Running webapp2 outside of appengine, how to run it as a service/deamon?

I just finished my app and would like to deploy it. But how to run my app as a service/deamon?

A google search showed some different approches using some python开发者_如何学运维 libraries, twisted and Can I run a Python script as a service?. But can't figure out how to do it.

Any one done this? Is there a best-practice approach?

..fredrik

As you want your application to run standalone (if i understood correctly), you could handle this like with any other (non-web) application.

If you just want your program to run in the background, you could read this receipe that explains how to create a daemon application and has a nice discussion about this topic (in the comments).

On the other hand, if you want to make a "system daemon" with your app (which starts at every system's startup), i'd go with a shell script. To see how to create startup scripts for your system, you could get inspiration from the other startup scripts on your machine. A solution would be to run your program in the background with python my_app.py & (from the startup script), and then use the $! variable to get the process' pid and store it to a file, this way you would also be able to stop your process by reading the "pid file" and use the kill command (sending a SIGINT to your process will provoke a KeyboardInterrupt exception to be raised in your application).

EDIT:

In your question comments, you say using python main.py & would be unsafe as the application wouldn't restart if it failed/crashed, but that's the same with any other daemon on your system (for example, if Apache crashed, it would'nt restart by itself). If you want to restart your application if it crashes, you would have to write a 2nd daemon, that would check at regular intervals if your application is still running, and restart it if needed.

About the logging thing, you can either make your application output to stdout/stderr and redirect it from the startup script (python main.py &> /path/to/app.log &) or handle logging from your application, using the logging module.

Alternatively, you can easily run and control the deamonized process with supervisord and log its stdout/stderr output too.

• http://supervisord.org/
• http://packages.debian.org/supervisor

Demonizing a python script is actually demonizing python.

If you are the root, consider using GNU screen to do that job. Screen itself will handle the terminal control which is usually the most complicated task regarding to build a daemon process.

Start a screen, run your program, detach, then logout if you wish, and it will leave a daemon-like process behind. This approach is effective especially when your program is under construction, not very stable, or dumping many quickly-written messages for debugging.

Still there are some things to be noted in daemonizing a program, like change the working directory to / and close descriptors not in use in case you have to unmount filesystem, or reprogram the signal handles, ... etc. However, most conditions are satisfied if you daemonize a process from init or a clean login session; just remember to change directory to "/", usually enough.

But using screen doesn't help to survive a crash, crashes are always what programmers have to deal with.