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Re: [INTERFACES] Asynchronous connect using libpq

From: eem21(at)cam(dot)ac(dot)uk
To: tgl(at)sss(dot)pgh(dot)pa(dot)us
Cc: pgsql-interfaces(at)postgresql(dot)org
Subject: Re: [INTERFACES] Asynchronous connect using libpq
Date: 1999-07-18 16:02:29
Message-ID: E115tHg-00057Q-00@red.csi.cam.ac.uk (view raw or flat)
Thread:
Lists: pgsql-interfaces
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.


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