.pm already had for
identifying a free TCP port number, so that it can be invoked to choose
a port for the KDC or LDAP server. This isn't 100% bulletproof, since
conceivably something else on the machine could grab the port between
the time we check and the time we actually start the server. But that's
a pretty short window, so in practice this should be good enough.
Back-patch to v11 where these test suites were added.
Patch by me, reviewed by Andrew Dunstan.
Discussion: https://postgr.es/m/3397.1564872168@sss.pgh.pa.us
This fixes some TAP suites when using msys Perl and a builddir located
in an msys mount point other than "/". For example, builddir=/c/pg
exhibited the problem, since /c/pg falls in mount point "/c".
Back-patch to 9.6, where tests first started to perform such
translations. In back branches, offer both new and old APIs.
Reviewed by Andrew Dunstan.
Discussion: https://postgr.es/m/20190610045838.GA238501@rfd.leadboat.com
The buildfarm client uses TEMP_CONFIG to implement its extra_config
setting. Except for stats_temp_directory, extra_config now applies to
TAP suites; extra_config values seen in the past month are compatible
with this. Back-patch to 9.6, where PostgresNode was introduced, so the
buildfarm can rely on it sooner.
Reviewed by Andrew Dunstan and Tom Lane.
Discussion: https://postgr.es/m/20181229021950.GA3302966@rfd.leadboat.com
Commit c0985099, later adjusted by commit 4ab02e81, probed 0.0.0.0
in addition to 127.0.0.1, for the benefit of Windows build farm
animals. It isn't really useful on Unix systems, and turned out to
be a bit inconvenient to users of some corporate firewall software.
Switch back to probing just 127.0.0.1 on non-Windows systems.
Back-patch to 9.6, like the earlier changes.
Discussion: https://postgr.es/m/CA%2BhUKG%2B21EPwfgs4m%2BtqyRtbVqkOUvP8QQ8sWk9%2Bh55Aub1H3A%40mail.gmail.com
Commit c098509927 changed
PostgresNode::get_new_node() to probe 0.0.0.0 instead of 127.0.0.1, but
the new test was less effective for Windows native Perl. This increased
the failure rate of buildfarm members bowerbird and jacana. Instead,
test 0.0.0.0 and concrete addresses. This restores the old level of
defense, but the algorithm is still subject to its longstanding time of
check to time of use race condition. Back-patch to 9.6, like the
previous change.
Discussion: https://postgr.es/m/GrdLgAdUK9FdyZg8VIcTDKVOkys122ZINEb3CjjoySfGj2KyPiMKTh1zqtRp0TAD7FJ27G-OBB3eplxIB5GhcQH5o8zzGZfp0MuJaXJxVxk=@yesql.se
Up to now the tests of pg_rewind have been using a superuser for all its
tests (which is the default of many tests actually, and something that
ought to be reviewed) when involving an online source server, still it
is possible to use a non-superuser role to do that as long as this role
is granted permissions to execute all the source-side functions used for
the rewind. This is possible since v11, and was already documented as
of bfc8068.
PostgresNode::init is extended so as callers of this routine can add
extra options to configure the authentication of a new node, which gets
used by this commit, and allows the tests to work properly on Windows
where SSPI is used.
This will allow to catch up easily any change in pg_rewind if the tool
begins to use more backend-side functions, so as the properties
introduced by v11 are kept.
Per suggestion from Peter Eisentraut.
Author: Michael Paquier
Reviewed-by: Magnus Hagander
Discussion: https://postgr.es/m/20190411041336.GM2728@paquier.xyz
postmaster startup scrutinizes any shared memory segment recorded in
postmaster.pid, exiting if that segment matches the current data
directory and has an attached process. When the postmaster.pid file was
missing, a starting postmaster used weaker checks. Change to use the
same checks in both scenarios. This increases the chance of a startup
failure, in lieu of data corruption, if the DBA does "kill -9 `head -n1
postmaster.pid` && rm postmaster.pid && pg_ctl -w start". A postmaster
will no longer stop if shmat() of an old segment fails with EACCES. A
postmaster will no longer recycle segments pertaining to other data
directories. That's good for production, but it's bad for integration
tests that crash a postmaster and immediately delete its data directory.
