Re: stray SIGALRM

Richard Poole <richard(at)2ndQuadrant(dot)com> writes:
> In 9.3beta1, a backend will receive a SIGALRM after authentication_timeout
> seconds, even if authentication has been successful. Most of the time
> this doesn't hurt anyone, but there are cases, such as when the backend
> is doing the open() of a backend copy, when it breaks things and results
> in an error getting reported to the client. In particular, if you're doing
> a copy from a FIFO, it is normal for open() to block until the process at
> the other end has data ready, so you're very likely to have it interrupted
> by the SIGALRM and fail.

> To see the SIGALRM just run psql then determine your backend's pid,
> attach an strace to it, and wait 60 seconds, or whatever you've got
> authentication_timeout set to.

> This behaviour appears in 6ac7facdd3990baf47efc124e9d7229422a06452 as a
> side-effect of speeding things up by getting rid of setitimer() calls;
> it's not obvious what's a good way to fix it without losing the benefits
> of that commit.

Ugh. It doesn't sound very practical to try to guarantee that every
single kernel call in the backend is set up to recover from EINTR,
even though ideally they should all be able to cope. Maybe we have to
revert those signal-handling changes.

regards, tom lane