pg_recvlogical, stdout and SIGHUP

On 2014-05-13 16:31:25 +0300, Heikki Linnakangas wrote:

pg_recvlogical re-opens the output file on SIGHUP. If the output goes to
stdout, it will close stdout on SIGHUP. That's a bug, isn't it?

Yes. An annoying one at that because it'll mean a a new connection will
use that fd and we'll start writing stdout stuff to it...

Another thing I noticed is that if when the output goes to a file, the file
isn't re-opened immediately on SIGHUP. Only after receiving some data from
the server. I believe that's also not intentional.

Hm. I can't really get excited about that one. Not doing that seems to
complicate matters unneccessarily. What's the problem here?

Greetings,

Andres Freund

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On 05/13/2014 04:35 PM, Andres Freund wrote:

On 2014-05-13 16:31:25 +0300, Heikki Linnakangas wrote:

Another thing I noticed is that if when the output goes to a file, the file
isn't re-opened immediately on SIGHUP. Only after receiving some data from
the server. I believe that's also not intentional.

Hm. I can't really get excited about that one. Not doing that seems to
complicate matters unneccessarily. What's the problem here?

Not sure if it matters in any real-world scenario, but I found it pretty
surprising while playing with it. It should be trivial to fix; ISTM the
problem is that there is a "continue" in the loop when select() is
interrupted by signal, but the re-opening is done after the select() in
the loop. I think all you need to do is move the check for output_reopen
to the beginning of the loop.

- Heikki

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On 2014-05-13 17:43:47 +0300, Heikki Linnakangas wrote:

On 05/13/2014 04:35 PM, Andres Freund wrote:

On 2014-05-13 16:31:25 +0300, Heikki Linnakangas wrote:

Another thing I noticed is that if when the output goes to a file, the file
isn't re-opened immediately on SIGHUP. Only after receiving some data from
the server. I believe that's also not intentional.

Hm. I can't really get excited about that one. Not doing that seems to
complicate matters unneccessarily. What's the problem here?

Not sure if it matters in any real-world scenario, but I found it pretty
surprising while playing with it. It should be trivial to fix; ISTM the
problem is that there is a "continue" in the loop when select() is
interrupted by signal, but the re-opening is done after the select() in the
loop. I think all you need to do is move the check for output_reopen to the
beginning of the loop.

Thanks for fixing and sorry for being slow :(.

Any reason you didn't also move the opening of the output file up? It
seems a bit odd to not have an output file existing every now and
then...

Greetings,

Andres Freund

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PostgreSQL Development, 24x7 Support, Training & Services

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On 05/15/2014 07:59 PM, Andres Freund wrote:

On 2014-05-13 17:43:47 +0300, Heikki Linnakangas wrote:

On 05/13/2014 04:35 PM, Andres Freund wrote:

On 2014-05-13 16:31:25 +0300, Heikki Linnakangas wrote:

Another thing I noticed is that if when the output goes to a file, the file
isn't re-opened immediately on SIGHUP. Only after receiving some data from
the server. I believe that's also not intentional.

Hm. I can't really get excited about that one. Not doing that seems to
complicate matters unneccessarily. What's the problem here?

Not sure if it matters in any real-world scenario, but I found it pretty
surprising while playing with it. It should be trivial to fix; ISTM the
problem is that there is a "continue" in the loop when select() is
interrupted by signal, but the re-opening is done after the select() in the
loop. I think all you need to do is move the check for output_reopen to the
beginning of the loop.

Thanks for fixing and sorry for being slow :(.

Any reason you didn't also move the opening of the output file up? It
seems a bit odd to not have an output file existing every now and
then...

No particular reason. But that would actually be a great idea, because
currently you won't get any error you give pg_recvlogical an invalid
path, until it receives the first piece of data from the server and
tries to write it to the file. I'll go and do that.

- Heikki

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