Re: Question!

[Jorge Opaso Pazos <jopaso@trofeospazos.com>]

Mariano Moreyra wrote:
> The problem is that the child is waiting for the script to finish (the one
> that start mysqld) so the child sends a response to the client telling him
> that the script finished ok (or not).
> So, if I close the socket, the child can't send the response.
> I tried to find a solution to this situation, but the client needs to know
> the exit status of the script.
> The parent process has his own socket listening for incoming connections and
> forks the childs. These childs accepts the connections on his own sockets,
> so  childs doesn't inherit the parent's socket.
> It's ok to do that?? Or I'm doing something wrong with the sockets??
> Thanks a lot to all of you for your answers!!
> 
> -----Mensaje original-----
> De: linux-c-programming-owner@vger.kernel.org
> [mailto:linux-c-programming-owner@vger.kernel.org]En nombre de Luciano
> Miguel Ferreira Rocha
> Enviado el: Jueves, 04 de Septiembre de 2003 14:54
> Para: Jorge Opaso Pazos
> CC: linux-c-programming@vger.kernel.org
> Asunto: Re: Question!
> 
> 
> On Thu, Sep 04, 2003 at 12:04:43PM -0400, Jorge Opaso Pazos wrote:
> 
>>Mariano Moreyra wrote:
>>
>>>Hola!
>>>Te mando la seccion del programa que ejecuta el script en si.
>>>
>>>Este proceso lo unico que espera del script es que el mismo conteste con
> 
> un
> 
>>>"-" si hubo algun error o con un "+" si salio todo bien
>>>
>>>----------------------------------------------------------
>>>   if(err==0) {
>>>     pipe_in = popen(shell_cmd,"r");
>>>     fgets(response,5,pipe_in);
>>>
>>>     if(response[0]=='-') {
>>>       err=1;
>>>     } else if(response[0]=='+') {
>>>       err=0;
>>>     };
>>>     while(fgets(response,5,pipe_in)) {
>>>     };
>>>     pclose(pipe_in);
>>>   };
>>>-----------------------------------------------------------
>>>
>>>El script lo unico que hace es copiar algunos archivos y luego leventar
> 
> el
> 
>>>MySQL con el
>>>safe_mysqld
>>>
>>>Espero que esto sirva! Muchas gracias!!
>>>Saludos!!
>>>
>>>
>>>
>>>-----Mensaje original-----
>>>De: linux-c-programming-owner@vger.kernel.org
>>>[mailto:linux-c-programming-owner@vger.kernel.org]En nombre de Jorge
>>>Opaso Pazos
>>>Enviado el: Miércoles, 03 de Septiembre de 2003 18:09
>>>Para: linux-c-programming@vger.kernel.org
>>>Asunto: Re: Question!
>>>
>>>
>>>Mariano Moreyra wrote:
>>>
>>>
>>>>Hi!!
>>>>First...I'd like to know if there is any kind of digest on this list to
>>>
>>>see
>>>
>>>
>>>>old submited messages.
>>>>
>>>>Now...I have a little problem.
>>>>I have a process that is listening for incoming connections on a socket.
>>>>That process waits for a command and then
>>>>forks a child to run a bash script.
>>>>The problems is:
>>>>	- When the bash script runs the safe_mysql script to run MySql
>>>>	engine,
>>>
>>>it's
>>>
>>>
>>>>like the child process never ends.
>>>>	  And because of that, the parent can't close the connection with the
>>>>client socket.
>>>>	- But if the bash script doesn't run the safe_mysql script...the
>>>>	child
>>>>process dies successfully and everything end
>>>>	  Ok
>>>>
>>>>Sorry about my english, but I hope that I made my self clear....
>>>>Bye!
>>>>
>>>>-
>>>>To unsubscribe from this list: send the line "unsubscribe
>>>
>>>linux-c-programming" in
>>>
>>>
>>>>the body of a message to majordomo@vger.kernel.org
>>>>More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>>>
>>>
>>>
>>>envíame el script.
>>>
>>>-
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>>>
>>
>>English: I suspect that the problem is that safe_mysqld don't return
>>until mysqld ends.
>>Try to execute safe_mysqld in background in the shellscript:
>>
>>	if ! pgrep mysqld
>>	then
>>		/usr/bin/safe_mysqld &
>>	fi
> 
> As the socket is inherited, the remote client will never exit.
> If the popen is after a fork(), then it doesn't matter if safe_mysql doesn't
> end, as the parent wouldn't be waiting on it.
> 
> My bet is in the socket not being closed, either in the parent, child, or
> both, or before the execution of safe_mysql. (If mysqld inherits the socket,
> then the connection won't close until mysqld does.)
> 
> 
>>Castellano: El problema debe ser que no termina safe_mydqld hasta que no
>>termina mysqld. Se podría solucionar llamando a safe_mysqld en
>>"background" de la forma anterior.
> 
> 
> Portugues: AH! that would be something :)
> 
> Regards,
> Luciano Rocha
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> 

Hi Mariano, hi Luciano.

When we make a concurrent server (a server that spawn a child process 
when accept return) always the parent have to close de socket returned 
by accept and the child have to close the socket that the server use to 
call accept (server socket).
I you have to inform the client about the exit status of the script, the 
better way (I think) is to execute the script in the child with 
system(3), because you need the exit status of the script, not the 
output. About the safe_mysqld, you must send it to bg.

Luciano, I've never heard the lsof command, thanks.

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