Re: [HACKERS] jacana hung after failing to acquire random number

On 12/12/2016 05:58 AM, Michael Paquier wrote:
> On Sun, Dec 11, 2016 at 9:06 AM, Andrew Dunstan <andrew@dunslane.net> wrote:
>>
>> jascana (mingw, 64 bit compiler, no openssl) is currently hung on "make
>> check". After starting the autovacuum launcher there are 120 messages on its
>> log about "Could not acquire random number". Then nothing.
>>
>>
>> So I suspect the problem here is commit
>> fe0a0b5993dfe24e4b3bcf52fa64ff41a444b8f1, although I haven't looked in
>> detail.
>>
>>
>> Shouldn't we want the postmaster to shut down if it's not going to go
>> further? Note that frogmouth, also mingw, which builds with openssl, doesn't
>> have this issue.
>
> Did you unlock it in some way at the end? Here is the shape of the
> report for others:
> http://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=jacana&dt=2016-12-10%2022%3A00%3A15
> And here is of course the interesting bit:
> 2016-12-10 17:25:38.822 EST [584c80e2.ddc:2] LOG:  could not acquire
> random number
> 2016-12-10 17:25:39.869 EST [584c80e2.ddc:3] LOG:  could not acquire
> random number
> 2016-12-10 17:25:40.916 EST [584c80e2.ddc:4] LOG:  could not acquire
> random number
>
> I am not seeing any problems with MSVC without openssl, so that's a
> problem proper to MinGW. I am getting to wonder if it is actually a
> good idea to cache the crypt context and then re-use it. Using a new
> context all the time is definitely not performance-wise though.

Actually, looking at the config.log on jacana, it's trying to use 
/dev/urandom:

configure:15028: checking for /dev/urandom
configure:15041: result: yes
configure:15054: checking which random number source to use
configure:15073: result: /dev/urandom

And looking closer at configure.in, I can see why:
  elif test "$PORTNAME" = x"win32" ; then    USE_WIN32_RANDOM=1

That test is broken. It looks like the x"$VAR" = x"constant" idiom, but 
the left side of the comparison doesn't have the 'x'. Oops.

Fixed that, let's see if it made jacana happy again.

This makes me wonder if we should work a bit harder to get a good error 
message, if acquiring a random number fails for any reason. This needs 
to work in the frontend as well backend, but we could still have an 
elog(LOG, ...) there, inside an #ifndef FRONTEND block.

- Heikki