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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.

On 04/09/2012 16:26, 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? Using KeyboardInterupt does not seem to work.
>
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.

On 2012-09-04, MRAB <> wrote:
> On 04/09/2012 16:26, 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? Using KeyboardInterupt does not seem to work.
>>
> 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.

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

On Tuesday, 4 September 2012 23:41:13 UTC+5:30, Grant Edwards wrote:
> On 2012-09-04, MRAB <> wrote:
>
> > On 04/09/2012 16:26, 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? Using KeyboardInterupt does not seem to work.
>
> >>
>
> > 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.
>
>
>
> 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

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

loial <> 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...

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

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.

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

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.

On Wed, Sep 5, 2012 at 10:54 PM, Ramchandra Apte <> 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

On Wednesday, 5 September 2012 18:34:32 UTC+5:30, Chris Angelico wrote:
> On Wed, Sep 5, 2012 at 10:54 PM, Ramchandra Apte <> 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.

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

On Wednesday, 5 September 2012 18:34:32 UTC+5:30, Chris Angelico wrote:
> On Wed, Sep 5, 2012 at 10:54 PM, Ramchandra Apte <> 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.

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