Such a test now leaks a segment indefinitely. No "make check-world"
test does that. win32_shmem.c already avoided all these problems. In
9.6 and later, enhance PostgresNode to facilitate testing. Back-patch
to 9.4 (all supported versions).
Reviewed (in earlier versions) by Daniel Gustafsson and Kyotaro HORIGUCHI.
Discussion: https://postgr.es/m/20190408064141.GA2016666@rfd.leadboat.com
postmaster startup scrutinizes any shared memory segment recorded in
postmaster.pid, exiting if that segment matches the current data
directory and has an attached process. When the postmaster.pid file was
missing, a starting postmaster used weaker checks. Change to use the
same checks in both scenarios. This increases the chance of a startup
failure, in lieu of data corruption, if the DBA does "kill -9 `head -n1
postmaster.pid` && rm postmaster.pid && pg_ctl -w start". A postmaster
will no longer recycle segments pertaining to other data directories.
That's good for production, but it's bad for integration tests that
crash a postmaster and immediately delete its data directory. Such a
test now leaks a segment indefinitely. No "make check-world" test does
that. win32_shmem.c already avoided all these problems. In 9.6 and
later, enhance PostgresNode to facilitate testing. Back-patch to 9.4
(all supported versions).
Reviewed by Daniel Gustafsson and Kyotaro HORIGUCHI.
Discussion: https://postgr.es/m/20130911033341.GD225735@tornado.leadboat.com
This unifies the various ad hoc logging (message printing, error
printing) systems used throughout the command-line programs.
Features:
- Program name is automatically prefixed.
- Message string does not end with newline. This removes a common
source of inconsistencies and omissions.
- Additionally, a final newline is automatically stripped, simplifying
use of PQerrorMessage() etc., another common source of mistakes.
- I converted error message strings to use %m where possible.
- As a result of the above several points, more translatable message
strings can be shared between different components and between
frontends and backend, without gratuitous punctuation or whitespace
differences.
- There is support for setting a "log level". This is not meant to be
user-facing, but can be used internally to implement debug or
verbose modes.
- Lazy argument evaluation, so no significant overhead if logging at
some level is disabled.
- Some color in the messages, similar to gcc and clang. Set
PG_COLOR=auto to try it out. Some colors are predefined, but can be
customized by setting PG_COLORS.
- Common files (common/, fe_utils/, etc.) can handle logging much more
simply by just using one API without worrying too much about the
context of the calling program, requiring callbacks, or having to
pass "progname" around everywhere.
- Some programs called setvbuf() to make sure that stderr is
unbuffered, even on Windows. But not all programs did that. This
is now done centrally.
Soft goals:
- Reduces vertical space use and visual complexity of error reporting
in the source code.
- Encourages more deliberate classification of messages. For example,
in some cases it wasn't clear without analyzing the surrounding code
whether a message was meant as an error or just an info.
- Concepts and terms are vaguely aligned with popular logging
frameworks such as log4j and Python logging.
This is all just about printing stuff out. Nothing affects program
flow (e.g., fatal exits). The uses are just too varied to do that.
Some existing code had wrappers that do some kind of print-and-exit,
and I adapted those.
I tried to keep the output mostly the same, but there is a lot of
historical baggage to unwind and special cases to consider, and I
might not always have succeeded. One significant change is that
pg_rewind used to write all error messages to stdout. That is now
changed to stderr.
