The CI has reported that using a marker to force the output of the
detach step to happen after the wait step was not enough, as
isolationtester has managed to report the detach step as waiting before
the wait step finishes in some runs.
src/test/isolation/README tells that there is a more drastic method to
enforce the ordering of the output: an empty step positioned just after
the wait step can force the wait step to complete before the detach step
begins. This method has been able to pass 10 runs in the CI here, while
HEAD seems to fail 15~20% of the time in the CF bot.
Discussion: https://postgr.es/m/Z6WO8FbqK_FHmrzC@paquier.xyz
This test has been disabled in 9f00edc22888 due to an instable expected
output, where it would be possible for the wait step to report its
result after the detach step is done. The expected output was ordered
so as the detach would always report last.
Isolation test permutations have the option to use markers to control
the ordering for cases like this one, as documented in
src/test/isolation/README. The permutation is enabled once again, this
time with a marker added so as the detach step reports only once the
wait step has finished, ensuring a correct output ordering.
Reviewed-by: Bertrand Drouvot
Discussion: https://postgr.es/m/Z6MBZTX5EqQ6A8Zc@paquier.xyz
This serves as an example of how to use the new function introduced in
ce5c620fb625, pgstat_drop_matching_entries(), with a callback able to
filter the entries dropped.
A SQL function named injection_points_stats_drop() is added with some
tests.
Author: Lukas Fitti
Discussion: https://postgr.es/m/CAP53PkwuFbo3NkwZgxwNRMjMfqPEqidD-SggaoQ4ijotBVLJAA@mail.gmail.com
The right mix of DDL and VACUUM could corrupt a catalog page header such
that PageIsVerified() durably fails, requiring a restore from backup.
This affects only catalogs that both have a syscache and have DDL code
that uses syscache tuples to construct updates. One of the test
permutations shows a variant not yet fixed.
This makes !TransactionIdIsValid(TM_FailureData.xmax) possible with
TM_Deleted. I think core and PGXN are indifferent to that.
Per bug #17821 from Alexander Lakhin. Back-patch to v13 (all supported
versions). The test case is v17+, since it uses INJECTION_POINT.
Discussion: https://postgr.es/m/17821-dd8c334263399284@postgresql.org
Directory "injection_points" has specified NO_INSTALLCHECK since before
commit c35f419d6efbdf1a050250d84b687e6705917711 added the specs, but
that commit neglected to disable the corresponding meson runningcheck.
The alternative would be to enable "make installcheck" for ISOLATION,
but the GNU make build system lacks a concept of setting NO_INSTALLCHECK
for REGRESS without also setting it for ISOLATION. Back-patch to v17,
where that commit first appeared, to avoid surprises when back-patching
additional specs.
Discussion: https://postgr.es/m/17821-dd8c334263399284@postgresql.org
As coded, the module was not using pending entries to store its data
locally before doing a flush to the central dshash with a timed
pgstat_report_stat() call. Hence, the flush callback was defined, but
finished by being not used. As a template, this is more efficient than
the original logic of updating directly the shared memory entries as
this reduces the interactions that need to be done with the pgstats
hash table in shared memory.
injection_stats_flush_cb() was also missing a pgstat_unlock_entry(), so
add one, while on it.
Reviewed-by: Bertrand Drouvot
Discussion: https://postgr.es/m/Z3JbLhKFFm6kKfT8@ip-10-97-1-34.eu-west-3.compute.internal
This new field controls if entries of a stats kind should be written or
not to the on-disk pgstats file when shutting down an instance. This
affects both fixed and variable-numbered kinds.
This is useful for custom statistics by itself, and a patch is under
discussion to add a new builtin stats kind where the write of the stats
is not necessary. All the built-in stats kinds, as well as the two
custom stats kinds in the test module injection_points, set this flag to
"true" for now, so as stats entries are written to the on-disk pgstats
file.
Author: Bertrand Drouvot
Reviewed-by: Nazir Bilal Yavuz
Discussion: https://postgr.es/m/Zz7T47nHwYgeYwOe@ip-10-97-1-34.eu-west-3.compute.internal
9f00edc22888 has disabled a permutation due to failures in the CI for
FreeBSD environments, but this is a matter of timing. Let's document
properly why this type of permutation is a bad idea if relying on a wait
done in a SQL function, so as this can be avoided when implementing new
tests (this spec is also a template).
