Run a workflow from an external program - Adder example

This example shows how to develop a simple workflow and call it from an external program. The workflow will perform an addition of two numbers specified as String parameters, storing the result in a Table dataset. The workflow will be called from a Python script using the PySimpleSoap Web Services client.

Build the Adder workflow

Create a new workspace named WebServices, and add a new workflow named Adder to the workspace. Add an Execute SQL action to the Adder workflow, and use the Define Action Parameters Wizard to add two String parameters named x and y to the action.

Add x, y and Result nodes to the workflow, and set numeric values for the x and y parameters. The workflow should now look like this:

Adder example - Execute SQL action.

Set the Execute SQL action’s Statements property to the following. Each SQL statement should be stored as a separate string entry.

CREATE TABLE Result(Answer Int)

INSERT INTO Result SELECT x + y

Add an Extract Fields action to the workflow. Link its Source property to the Result dataset, and add a Result1 dataset to the action. Edit the action’s Columns to Params property and set it to a table row containing the following values:

Answer, Result1

Rename the Result1 parameter node to Sum. The workflow should now look like this:

Adder example - Extract Fields action.

Run the workflow and verify that the Sum dataset contains the correct result.

Register the workflow as a Web Service

Use the Register Workflow as Web Service Wizard to register the Adder workflow as a Web Service. Select both x and y in the Choose Input Parameters screen, and Sum in the Choose Output Parameter screen.

Download and Install Python

Download Python 2.7.3 from the Python Programming Language Official Website at http://python.org. Run the installation program, and then set your Windows path variable to include the directory location of the PYTHON.EXE executable.

Verify the installation by entering python in a command window.

C:\>python

Python 2.7 (r27:82525, Jul 4 2010, 09:01:59) [MSC v.1500 32 bit (Intel)] on win32

Type "help", "copyright", "credits" or "license" for more information.

>>>

Download and install the PySimpleSoap web services client

Download the PySimpleSoap 1.0.5 source package from http://code.google.com/p/pysimplesoap/downloads/list and extract the ZIP file to a temporary directory. To resolve a ‘timeout isn't supported’ error that may occur when running the Web Services client, follow these steps:

Edit the <Download dir>\ pysimplesoap-1.05a\pysimplesoap\client.py file.
Change the line that reads:

TIMEOUT = 60

TIMEOUT = None

Save the client.py file.

Install the PySimpleSoap web services client from a command window by running the following from the <Download dir>\pysimplesoap-1.05a directory:

python setup.py install

Create the Python script

Create a new file named Adder.py. Paste in the following code and save the file.

# Adder.py

# Python LiveCompare web services client.

# Import the web services client.

from pysimplesoap.client import SoapClient

# Import date and time functions.

import datetime

# Import a 'sleep' function.

import time

# Workflow status strings.

COMPLETED = 'COMPLETED'

RUNNING = 'RUNNING'

QUEUED = 'QUEUED'

FAILED = 'FAILED'

UNRECOGNIZED_TOKEN = 'UNRECOGNIZED_TOKEN'

# Set WSDL to the link to your Web Service, obtained from the Web Services screen.

WSDL = 'http://localhost/livecompare/WebServices/Adder.lcsx?WSDL'

TRACE = False

# Set the web services client.

client = SoapClient(wsdl=WSDL, trace=TRACE)

# Start the workflow, passing in the input parameter values.

# swr stores the StartWorkflow() result.

swr = client.StartWorkflow(x='80', y='20')

status = ''

# Obtain the workflow token.

token = swr['StartWorkflowResult']['token']

# Obtain the recommended polling interval.

interval = swr['StartWorkflowResult']['interval']

# Obtain the EndWorkflow() result in order to check the workflow status.

ewr = client.EndWorkflow(token=token)

# Repeat until a break is reached.

while True:

	# Print the date and time, and the current workflow status.

	status = ewr['EndWorkflowResult']['status']

	print datetime.datetime.today(), status

if status == FAILED:

	break

# Workflow started but an error occurred while it was running.

if status == COMPLETED:

	break

# Workflow ran to completion.

if status == UNRECOGNIZED_TOKEN:

	break

# Invalid workflow token.

# Sleep for the recommended polling interval.

time.sleep(interval)

# Obtain the EndWorkflow() result.

ewr = client.EndWorkflow(token=token)

# If the status is 'COMPLETED' print out the workflow result.

if status == COMPLETED:

	print datetime.datetime.today(), ewr['EndWorkflowResult']['workflowResult']

Test the script

To test the script, run the following from a command window:

python Adder.py

Verify the script results.

C:\temp>python Adder.py

2012-09-17 10:58:48.586000 RUNNING

2012-09-17 10:58:50.658000 COMPLETED

2012-09-17 10:58:50.661000 {'Sum': u'100'}