[IPython-User] Debug code on ipengine in IDE (Re: Question about schedulers)

[Jon Olav Vik]

Darren Govoni <darren <at> ontrenet.com> writes:

> Incidentally, I discovered that I can execute the ipengine code directly
> in my python IDE and set break points in my user code modules and when I
> execute functions from remote clients/views, it will hit the break
> points and let me debug my code visually (in the running engine). Pretty
> sweet. Though I'd share.

Brilliant! This works in Eclipse PyDev on Windows too. What I did:

1. Create an Eclipse project for the c:\python27\scripts folder.
2. Run "ipcluster start --n=0", e.g. in a command window.
3. In Eclipse, open the code you want to debug and set a breakpoint there.
4. In your "scripts" Eclipse project, open ipengine-script.py and "debug as 
python run".
5. Run some code that uses IPython.parallel.Client().

In the example below,
cell.py is my main script.
It creates a Client() 
which parallelizes cell.py:do(), 
which calls task.py:pace().

The "debug" tab in Eclipse shows an impressive call stack:

scripts ipengine-script.py [Python Run]	
	ipengine-script.py	
		MainThread - pid6940_seq2	
			pace [task.py:26]	
			do [cell.py:54]	
			<module> [<string>:1]	
			apply_request [streamkernel.py:337]	
			dispatch_queue [streamkernel.py:399]	
			dispatcher [streamkernel.py:408]	
			_run_callback [zmqstream.py:365]	
			_handle_recv [zmqstream.py:424]	
			_handle_events [zmqstream.py:391]	
			start [ioloop.py:330]	
			start [ipengineapp.py:316]	
			launch_new_instance [ipengineapp.py:325]	
			<module> [ipengine-script.py:9]	
			run [pydevd.py:1060]	
			<module> [pydevd.py:1346]	
		Thread-4 - pid6940_seq4	
	ipengine-script.py	
metamod cell.py (1) [Python Run]	
	C:\git\metamod\cell.py