poking around a running program

[Paul Rubin]

I have a long-running program that has lots of net connections open on
separate threads. I'm twiddling my thumbs waiting for it to finish
(each run takes maybe an hour) and although I'm logging various info
that I can monitor as the run progresses, it would be cool to be able
to actually poke around the program's data while it's running.

I'm thinking of adding a "console" thread that would basically be a
read-eval-print loop that I could use to inspect data interactively.
Maybe it would just eval stuff or maybe it would use pdb. Of course
it would be a bit dangerous since I could mutate things with it but I
guess it would be enough to just be careful not to do that.

Is this kind of thing common? Has it been done before and are there
some recipes? I did a quick search and didn't find anything obvious.
One thing I'm wondering is how to examine the internal state of
iterators, especially the C implementations from itertools.

More advanced might be some kind of hot-patching scheme (to be able to
change the code without stopping it) but for now I think I'm ok just
restarting the program every so often, modifying the code between runs
based on what happens in a given run.

[Gabriel Genellina]

En Thu, 14 Jun 2007 21:42:50 -0300, Paul Rubin
<"http://phr.cx"@NOSPAM.invalidescribió:

I have a long-running program that has lots of net connections open on
separate threads. I'm twiddling my thumbs waiting for it to finish
(each run takes maybe an hour) and although I'm logging various info
that I can monitor as the run progresses, it would be cool to be able
to actually poke around the program's data while it's running.

I'm thinking of adding a "console" thread that would basically be a
read-eval-print loop that I could use to inspect data interactively.
Maybe it would just eval stuff or maybe it would use pdb. Of course
it would be a bit dangerous since I could mutate things with it but I
guess it would be enough to just be careful not to do that.

Is this kind of thing common? Has it been done before and are there
some recipes? I did a quick search and didn't find anything obvious.
One thing I'm wondering is how to examine the internal state of
iterators, especially the C implementations from itertools.

I don't know how common it is, but for instance, Zope has a remote console
like this.
The code module may be useful.

More advanced might be some kind of hot-patching scheme (to be able to
change the code without stopping it) but for now I think I'm ok just
restarting the program every so often, modifying the code between runs
based on what happens in a given run.

That may be hard to do. For global functions, reload() may help, but if
you have many created instances, modifying and reloading the module that
contains the class definition won't automatically alter the existing
instances.

--
Gabriel Genellina

[Bjoern Schliessmann]

Paul Rubin wrote:

Is this kind of thing common? Has it been done before and are
there some recipes?

The Twisted framework offers an interactive Python shell inside the
application (Twisted manhole).

Regards,
Björn

--
BOFH excuse #249:

Unfortunately we have run out of bits/bytes/whatever. Don't worry,
the next supply will be coming next week.