Writing a simple linux daemon type thing...

[Radovan Garabik]

Jones <jones at jones.jones> wrote:
 : Hi everyone,
 : I hope this is a simple question for you guys.  I'm new to Python and Linux.
 : I'm wondering if Python (and this group) can help me.
 : I want a program to always be running in the background that, connects to
 : PostgreSQL every few seconds, queries a table, and for each record it finds,
 : shells out to the system to execute program.

 : My research indicates that "nohup" might do the trick?  So would it be as
 : simple as writing the program in Python and then puting something like
 : "nohup python myprog" in the Linux startup sequence (wherever that may be)?

yes
(python myprog &
 would be probably better)

 : That's my primary goal.  Now... assuming I get past that part, I may want to
 : take it a few steps further later on.  I'd be happy if you guys could take a
 : stab at telling me if these are possible and any tips too...
 : a) Make it multi-threaded...   As I said before, the number of times it
 : executes the external program equals the number of records it finds in the
 : table.  It would be nice if I could execute the program multiple times
 : concurrently in a *controlled* manner (depending on my system resources)
 : instead of having to wait for each one to be done before starting another
 : one.

there is no need for it to be multithreaded. Just use
os.system("program.py &")
and the program will be executed in the background
 
 : b) Make it fail-safe.  I would like to figure out how I could re-launch the
 : program if it was to crash.

look for daemontools at http://cr.yp.to

-- 
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| Radovan Garabik  http://melkor.dnp.fmph.uniba.sk/~garabik |
| __..--^^^--..__         garabik @ fmph . uniba . sk       |
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