Re: mysterious "can't connect" error message in our logs(2)

Jigal van Hemert wrote:
> The continuing saga:
> 
> 
>>    Can't connect to MySQL server on '192.168.13.205' (4)
> 
> Our sysadmin has been searching in the sources of the MySQL client and came
> up with this:
> 
> The errormessage (4) is probably (only place where this error could be
> found) raised by this fragment in libmysql.c:
> 
> if ((sock = (my_socket) socket(AF_INET,SOCK_STREAM,0)) == SOCKET_ERROR)
> {
>   net->last_errno=CR_IPSOCK_ERROR;
>   sprintf(net->last_error,ER(net->last_errno),socket_errno);
>   goto error;
> }
> 
> According to:
> http://www-users.cs.umn.edu/~bentlema/unix/syscalls_and_ipc.html
> this is what happens:
> 
> 1) The MySQL client tries to create a new socket.
> 2) At that moment the thread is interupted by a signal. Control is passed to
> the signal handler.
> 3) After the signal handler has done his work, control goes back to the
> original thread. The socket() function notices that it was interupted and
> returns the error-code.
> 
> If you look at the sample code in section 8.1 of the url above
> 
>           for (;;) {
>                rmask = mask;
>                nfound = select(FD_SETSIZE, &rmask, (fd_set *)0, (fd_set *)0,
> &timeout);
>                if (nfound < 0) {
>                     if (errno == EINTR) {
>                          printf("interrupted system call\n");
>                          continue;
>                     }
>                     /* something is very wrong! */
>                     perror("select");
>                     exit(1);
>                }
> (...)
> 
> The client should try again if the EINTR error was returned.
> 
> Did we do something wrong in the configuration of the server or is this a
> tiny bug?
> 
> Regards, Jigal.

It's a bug. I would recommend to patch libmysql.c for now until MySQL developers 
fix it.

-- 
Sasha Pachev
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