Is writing a daemon in Python a good idea?

Question

I have to write a daemon program that constantly runs in the background and performs some simple tasks. The logic is not complicated at all, however it has to run for extended periods of time and be stable.

I think C++ would be a good choice for writing this kind of application, however I'm also considering Python since it's easier to write and test something quickly in it.

The problem that I have with Python is that I'm not sure how its runtime environment is going to behave over extended periods of time. Can it eat up more and more memory because of some GC quirks? Can it crash unexpectedly? I've never written daemons in Python before, so if anyone here did, please share your experience. Thanks!

Answer 1

I've written a number of daemons in Python for my last company. The short answer is, it works just fine. As long as the code itself doesn't have some huge memory bomb, I've never seen any gradual degradation or memory hogging. Be mindful of anything in the global or class scopes, because they'll live on, so use del more liberally than you might normally. Otherwise, like I said, no issues I can personally report.

And in case you're wondering, they ran for months and months (let's say 6 months usually) between routine reboots with zero problems.

Answer 2

Yes it can leak. Yes it can crash unexpectedly. Anything can.

I'd say you're far more likely to end up accidentally leaking in an environment with manual memory management (eg C++) than you are with something like Python.

As for crashing unexpectedly, well, chances are an arbitrary lump of Python might be more likely to crash unexpectedly than an arbitrary lump of Java, because the latter benefits from static typing where you can catch a whole load of errors at compile time, that Python with its duck typing and other forms of flexibility.

Realistically, Python sounds a perfectly reasonable choice for what you want to do. Take a look at something like Twisted for a decent engine to build things around, or at least for an idea of structure (your question sounds like some sort of school assignment, so I'm not sure how much freedom of implementation you get)

Answer 3

I've written many things in C/C++ and Perl that are initiated when a LINUX box OS boots, launching them using the rc.d.

Also I've written a couple of java and python scripts that are started the same way I've mentioned above, but I needed a little shell-script (.sh file) to launch them and I used rc.5.

Let me tell you that your concerns about their runtime environments are completely valid, you will have to be careful about wich runlevel you'll use... (only from rc.2 to rc.5, because rc.1 and rc.6 are for the System).

If the runlevel is too low, the python runtime might not be up at the time you are launching your program and it could flop. eg: In a LAMP Server MySQL and Apache are started in rc.3 where the Network is already available.

I think your best shot is to make your script in python and launch it using a .sh file from rc.5.

Good luck!