Re: Adding facility for injection points (or probe points?) for more advanced tests

On Tue, Jan 2, 2024 at 3:36 PM Ashutosh Bapat
<ashutosh(dot)bapat(dot)oss(at)gmail(dot)com> wrote:

>
> I will look at 0002 next.

One more comment on 0001
InjectionPointAttach() doesn't test whether the given function exists
in the given library. Even if InjectionPointAttach() succeeds,
INJECTION_POINT might throw error because the function doesn't exist.
This can be seen as an unwanted behaviour. I think
InjectionPointAttach() should test whether the function exists and
possibly load it as well by adding it to the local cache.

0002 comments
--- /dev/null
+++ b/src/test/modules/test_injection_points/expected/test_injection_points.out

When built without injection point support, this test fails. We should
add an alternate output file for such a build so that the behaviour
with and without injection point support is tested. Or set up things
such that the test is not run under make check in that directory. I
will prefer the first option.

+
+SELECT test_injection_points_run('TestInjectionError'); -- error
+ERROR: error triggered for injection point TestInjectionError
+-- Re-load and run again.

What's getting Re-loaded here? \c will create a new connection and
thus a new backend. Maybe the comment should say "test in a fresh
backend" or something of that sort?

+
+SELECT test_injection_points_run('TestInjectionError'); -- error
+ERROR: error triggered for injection point TestInjectionError
+-- Remove one entry and check the other one.

Looks confusing to me, we are testing the one removed as well. Am I
missing something?

+(1 row)
+
+-- All entries removed, nothing happens

We aren't removing all entries TestInjectionLog2 is still there. Am I
missing something?

0003 looks mostly OK.

0004 comments

+
+# after recovery, the server will not start, and log PANIC: could not
locate a valid checkpoint record

IIUC the comment describes the behaviour with 7863ee4def65 reverted.
But the test after this comment is written for the behaviour with
7863ee4def65. That's confusing. Is the intent to describe both
behaviours in the comment?

+
+ /* And sleep.. */
+ ConditionVariablePrepareToSleep(&inj_state->wait_point);
+ ConditionVariableSleep(&inj_state->wait_point, test_injection_wait_event);
+ ConditionVariableCancelSleep();

According to the prologue of ConditionVariableSleep(), that function
should be called in a loop checking for the desired condition. All the
callers that I examined follow that pattern. I think we need to follow
that pattern here as well.

Below comment from ConditionVariableTimedSleep() makes me think that
the caller of ConditionVariableSleep() can be woken up even if the
condition variable was not signaled. That's why the while() loop
around ConditionVariableSleep().

* If we're still in the wait list, then the latch must have been set
* by something other than ConditionVariableSignal; though we don't
* guarantee not to return spuriously, we'll avoid this obvious case.
*/.

That's all I have for now.

--
Best Wishes,
Ashutosh Bapat