Reviewed-by: Bertrand Drouvot
Discussion: https://postgr.es/m/ZyCa2qsopKaw3W3K@paquier.xyz
The first permutation done in the test does a wait, a wakeup then a
detach. It is proving to be unstable in the CI for FreeBSD (Windows and
Linux are stable). The failure shows that the wait is so slow to finish
after being woken up that the detach has the time to finish before the
wait, messing up with the expected output.
There may be a platform-specific issue going on here, but for now
disable this permutation to make the CI runs more stable.
Discussion: https://postgr.es/m/ZxrnSGdNtQWAxE3_@paquier.xyz
This test can act as a template when implementing an isolation test with
injection points, and tracks in a much simpler way some of the behaviors
implied in the existing isolation test "inplace" that has been added in
c35f419d6efb. Particularly, a detach does not affect a backend wait; a
wait needs to be interrupted by a wakeup.
Reviewed-by: Bertrand Drouvot
Discussion: https://postgr.es/m/ZxGTONm_ctQz--io@paquier.xyz
As previously-added tests demonstrated, heap_inplace_update() could
instead update an unrelated tuple of the same catalog. It could lose
the update. Losing relhasindex=t was a source of index corruption.
Inplace-updating commands like VACUUM will now wait for heap_update()
commands like GRANT TABLE and GRANT DATABASE. That isn't ideal, but a
long-running GRANT already hurts VACUUM progress more just by keeping an
XID running. The VACUUM will behave like a DELETE or UPDATE waiting for
the uncommitted change.
For implementation details, start at the systable_inplace_update_begin()
header comment and README.tuplock. Back-patch to v12 (all supported
versions). In back branches, retain a deprecated heap_inplace_update(),
for extensions.
Reported by Smolkin Grigory. Reviewed by Nitin Motiani, (in earlier
versions) Heikki Linnakangas, and (in earlier versions) Alexander
Lakhin.
Discussion: https://postgr.es/m/CAMp+ueZQz3yDk7qg42hk6-9gxniYbp-=bG2mgqecErqR5gGGOA@mail.gmail.com
This opens the possibility to define keys for more types of statistics
kinds in PgStat_HashKey, the first case being 8-byte query IDs for
statistics like pg_stat_statements.
This increases the size of PgStat_HashKey from 12 to 16 bytes, while
PgStatShared_HashEntry, entry stored in the dshash for pgstats, keeps
the same size due to alignment.
xl_xact_stats_item, that tracks the stats items to drop in commit WAL
records, is increased from 12 to 16 bytes. Note that individual chunks
in commit WAL records should be multiples of sizeof(int), hence 8-byte
object IDs are stored as two uint32, based on a suggestion from Heikki
Linnakangas.
While on it, the field of PgStat_HashKey is renamed from "objoid" to
"objid", as for some stats kinds this field does not refer to OIDs but
just IDs, like for replication slot stats.
This commit bumps the following format variables:
- PGSTAT_FILE_FORMAT_ID, as PgStat_HashKey is written to the stats file
for non-serialized stats kinds in the dshash table.
- XLOG_PAGE_MAGIC for the changes in xl_xact_stats_item.
- Catalog version, for the SQL function pg_stat_have_stats().
Reviewed-by: Bertrand Drouvot
Discussion: https://postgr.es/m/ZsvTS9EW79Up8I62@paquier.xyz
As introduced by f9900df5f94, a REINDEX CONCURRENTLY job done for an
index with predicates or expressions would set PROC_IN_SAFE_IC in its
MyProc->statusFlags, causing it to be ignored by other concurrent
operations.
Such concurrent index rebuilds should never be ignored, as a predicate
or an expression could call a user-defined function that accesses a
different table than the table where the index is rebuilt.
A test that uses injection points is added, backpatched down to 17.
Michail has proposed a different test, but I have added something
simpler with more coverage.
Oversight in f9900df5f949.
Author: Michail Nikolaev
Discussion: https://postgr.es/m/CANtu0oj9A3kZVduFTG0vrmGnKB+DCHgEpzOp0qAyOgmks84j0w@mail.gmail.com
Backpatch-through: 14
There were two spots in pgstat_read_statsfile() where is was possible to
finish with a null-pointer-dereference crash for custom pgstats kinds:
- When reading stats for a fixed-numbered stats entry.
