Re: [INTERFACES] Asynchronous connect using libpq

On 18 Jul, Tom Lane wrote:
> eem21(at)cam(dot)ac(dot)uk writes:
>> I realised that some time after I sent my first message, and have been
>> thinking about it since. The delay for gethostbyname is not
>> acceptable, and we are going to have to get around that problem
>> elsewhere in the application anyway. Therefore, I was thinking that I
>> could arrange to pass an IP address into libpq.
>
> A dotted-decimal address, you mean? Yeah, that sounds like it should
> work.

Or a struct in_addr *. I'll have to see how IPv6 addresses are being
shoehorned into the socket schemes. Perhaps we could support them too.

>> With regards to the connect() problem, I was hoping that by setting the
>> socket to non-blocking mode before connecting (exactly as it is
>> currently done after the connect call) I could solve that problem.
>
> By golly, there is something about non-blocking connect in the man page:
>
> If the socket is of type SOCK_STREAM, connect() attempts to contact
> the remote host in order to make a connection between the remote
> socket (peer) and the local socket specified by s. The call normally
> blocks until the connection completes. If non-blocking mode has been
> enabled using the O_NONBLOCK or O_NDELAY fcntl() flags or the FIOSNBIO
> ioctl() request and the connection cannot be completed immediately,
> connect() returns an error as described below. In these cases,
> select() can be used on this socket to determine when the connection
> has completed by selecting it for writing.
>
> Maybe you can make this work after all, with the limitation that the
> user must supply a dotted-decimal IP address (or use a Unix-domain
> connection) if he doesn't want to risk DNS lookup delays.
>
> Good luck!

Thanks!

Ewan.