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python-interruptingcow - A watchdog that interrupts long running code.
- Description:
Interrupting Cow
================
Interruptingcow is a generic utility can relatively gracefully interrupt your
Python code when it doesn't execute within a specific number of seconds::
from interruptingcow import timeout
try:
with timeout(5, exception=RuntimeError):
pass
except RuntimeError:
print "didn't finish within 5 seconds"
Timeouts are specified in seconds (as floats with theoretical microsecond
precision).
Installation
------------
::
$ pip install interruptingcow
Reentrant
---------
Interruptingcow is fully reentrant, which means that you can have nested
timeouts::
from interruptingcow import timeout
class Outer(RuntimeError): pass
class Inner(RuntimeError): pass
try:
with timeout(20.0, Outer):
try:
with timeout(1.0, Inner):
try_the_expensive_thing()
except Inner:
do_the_cheap_thing_instead()
except Outer:
print 'Program as a whole failed to return in 20 secs'
Nested timeouts allow a large outer timeout to contain smaller timeouts. If the
inner timeout is larger than the outer timeout, it is treated as a no-op.
Function Decorators
-------------------
Interruptingcow can be used both as inline with-statements, as shown in the
above examples, as well as function decorator::
from interruptingcow import timeout
@timeout(.5)
def foo():
with timeout(.3):
pass
Caveats
-------
Interruptingcow uses ``signal(SIGALRM)`` to let the operating system interrupt
program execution. This has the following limitations:
1. Python signal handlers only apply to the main thread, so you cannot use this
from other threads
2. You must not use this in a program that uses ``SIGALRM`` itself (this
includes certain profilers)
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