- When reading a variable stats entry with name serialization.
For both cases, these issues were reachable by starting a server after
changing shared_preload_libraries so as the stats written previously
could not be loaded.
The code is changed so as the stats are ignored in this case, like the
other code paths doing similar sanity checks. Two WARNINGs are added to
be able to debug these issues. A test is added for the case of
fixed-numbered stats with the module injection_points.
Oversights in 7949d9594582, spotted while looking at a different report.
Discussion: https://postgr.es/m/Ztj0Jftsn4xXuXtl@paquier.xyz
This is confusing, as it exports twice the same variable. Oversight in
6782709df81f that has spread in more places afterwards.
Reported-by: Alvaro Herrera, Tom Lane
Discussion: https://postgr.es/m/202408201630.mn6vbohjh7hh@alvherre.pgsql
Backpatch-through: 17
This GUC controls if cumulative statistics are enabled or not in the
module. Custom statistics require the module to be loaded with
shared_preload_libraries, hence this GUC is made PGC_POSTMASTER. By
default, the stats are disabled. 001_stats.pl is updated to enable the
statistics, as it is the only area where these are required now.
This will be used by an upcoming change for the injection point test
added by 768a9fd5535f where stats should not be used, as the test runs a
point callback in a critical section. And the module injection_points
will need to be loaded with shared_preload_libraries there.
Per discussion with Álvaro Herrera.
Author: Michael Paquier
Discussion: https://postgr.es/m/ZsUnJUlSOBNAzwW1@paquier.xyz
This commits adds callbacks to initialize the shared memory state of the
module when loaded with shared_preload_libraries. This is necessary to
be able to update the test introduced in 768a9fd5535f to use the macros
INJECTION_POINT_{LOAD,CACHED}() rather than a SQL function in the module
injection_points forcing a load, as this test runs a callback in a
critical section where no memory allocation should happen.
Initializing the shared memory state of the module while loading
provides a strict control on the timing of its allocation. If the
module is not loaded at startup, it will use a GetNamedDSMSegment()
instead to initialize its shmem state on-the-fly.
Per discussion with Álvaro Herrera.
Author: Michael Paquier
Discussion: https://postgr.es/m/ZsUnJUlSOBNAzwW1@paquier.xyz
This adds two counters to the fixed-numbered stats of injection points
to track the number of times injection points have been cached and
loaded from the cache, as of the additions coming from a0a5869a8598 and
4b211003ecc2.
These should have been part of f68cd847fa40, but I have lacked time and
energy back then, and it did not prevent the code to be a useful
template.
While on it, this commit simplifies the description of a few tests while
adding coverage for the new stats data.
Author: Yogesh Sharma
Discussion: https://postgr.es/m/3a6977f7-54ab-43ce-8806-11d5e15526a2@catprosystems.com
Like 75534436a477, this acts mainly as a template to show what can be
achieved with fixed-numbered stats (like WAL, bgwriter, etc.) with the
pluggable cumulative statistics APIs introduced in 7949d9594582.
Fixed-numbered stats are defined in their own file, named
injection_stats_fixed.c, separated entirely from the variable-numbered
case in injection_stats.c. This is mainly for clarity as having both
examples in the same file would be confusing.
Note that this commit uses the helper routines added in 2eff9e678d35.
The stats stored track globally the number of times injection points
have been attached, detached or run. Two more fields should be added
later for the number of times a point has been cached or loaded, but
what's here is enough as a template.
More TAP tests are added, providing coverage for fixed-numbered custom
stats.
Author: Michael Paquier
Reviewed-by: Dmitry Dolgov, Bertrand Drouvot
Discussion: https://postgr.es/m/Zmqm9j5EO0I4W8dx@paquier.xyz
This acts as a template of what can be achieved with the pluggable
cumulative stats APIs introduced in 7949d9594582 for the
variable-numbered case where stats entries are stored in the pgstats
dshash, while being potentially useful on its own for injection points,
say to add starting and/or stopping conditions based on the statistics
(want to trigger a callback after N calls, for example?).
Currently, the only data gathered is the number of times an injection
point is run. More fields can always be added as required. All the
routines related to the stats are located in their own file, called
injection_stats.c in the test module injection_points, for clarity.
