Application monitor

[dcrespo]

Hi to all,

I'd like to have an app monitor that gets rid of another app, in the
way that if it closes unspectedly, the app monitor just wake it up one
more time, and viceversa.

I mean:

Main application starts
This one starts the App Monitor of itself. (This means that if Main
Application closes, the App Monitor restart it)

And viceversa means that if App Monitor closes, the Main application
restart it.

How can I accomplish this?

I've been thinking in wx.SingleInstan ceChecker (from wxPython GUI
library). If it doesn't exist, then call os.system(<prog ram_name>). But
I don't know if there's a better way.

Thanks

Daniel

[Mike Meyer]

Re: Application monitor

"dcrespo" <dcrespo@gmail. com> writes:[color=blue]
> Main application starts
> This one starts the App Monitor of itself. (This means that if Main
> Application closes, the App Monitor restart it)
>
> And viceversa means that if App Monitor closes, the Main application
> restart it.
>
> How can I accomplish this?
>
> I've been thinking in wx.SingleInstan ceChecker (from wxPython GUI
> library). If it doesn't exist, then call os.system(<prog ram_name>). But
> I don't know if there's a better way.[/color]

"Better" depends on what your requirements are. Personally, I use init
as an app monitor. It doesn't need monitoring - if it's dead, your
Unix has a lot worse problems than one application being down.

<mike
--
Mike Meyer <mwm@mired.or g> http://www.mired.org/home/mwm/
Independent WWW/Perforce/FreeBSD/Unix consultant, email for more information.

[dcrespo]

Re: Application monitor

> Personally, I use init[color=blue]
> as an app monitor. It doesn't need monitoring[/color]

What's "init"? Sorry about my ignorance.

[Mike Meyer]

Re: Application monitor

"dcrespo" <dcrespo@gmail. com> writes:[color=blue][color=green]
>> Personally, I use init as an app monitor. It doesn't need monitoring[/color]
> What's "init"? Sorry about my ignorance.[/color]

init is the first Unix process, and all other processes are descended
from it. It is the alpha and the omega of Unix processes. Uh, wait a
second - I'm having biblical flashes here. Let's try again:

init is the first process started when a Unix system boots, and is
hand crafted by the boot process. Every other process on the system is
started by a fork (or a variant) system call, and are descendants of
init. Part of it's job is starting the various server processes on the
system that are appropriate for the system state. It notices when they
exit, and restarts them. On timesharing systems, it will start a login
process on every terminal, which would then exec it's way into a user
shell, which would exit - which init would notice, and launch another
login on that terminal. If init is dead, your Unix system is in a bad
way.

You can use this on modern Unix systems. You add an entry to init's
config file (/etc/inittab on SysV-like systems, and /etc/ttys on
BSD-derived systems), and init will launch a process for that
entry. If the process ever exits, init will launch it again.

For instance, I launch an ssh client to keep a couple of TCP tunnels
open to my ISPs server so I can access services that aren't available
from my current location. I run that via init. No need to worry about
hardening the ssh client, or writing a wrapper around it, or anny such
thing. init deals with all of that for me.

<mike
--
Mike Meyer <mwm@mired.or g> http://www.mired.org/home/mwm/
Independent WWW/Perforce/FreeBSD/Unix consultant, email for more information.

[Magnus Lycka]

Re: Application monitor

dcrespo wrote:[color=blue]
> Hi to all,
>
> I'd like to have an app monitor that gets rid of another app, in the
> way that if it closes unspectedly, the app monitor just wake it up one
> more time, and viceversa.[/color]

Twisted contains such a thing. I think it's called twisted.runner,
and no, it's not just for keeping Twisted processes running.

[Daniel Crespo]

Re: Application monitor

Many thanks for your answers.

Respect Init, I need a cross platform solution. Most of times my system
will run in Win98 and XP (more on XP than 98)

Respect Twisted... Mmm... I already started with another networking
library (TCPServer and SimpleXMLRPCSer ver), and I wouldn't like to mix
things because I don't know so much about those libraries. I know that
Twisted can do what I already have. But replacing it can be a hard
task. So I would like to have a function like FindPID(exename ) --> PID,
or something more generic that could tell me the PID of a running
program, and kill him in a certain moment.

Daniel

[Magnus Lycka]

Re: Application monitor

Daniel Crespo wrote:[color=blue]
> Respect Twisted... Mmm... I already started with another networking
> library (TCPServer and SimpleXMLRPCSer ver), and I wouldn't like to mix
> things because I don't know so much about those libraries. I know that
> Twisted can do what I already have. But replacing it can be a hard
> task. So I would like to have a function like FindPID(exename ) --> PID,
> or something more generic that could tell me the PID of a running
> program, and kill him in a certain moment.[/color]

You *could* use twisted.runner for process control even if you
don't use twisted for your networking code. It does seem like
a funny thing to do, but there's nothing stopping you from doing
that. The example code in twisted.runner starts up a few shell
scripts that die on their own accord, and make sure they get
restarted, so it doesn't rely on twisted being used in the
processes it controls.

[Daniel Crespo]

Re: Application monitor

Magnus Lycka wrote:[color=blue]
> You *could* use twisted.runner for process control even if you
> don't use twisted for your networking code. It does seem like
> a funny thing to do, but there's nothing stopping you from doing
> that. The example code in twisted.runner starts up a few shell
> scripts that die on their own accord, and make sure they get
> restarted, so it doesn't rely on twisted being used in the
> processes it controls.[/color]

Ok. I'll take a look. Thank you very much! :)

Daniel