Hello:
Please refer to the following script:
import sys
import twisted.internet.defer
import twisted.internet.reactor
import twisted.python.log
print "Twisted version", twisted.version
print "Python version", sys.version
class ExceptionToRaise(Exception):
pass
exception_to_raise = ExceptionToRaise()
@twisted.internet.defer.inlineCallbacks
def icb_error_maker():
"""
Raises an exception implemented as an inline inlineCallbacks
"""
raise exception_to_raise
def pod_error_maker():
"""
Raises an exception implemented as a plain old deferred
"""
deferred = twisted.internet.defer.Deferred()
deferred.errback(exception_to_raise)
return deferred
#ERROR_MAKER_TO_USE = icb_error_maker
ERROR_MAKER_TO_USE = pod_error_maker
@twisted.internet.defer.inlineCallbacks
def intermediate_function3():
print 'intermediate_function3 1'
try:
yield ERROR_MAKER_TO_USE()
except BaseException as exception:
print 'intermediate_function3 exception', repr(exception)
raise
print 'intermediate_function3 2'
@twisted.internet.defer.inlineCallbacks
def intermediate_function2():
print 'intermediate_function2 1'
try:
yield intermediate_function3()
except BaseException as exception:
print 'intermediate_function2 exception', repr(exception)
raise
print 'intermediate_function2 2'
@twisted.internet.defer.inlineCallbacks
def intermediate_function1():
print 'intermediate_function1 1'
try:
yield intermediate_function2()
except BaseException as exception:
print 'intermediate_function1 exception', repr(exception)
raise
print 'intermediate_function1 2'
def run():
d = intermediate_function1()
d.addErrback(twisted.python.log.err)
d.addBoth(lambda n: twisted.internet.reactor.stop())
twisted.internet.reactor.callWhenRunning(run)
twisted.internet.reactor.run()
When ERROR_MAKER_TO_USE = icb_error_maker The output is as follows:
Twisted version [twisted, version 13.2.0]
Python version 2.7.3 (default, Feb 27 2014, 20:00:17)
[GCC 4.6.3]
intermediate_function1 1
intermediate_function2 1
intermediate_function3 1
intermediate_function3 exception ExceptionToRaise()
intermediate_function2 exception ExceptionToRaise()
intermediate_function1 exception ExceptionToRaise()
Unhandled Error
Traceback (most recent call last):
File
"/home/daveb/bzr_repo/player_rm2/test2/local/lib/python2.7/site-packages/twisted/internet/defer.py",
line 1237, in unwindGenerator
return _inlineCallbacks(None, gen, Deferred())
File
"/home/daveb/bzr_repo/player_rm2/test2/local/lib/python2.7/site-packages/twisted/internet/defer.py",
line 1099, in _inlineCallbacks
result = g.send(result)
File "icb_error_test1.py", line 52, in intermediate_function2
yield intermediate_function3()
File
"/home/daveb/bzr_repo/player_rm2/test2/local/lib/python2.7/site-packages/twisted/internet/defer.py",
line 1237, in unwindGenerator
return _inlineCallbacks(None, gen, Deferred())
--- <exception caught here> ---
File
"/home/daveb/bzr_repo/player_rm2/test2/local/lib/python2.7/site-packages/twisted/internet/defer.py",
line 1099, in _inlineCallbacks
result = g.send(result)
File "icb_error_test1.py", line 37, in intermediate_function3
yield ERROR_MAKER_TO_USE()
File
"/home/daveb/bzr_repo/player_rm2/test2/local/lib/python2.7/site-packages/twisted/internet/defer.py",
line 1228, in unwindGenerator
gen = f(*args, **kwargs)
File "icb_error_test1.py", line 19, in icb_error_maker
raise exception_to_raise
__main__.ExceptionToRaise:
However when ERROR_MAKER_TO_USE = pod_error_maker The output is as follows:
Twisted version [twisted, version 13.2.0]
Python version 2.7.3 (default, Feb 27 2014, 20:00:17)
[GCC 4.6.3]
intermediate_function1 1
intermediate_function2 1
intermediate_function3 1
intermediate_function3 exception ExceptionToRaise()
intermediate_function2 exception ExceptionToRaise()
intermediate_function1 exception ExceptionToRaise()
Unhandled Error
Traceback (most recent call last):
Failure: __main__.ExceptionToRaise:
Questions:
1. Why is it that icb_error_maker raises an exception that retains its
traceback while pod_error_maker does not?
2. How might one retain the inlineCallback trace when handling
Exceptions/Failures from deferreds? (I would prefer a universal method, ie
not doing a Try/Reraise at every yield point) ?
3. I have taken a look at the code in twisted/internet/defer.py and I am
not sure where the distinction between inlineCallback exceptions and
deferred errors are being made. Would someone please elaborate on this
process.
Thanks
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