Actually, after further research, I believe the return value from Pool.apply_async needs to be an object defined at the top-level of any module. In the end, I decided to write my own Result class that stores the information available through the arcpy.Result methods and lets you retrieve them with an identical interface. It is picklable if all the inputs and outputs are picklable. For my case, I'm mostly using datasets represented as path strings.
class Result(object):
def __init__(self, status, inputs, outputs, messages):
"""Initializes the result.
ARGUMENT DESCRIPTION
-------- -----------
status The job status.
inputs The inputs to the job.
outputs The outputs of the job.
messages The messages of the job represented as a list of
tuples whose values are (severity, message).
STATUS DESCRIPTION
------ -----------
0 New
1 Submitted
2 Waiting
3 Executing
4 Succeeded
5 Failed
6 Timed Out
7 Cancelling
8 Cancelled
9 Deleting
10 Deleted
SEVERITY DESCRIPTION
-------- -----------
0 Informational Message
1 Warning Message
2 Error Message
"""
self._status = status
"""The job status.
STATUS DESCRIPTION
------ -----------
0 New
1 Submitted
2 Waiting
3 Executing
4 Succeeded
5 Failed
6 Timed Out
7 Cancelling
8 Cancelled
9 Deleting
10 Deleted
"""
self._inputs = inputs
"""The inputs to the job."""
self._outputs = outputs
"""The outputs of the job."""
self._messages = messages
"""The messages of the job represented as a list of tuples whose values
are (severity, message).
SEVERITY DESCRIPTION
-------- -----------
0 Informational Message
1 Warning Message
2 Error Message
"""
@classmethod
def from_arcpy_result(cls, result):
"""Creates a Result from an arcpy.Result instance.
ARGUMENT DESCRIPTION
-------- -----------
result An instance of arcpy.Result.
"""
assert isinstance(result, arcpy.Result), (
"Result %r is not an instance of arcpy.Result." % result)
status = result.status
inputs = [result.getInput(i) for i in range(result.inputCount)]
outputs = [result.getOutput(i) for i in range(result.outputCount)]
messages = []
for i in range(result.messageCount):
messages.append((result.getSeverity(i), result.getMessage(i)))
return cls(status, inputs, outputs, messages)
@property
def inputCount(self):
"""The number of inputs of the job."""
return len(self._inputs)
@property
def maxSeverity(self):
"""The maximum severity of the messages.
SEVERITY DESCRIPTION
-------- -----------
0 Informational Message
1 Warning Message
2 Error Message
"""
return max([severity for severity, message in self._messages])
@property
def messageCount(self):
"""The number of messages."""
return len(self._messages)
@property
def outputCount(self):
"""The number of outputs."""
return len(self._outputs)
@property
def resultID(self):
"""The job ID if the tool is a geoprocessing service, else ""."""
return self._resultID
@property
def status(self):
"""The job status.
STATUS DESCRIPTION
------ -----------
0 New
1 Submitted
2 Waiting
3 Executing
4 Succeeded
5 Failed
6 Timed Out
7 Cancelling
8 Cancelled
9 Deleting
10 Deleted
"""
return self._status
def cancel(self):
"""Cancels the job."""
pass
def getInput(self, index):
"""Returns the input at the given index, either as a record set or a
string.
ARGUMENT DESCRIPTION
-------- -----------
index Index of the input to return.
"""
return self._inputs[index]
def getMapImageURL(self, *args, **kwargs):
"""Returns a map service image for a given output, if one exists."""
raise NotImplementedError
def getMessage(self, index):
"""Returns the message at the given index.
ARGUMENT DESCRIPTION
-------- -----------
index Index of the message to return.
"""
return self._messages[index]
def getMessages(self, severity=0):
"""Returns messages of the given severity or greater.
SEVERITY DESCRIPTION
-------- -----------
0 Informational Message
1 Warning Message
2 Error Message
"""
messages = []
for s, m in self._messages:
if s >= severity:
messages.append(m)
return "\n".join(messages)
def getOutput(self, index):
"""Returns the output at the given index, either as a record set or a
string.
ARGUMENT DESCRIPTION
-------- -----------
index Index of the output to return.
"""
return self._outputs[index]
def getSeverity(self, index):
""""Returns the severity of the message at the given index.
SEVERITY DESCRIPTION
-------- -----------
0 Informational Message
1 Warning Message
2 Error Message
"""
return self._messages[index][0]
