Re: pgsql: Add function to pump IPC process until string match

> On 30 Mar 2022, at 00:58, Andres Freund <andres@anarazel.de> wrote:
> On 2022-02-23 13:32:03 +0000, Daniel Gustafsson wrote:

>> Add function to pump IPC process until string match
>>
>> Refactor the recovery tests to not carry a local duplicated copy of
>> the pump_until function which pumps a process until a defined string
>> is seen on a stream. This reduces duplication, and is in preparation
>> for another patch which will also use this functionality.
>
> I'm a bit disappointed by the moved function not having the diagnostic output
> that at least the version in 013_crash_restart.pl had.  How is one supposed to
> figure out what caused a timeout with the new central version?

Thats my bad then.  Since we don't really have diag output in any module I was
going off that "precedent" when moving this over.

> Given that timeouts are the only way tests using pump_until() fail, that's not
> great.

They can also fail on the pumped process crashing/exiting before the timeout
without emitting the expected output.

Would adding back something like the (right now untested) below be what you're
after?  Looking at the perldoc I didn't see any other debugging aids we can
emit other than the stream and type of error.

diff --git a/src/test/perl/PostgreSQL/Test/Utils.pm b/src/test/perl/PostgreSQL/Test/Utils.pm
index 15b314d1f8..693f2f02e5 100644
--- a/src/test/perl/PostgreSQL/Test/Utils.pm
+++ b/src/test/perl/PostgreSQL/Test/Utils.pm
@@ -426,8 +426,16 @@ sub pump_until
     while (1)
     {
         last if $$stream =~ /$until/;
-        return 0 if ($timeout->is_expired);
-        return 0 if (not $proc->pumpable());
+        if ($timeout->is_expired)
+        {
+            diag("pump_until: timeout expired with stream: \"$$stream\"");
+            return 0;
+        }
+        if (not $proc->pumpable())
+        {
+            diag("pump_until: process terminated unexpectedly with stream: \"$$stream\"");
+            return 0
+        }
         $proc->pump();
     }
     return 1;

--
Daniel Gustafsson        https://vmware.com/