sockets,threads and interupts

[loial]

I have threaded python script that uses sockets to monitor network ports.

I want to ensure that the socket is closed cleanly in all circumstances. This includes if the script is killed or interupted in some other way.

As I understand it signal only works in the main thread, so how can I trap interupts in my threaded class and always ensure I close the socket? Using KeyboardInterupt does not seem to work.

[MRAB]

You could wrap it in try...finally. The 'finally' clause is guaranteed
to be run, so you can close the sockets there.

However, if the script is just killed, then it won't get the chance to
tidy up.

[Grant Edwards]

That depends on the signal used to "kill" the thread.

You can catch SIGTERM and SIGINT and clean up before exiting.

You can't catch SIGKILL, but sending a SIGKILL isn't considered polite
unless you've already tried SIGTERM/SIGINT and it didn't work.

--
Grant Edwards grant.b.edwards Yow! Are we on STRIKE yet?
at
gmail.com

[Ramchandra Apte]

We could just use a "with" statement. Neater, easier.

[Dieter Maurer]

loial <jldun...@gmail.com> writes:

> I have threaded python script that uses sockets to monitor network ports.
>
> I want to ensure that the socket is closed cleanly in all circumstances. This includes if the script is killed or interupted in some other way.

The operating system should close all sockets automatically when
the process dies. Thus, if closing alone is sufficient...

[Ramchandra Apte]

At least on Linux, if you kill a process using sockets, it takes about 10 seconds for socket to be closed. A program should try to close all resources. OS'es may take a long time to close a unclosed socket automatically.

[Ramchandra Apte]

On Wednesday, 5 September 2012 11:26:16 UTC+5:30, Dieter Maurer wrote:

[Chris Angelico]

On Wed, Sep 5, 2012 at 10:54 PM, Ramchandra Apte <manian...@gmail.com> wrote:
> At least on Linux, if you kill a process using sockets, it takes about 10 seconds for socket to be closed. A program should try to close all resources. OS'es may take a long time to close a unclosed socket automatically.

Err, that's not my experience. When a process terminates, its
resources are released promptly.

ChrisA

[Ramchandra Apte]

It is not guaranteed so a program shouldn't presume.
>
>
>
> ChrisA

[Ramchandra Apte]

On Wednesday, 5 September 2012 18:34:32 UTC+5:30, Chris Angelico wrote:

[Ramchandra Apte]

oops forgot my signature
---
Bragging rights (I belong an exclusive community of banned people): got banned on SO and #python-offtopic
Projects:http://code.google.com/p/py2c/ and http://code.google.com/p/uniqos (name may be changed to PyOS)

[Ramchandra Apte]

On Wednesday, 5 September 2012 21:29:12 UTC+5:30, Ramchandra Apte wrote:

[Bryan]

loial wrote:
> I have threaded python script that uses sockets to monitor network ports.
>
> I want to ensure that the socket is closed cleanly in all circumstances. This includes if the script is killed or interupted in some other way.
>
> As I understand it signal only works in the main thread, so how can I trap interupts in my threaded class and always ensure I close the socket?

You may have various threads waiting in blocking calls, and I don't
think there's a good way to alert them. Closing sockets that other
threads may be waiting on is "probably unwise" according to Linux man
page on close(2).

Do you really need to worry about it? If your process is being
forcibly terminated you probably cannot do anything better than the OS
will do by default.

-Bryan