The stats can be used only if the test module is loaded through
shared_preload_libraries. The key of the dshash uses InvalidOid for the
database, and an int4 hash of the injection point name as object ID.
A TAP test is added to provide coverage for the new custom cumulative
stats APIs, showing the persistency of the data across restarts, for
example.
Author: Michael Paquier
Reviewed-by: Dmitry Dolgov, Bertrand Drouvot
Discussion: https://postgr.es/m/Zmqm9j5EO0I4W8dx@paquier.xyz
This new macro is able to perform a direct lookup from the local cache
of injection points (refreshed each time a point is loaded or run),
without touching the shared memory state of injection points at all.
This works in combination with INJECTION_POINT_LOAD(), and it is better
than INJECTION_POINT() in a critical section due to the fact that it
would avoid all memory allocations should a concurrent detach happen
since a LOAD(), as it retrieves a callback from the backend-private
memory.
The documentation is updated to describe in more details how to use this
new macro with a load. Some tests are added to the module
injection_points based on a new SQL function that acts as a wrapper of
INJECTION_POINT_CACHED().
Based on a suggestion from Heikki Linnakangas.
Author: Heikki Linnakangas, Michael Paquier
Discussion: https://postgr.es/m/58d588d0-e63f-432f-9181-bed29313dece@iki.fi
This can be used to load an injection point and prewarm the
backend-level cache before running it, to avoid issues if the point
cannot be loaded due to restrictions in the code path where it would be
run, like a critical section where no memory allocation can happen
(load_external_function() can do allocations when expanding a library
name).
Tests can use a macro called INJECTION_POINT_LOAD() to load an injection
point. The test module injection_points gains some tests, and a SQL
function able to load an injection point.
Based on a request from Andrey Borodin, who has implemented a test for
multixacts requiring this facility.
Reviewed-by: Andrey Borodin
Discussion: https://postgr.es/m/ZkrBE1e2q2wGvsoN@paquier.xyz
Make the isolation harness recognize injection_points wait events as a
type of blocked state. Test an extant inplace-update bug.
Reviewed by Robert Haas and Michael Paquier.
Discussion: https://postgr.es/m/20240512232923.aa.nmisch@google.com
This commit fixes a race condition between injection point run and
detach, where a point detached by a backend and concurrently running in
a second backend could cause the second backend to do an incorrect
condition check. This issue happens because the second backend
retrieves the callback information in a first step in the shmem hash
table for injection points, and the condition in a second step within
the callback. If the point is detached between these two steps, the
condition would be removed, causing the point to run while it should
not. Storing the condition in the new private_data area introduced in
33181b48fd0e ensures that the condition retrieved is consistent with its
callback.
This commit leads to a lot of simplifications in the module
injection_points, as there is no need to handle the runtime conditions
inside it anymore. Runtime conditions have no more a maximum number.
Per discussion with Noah Misch.
Reviewed-by: Noah Misch
Discussion: https://postgr.es/m/20240509031553.47@rfd.leadboat.com
This commit extends the backend-side infrastructure of injection points
so as it becomes possible to register some input data when attaching a
point. This private data can be registered with the function name and
the library name of the callback when attaching a point, then it is
given as input argument to the callback. This gives the possibility for
modules to pass down custom data at runtime when attaching a point
without managing that internally, in a manner consistent with the
callback entry retrieved from the hash shmem table storing the injection
point data.
InjectionPointAttach() gains two arguments, to be able to define the
private data contents and its size.
A follow-up commit will rely on this infrastructure to close a race
condition with the injection point detach in the module
injection_points.
While on it, this changes InjectionPointDetach() to return a boolean,
returning false if a point cannot be detached. This has been mentioned
by Noah as useful when it comes to implement more complex tests with
concurrent point detach, solid with the automatic detach done for local
points in the test module.
Documentation is adjusted in consequence.
Per discussion with Noah Misch.
Reviewed-by: Noah Misch
Discussion: https://postgr.es/m/20240509031553.47@rfd.leadboat.com
Injection points created under injection_points_set_local() are cleaned
up by a shmem_exit() callback. The spinlock used by the module would
be hold while calling InjectionPointDetach(), which is incorrect as
spinlocks should avoid external calls while hold.
This commit changes the shmem_exit() callback to detach the points in
three steps with the spinlock acquired twice, knowing that the
injection points should be around with the conditions related to them:
- Scans for the points to detach in a first loop, while holding the
spinlock.
