Add more comments that explain example & usage

Change-Id: I049b47e56d7f859c9b339d4557d4d292b33f2f74
This commit is contained in:
Joshua Harlow
2013-10-11 16:16:22 -07:00
parent bdda31c7f0
commit 0d458d0518

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@@ -35,6 +35,15 @@ from taskflow.patterns import linear_flow as lf
from taskflow import task
# INTRO: This examples shows how a graph_flow and linear_flow can be used
# together to execute non-dependent tasks by going through the steps required
# to build a simplistic car (an assembly line if you will). It also shows
# how raw functions can be wrapped into a task object instead of being forced
# to use the more heavy task base class. This is useful in scenarios where
# pre-existing code has functions that you easily want to plug-in to taskflow,
# without requiring a large amount of code changes.
def build_frame():
return 'steel'
@@ -68,22 +77,35 @@ def install_wheels(frame, engine, engine_installed, wheels):
def trash(**kwargs):
print("Throwing away pieces of car!")
print_wrapped("Throwing away pieces of car!")
def print_wrapped(text):
print("-" * (len(text)))
print(text)
print("-" * (len(text)))
def startup(**kwargs):
# TODO(harlowja): try triggering reversion here!
# If you want to see the rollback function being activated try uncommenting
# the following line.
#
# raise ValueError("Car not verified")
return True
def verify(spec, **kwargs):
# If the car is not what we ordered throw away the car (trigger reversion).
for key, value in kwargs.items():
if spec[key] != value:
raise Exception("Car doesn't match spec!")
return True
# These two functions connect into the state transition notification emission
# points that the engine outputs, they can be used to log state transitions
# that are occuring, or they can be used to suspend the engine (or perform
# other useful activities).
def flow_watch(state, details):
print('Flow => %s' % state)
@@ -99,6 +121,11 @@ flow = lf.Flow("make-auto").add(
task.FunctorTask(build_engine, provides='engine'),
task.FunctorTask(build_doors, provides='doors'),
task.FunctorTask(build_wheels, provides='wheels'),
# These *_installed outputs allow for other tasks to depend on certain
# actions being performed (aka the components were installed), another
# way to do this is to link() the tasks manually instead of creating
# an 'artifical' data dependency that accomplishes the same goal the
# manual linking would result in.
task.FunctorTask(install_engine, provides='engine_installed'),
task.FunctorTask(install_doors, provides='doors_installed'),
task.FunctorTask(install_windows, provides='windows_installed'),
@@ -112,11 +139,18 @@ flow = lf.Flow("make-auto").add(
'windows_installed',
'wheels_installed']))
# This dictionary will be provided to the tasks as a specification for what
# the tasks should produce, in this example this specification will influence
# what those tasks do and what output they create. Different tasks depend on
# different information from this specification, all of which will be provided
# automatically by the engine.
spec = {
"frame": 'steel',
"engine": 'honda',
"doors": '2',
"wheels": '4',
# These are used to compare the result product, a car without the pieces
# installed is not a car after all.
"engine_installed": True,
"doors_installed": True,
"windows_installed": True,
@@ -125,21 +159,28 @@ spec = {
engine = taskflow.engines.load(flow, store={'spec': spec.copy()})
# This registers all (*) state transitions to trigger a call to the flow_watch
# function for flow state transitions, and registers the same all (*) state
# transitions for task state transitions.
engine.notifier.register('*', flow_watch)
engine.task_notifier.register('*', task_watch)
print("Build a car")
print_wrapped("Building a car")
engine.run()
# Alter the specification and ensure that the reverting logic gets triggered
# since the resultant car that will be built by the build_wheels function will
# build a car with 4 doors only (not 5), this will cause the verification
# task to mark the car that is produced as not matching the desired spec.
spec['doors'] = 5
engine = taskflow.engines.load(flow, store={'spec': spec.copy()})
engine.notifier.register('*', flow_watch)
engine.task_notifier.register('*', task_watch)
print_wrapped("Building a wrong car that doesn't match specification")
try:
print("Build a wrong car that doesn't match specification")
engine.run()
except Exception as e:
print("Flow failed: %s" % e)
print_wrapped("Flow failed: %s" % e)