openstack/deb-python-taskflow
Code Issues Proposed changes

Allow any of the previous tasks to satisfy requirements.

Browse Source 
Instead of just checking the previous task, allow any of the
previous tasks to provide the requirement for a new task.
This commit is contained in:
Joshua Harlow
2013-05-22 14:51:03 -07:00
parent d4f74720cb
commit afea4f0732
1 changed files with 25 additions and 21 deletions
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46
taskflow/patterns/linear_flow.py
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@@ -33,7 +33,7 @@ def _convert_to_set(items):
class Flow(ordered_flow.Flow):
"""A linear chain of tasks that can be applied as one unit or
rolled back as one unit. Each task in the chain may have requirements
which are satisfied by the previous task in the chain."""
which are satisfied by the previous task/s in the chain."""
def __init__(self, name, tolerant=False, parents=None):
super(Flow, self).__init__(name, tolerant, parents)
@@ -41,31 +41,35 @@ class Flow(ordered_flow.Flow):
def _fetch_task_inputs(self, task):
inputs = {}
if self.results:
(_last_task, last_results) = self.results[-1]
for k in task.requires():
if last_results and k in last_results:
inputs[k] = last_results[k]
for r in _convert_to_set(task.requires()):
# Find the last task that provided this.
for (last_task, last_results) in reversed(self.results):
if r not in _convert_to_set(last_task.provides()):
continue
if last_results and r in last_results:
inputs[r] = last_results[r]
else:
inputs[r] = None
# Some task said they had it, get the next requirement.
break
return inputs
def _validate_provides(self, task):
requires = _convert_to_set(task.requires())
last_provides = set()
last_provider = None
if self._tasks:
last_provider = self._tasks[-1]
last_provides = _convert_to_set(last_provider.provides())
# Ensure that some previous task provides this input.
missing_requires = []
for r in _convert_to_set(task.requires()):
found_provider = False
for prev_task in reversed(self._tasks):
if r in _convert_to_set(prev_task.provides()):
found_provider = True
break
if not found_provider:
missing_requires.append(r)
# Ensure that the last task provides all the needed input for this
# task to run correctly.
req_diff = requires.difference(last_provides)
if req_diff:
if last_provider is None:
msg = ("There is no previous task providing the outputs %s"
" for %s to correctly execute.") % (req_diff, task)
else:
msg = ("%s does not provide the needed outputs %s for %s to"
" correctly execute.")
msg = msg % (last_provider, req_diff, task)
if len(missing_requires):
msg = ("There is no previous task providing the outputs %s"
" for %s to correctly execute.") % (missing_requires, task)
raise exc.InvalidStateException(msg)
def add(self, task):