- Detach them.
- Remove the registered conditions.
It is still possible for other processes to detach local points
concurrently of the callback. I have wanted to restrict the detach, but
Noah has mentioned that he has in mind some cases that may require this
capability. No tests in the tree based on injection points need that
currently.
Thinko in f587338dec87.
Reported-by: Noah Misch
Reviewed-by: Noah Misch
Discussion: https://postgr.es/m/20240501231214.40@rfd.leadboat.com
The module relies on a shmem exit callback to clean up any injection
points linked to a specific process. One of the tests checks for the
case of an injection point name reused in a second connection where the
first connection should clean it up, but it did not count for the fact
that the shmem exit callback of the first connection may not have run
when the second connection begins its work.
The regress library includes a wait_pid() that can be used for this
purpose, instead of a custom wait logic, so let's rely on it to wait for
the first connection to exit before working with the second connection.
The module gains a REGRESS_OPTS to be able to look at the regress
library's dlpath.
This issue could be reproduced with a hardcoded sleep() in the shmem
exit callback, and the CI has been able to trigger it sporadically.
Oversight in f587338dec87.
Reported-by: Bharath Rupireddy
Reviewed-by: Andrey Borodin
Discussion: https://postgr.es/m/ZhOd3NXAutteokGL@paquier.xyz
This adds a new SQL function injection_points_set_local() that can be
used to force injection points to be run only in the process where they
are attached. This is handy for SQL tests to:
- Detach automatically injection points when the process exits.
- Allow tests with injection points to run concurrently with other test
suites, so as such modules do not have to be marked with
NO_INSTALLCHECK.
Currently, the only condition that can be registered is for a PID.
This could be extended to more kinds later, if required, like database
names/OIDs, roles, or more concepts I did not consider.
Using a single function for SQL scripts is an idea from Heikki
Linnakangas.
Reviewed-by: Andrey Borodin
Discussion: https://postgr.es/m/ZfP7IDs9TvrKe49x@paquier.xyz
The buildfarm script attempts to run all tests marked as
NO_INSTALLCHECK under src/test/modules without paying attention to
whether they are enabled or disabled in the parent Makefile. That
hasn't been a problem so far, because all the tests marked with
NO_INSTALLCHECK ran unconditionally in "make check". But commit
e2e3b8ae9e changed that: the injection fault tests are marked as
NO_INSTALLCHECK, and also depend on --enable-injection-points.
Try to work around that by ensuring that "make check" does nothing in
the those subdirectories. We can hopefully get rid of this hack soon,
after fixing the buildfarm client, or by switching to meson.
Discussion: https://www.postgresql.org/message-id/8e4cf596-dd70-432e-9068-16466ed596ed%40iki.fi
This commit adds two features to the in-core module for injection
points:
- A new callback called "wait" that can be attached to an injection
point to make it wait.
- A new SQL function to update the shared state and broadcast the update
using a condition variable. This function uses an input an injection
point name.
This offers the possibility to stop a process in flight and wake it up
in a controlled manner, which is useful when implementing tests that aim
to trigger scenarios for race conditions (some tests are planned for
integration). The logic uses a set of counters with a condition
variable to monitor and broadcast the changes. Up to 8 waits can be
registered in a single run, which should be plenty enough. Waits can be
monitored in pg_stat_activity, based on the injection point name which
is registered in a custom wait event under the "Extension" category.
The shared memory state used by the module is registered using the DSM
registry, and is optional, so there is no need to load the module with
shared_preload_libraries to be able to use these features.
Author: Michael Paquier
Reviewed-by: Andrey Borodin, Bertrand Drouvot
Discussion: https://postgr.es/m/ZdLuxBk5hGpol91B@paquier.xyz
This provides basic coverage for injection points within a single
process, while providing some callbacks that can be used for other
tests. There are plans to extend this module later with more
advanced capabilities for tests.
Author: Michael Paquier, with comment fixes from Ashutosh Bapat.
Reviewed-by: Ashutosh Bapat, Nathan Bossart, Álvaro Herrera, Dilip
Kumar, Amul Sul, Nazir Bilal Yavuz
Discussion: https://postgr.es/m/ZTiV8tn_MIb_H2rE@paquier.xyz