Reviewed-by: Donald Dong <xdong@csumb.edu>
Reviewed-by: Arthur Zakirov <a.zakirov@postgrespro.ru>
Discussion: https://www.postgresql.org/message-id/flat/6a609b43-4f57-7348-6480-bd022f924310@2ndquadrant.com
When libpq is loaded in the server (for instance, by
libpqwalreceiver), it may use libpq environment variables set in the
postmaster environment for connection parameter defaults. This has
some confusing effects in our test suites. For example, the TAP test
infrastructure sets PGAPPNAME to allow identifying clients in the
server log. But this environment variable is also inherited by
temporary servers started with pg_ctl and is then in turn used by
libpqwalreceiver as the application_name for connecting to remote
servers where it then shows up in pg_stat_replication and is relevant
for things like synchronous_standby_names. Replication already has a
suitable default for application_name, and overriding that
accidentally then requires the individual test cases to re-override
that, which is all very confusing and unnecessary.
To fix, unset PGAPPNAME temporarily before running pg_ctl start or
restart in the tests.
More comprehensive approaches like unsetting all environment variables
in pg_ctl were considered but might be too complicated to achieve
portably.
The now unnecessary re-overriding of application_name by test cases is
also removed.
Reviewed-by: Noah Misch <noah@leadboat.com>
Discussion: https://www.postgresql.org/message-id/flat/33383613-690e-6f1b-d5ba-4957ff40f6ce@2ndquadrant.com
c186ba13 has fixed an issue related to the updates of the minimum
recovery LSN across multiple processes on standbys, but we never really
had a test case able to reliably check its logic.
This commit introduces a new test case to close the gap, and is designed
to check the consistency of data based on the minimum recovery point set
by either the startup process or the checkpointer for both an offline
cluster (by looking at the on-disk page headers) and an online cluster
(using pageinspect).
Note that with c186ba13 reverted, this test fails badly for both the
online and offline cases, as designed.
Author: Michael Paquier, Andrew Gierth
Reviewed-by: Andrew Gierth, Georgios Kokolatos, Arthur Zakirov
Discussion: https://postgr.es/m/20181108044525.GA17482@paquier.xyz
recovery.conf settings are now set in postgresql.conf (or other GUC
sources). Currently, all the affected settings are PGC_POSTMASTER;
this could be refined in the future case by case.
Recovery is now initiated by a file recovery.signal. Standby mode is
initiated by a file standby.signal. The standby_mode setting is
gone. If a recovery.conf file is found, an error is issued.
The trigger_file setting has been renamed to promote_trigger_file as
part of the move.
The documentation chapter "Recovery Configuration" has been integrated
into "Server Configuration".
pg_basebackup -R now appends settings to postgresql.auto.conf and
creates a standby.signal file.
Author: Fujii Masao <masao.fujii@gmail.com>
Author: Simon Riggs <simon@2ndquadrant.com>
Author: Abhijit Menon-Sen <ams@2ndquadrant.com>
Author: Sergei Kornilov <sk@zsrv.org>
Discussion: https://www.postgresql.org/message-id/flat/607741529606767@web3g.yandex.ru/
Reporting only the stderr is unhelpful when the problem is that the
server output we're getting doesn't match what was expected. So we
should report the query output too; and just for good measure, let's
print the query we used and the output we expected.
Back-patch to 9.5 where poll_query_until was introduced.
Discussion: https://postgr.es/m/17913.1539634756@sss.pgh.pa.us
Buildfarm member tern failed src/bin/pg_ctl/t/001_start_stop.pl when a
check_mode_recursive() call overlapped a server's startup-time deletion
of pg_stat/global.stat. Just warn. Also, include errno in the message.
Back-patch to v11, where check_mode_recursive() first appeared.
Currently there are two ways to trigger log rotation in logging collector
process: call pg_rotate_logfile() SQL-function or send SIGUSR1 signal directly
to logging collector process. However, it's nice to have more suitable way
for external tools to do that, which wouldn't require SQL connection or
knowledge of logging collector pid. This commit implements triggering log
rotation by "pg_ctl logrotate" command.
Discussion: https://postgr.es/m/20180416.115435.28153375.horiguchi.kyotaro%40lab.ntt.co.jp
Author: Kyotaro Horiguchi, Alexander Kuzmenkov, Alexander Korotkov
