Removing "raise" as well as print... and a demo of running a background reposync with proper task-specific logging

[Michael DeHaan]

I've added a function "utils.die(logger, msg)" that I'm going to be 
moving things to instead of raise while I'm in the process of removing 
print statements.

def die(logger, msg):

    # log the exception once in the per-task log or the main
    # log if this is not a background op.
    try:
       raise CX(msg)
    except:
       if logger is not None:
           log_exc(logger)
       else:
           log_exc(main_logger)

    # now re-raise it so the error can fail the operation
    raise CX(msg)


The reason for this is that different task logs need to log their 
exceptions (if any) in the individual task files as opposed to in the 
main log, and there is not any global
try/catch logic in the actions or the API... this is normally done in 
the web application or CLI.

This is not totally refined yet (just added for reposync so far), though 
the intent is that the full traceback will be in the log file for any 
utils.die() calls and that these will also
show up as the nicely formatted error messages we have today (no 
traceback) in the web app or CLI, with a link to the logs, where relevant.

This may also eventually mean there is more logic in the die call later, 
TBD.

It's a little weird, but it's all in the course of implementing our 
system of being able to run things in the background or the foreground 
and have them log (conditionally) to the correct place.

For example, added distributions should go to the main log, but import 
is a background task, so added distributions added during the import go 
to the main log.

Perhaps this can be a little cleaner but it is a start.

Next week, we'll work on removing the remaining print calls throughout 
the actions and also cleaning up the exception handling.  

For trying this all out, download a new checkout of cobbler-devel, run 
"make webtest" to make sure the new daemon is running, and run the test 
program:

#!/usr/bin/python

import xmlrpclib
import time

s = xmlrpclib.Server("http://127.0.0.1/cobbler_api")
token = s.login("testing","testing")

# task1 = s.background_sync(token)
task2 = s.background_reposync(["r1","r2"], 3, token)
# new function names are subject to change until released

#print s.get_task_status(task1)
while True:
    print s.get_task_status(task2)
    time.sleep(1)

While that is running, issue the following 3 times:

sudo pkill reposync
sudo pkill reposync
sudo pkill reposync

You should see the task status move to "failed"

If you look in the logfile /var/log/cobbler/tasks/0.log, you should see 
the exception.

(In the above example, I've briefly commented out the code to also try a 
background sync, which ends up being so instanteous in my environment 
there is little point in backgrounding it, but it is true that folks 
could have post-sync triggers installed that fire off other actions).

Obviously in addition to all of this cleanup and making the CLI be 
remoted we also have to make tasks show up in the web app so you can see 
the results of the task that you kick off, as well as list tasks (and if 
there's a task queue, which there currently is not one implemented/needed).

--Michael