Re: pgsql: psql: Add test for query canceling

> On 25 Aug 2021, at 07:37, Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr> wrote:
>
>
>> That looks pretty solid to me, and I can confirm that it passes
>> on wrasse's host. The only nit I can find to pick is that this:
>>
>> + usleep(10_000) until -s "$tempdir/psql.pid" or ($count++ > 180 * 100 and die 'pid file did not appear');
>>
>> basically assumes that psql.pid will be written atomically.
>
>> It'd be marginally safer to wait till psql.pid can be seen to
>> contain a newline. I don't think that would be too hard to do,
>> if you put the slurp_file call inside the wait loop and inspect
>> its result.
>
> I finally came around to have a look at the patch.
>
> For the issue raised above, I can see that the file could be created but not yet written, but as the patch waits for the file to be non zero, ISTM that the probability of a torn write of a single integer by echo is so remote that we could let it as that?
>
> Attached a version with the slurping in the loop anyway.

It might be that the risk of a torn write is close to negligible, but that just
means that it’s bound to happen, and pretty soon too =) Checking with slurping
in the loop seems like a good idea to me.

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