sync_calculator

Python example for a synchronous service

This is a very simple example of a synchronous service written in Python. It implements a simple calculator behind a SOAP web interface and represents services with defined, short execution times.

For details on the implementation, also read the corresponding tutorial.

Try it out

The calculator methods are deployed as demo services on the platform under the following service URIs:

http://demo/sync/Calculator_add.owl#add_Service
http://demo/sync/Calculator_subtract.owl#subtract_Service
http://demo/sync/Calculator_multiply.owl#multiply_Service

You can use these services in your workflows.

There is also a demo workflow using the calculator service, you can find it on the portal home page under "Demo_Calculator (http://demo/workflow/Demo_Calculator.owl#Demo_Calculator)".

Prerequisites

To build, run, and test this skeleton service, you only need to have Docker installed on your machine. All required software is already bundled in Docker containers.

For further development based on this skeleton, it is highly recommended to use a local Python environment.

Configure, build, and run the service

Configuration

Prior to running the service, have a look at the file env. This file defines environment variables which will be passed into the container. The first one, CONTEXT_ROOT, defines the deployment path of the app relative to root. In SemWES, this path is always made up of two elements:

CONTEXT_ROOT=/<project>-<service_name>

Here, <project> is the project name you log in with, and <service_name> is for you to choose. Please note that <project>-<service_name> must have a maximum length of 32 characters and must consist only of lowercase letters, digits, and hyphens.

You can define further configuration variables which then can be used in the application source code.

Build and run

To compile service source code, pack it into a Docker container, and run the container, run

./rebuildandrun.sh <port>

Choose a port number that is available on your machine.

On the first run, this might take a while since the base container images need to be downloaded and dependencies need to be installed. Subsequent builds will complete significantly faster.

This run script starts the container in daemon mode, meaning that the command returns immediately and that logs are not immediately visible.

Alternatively, run the container interactively via:

docker run -p <port>:80 --env-file=env calculator

Again, choose a fitting port number

Testing the service

Once the container is running, it can be tested by using its published wsdl file to create a SOAP webclient and call methods with it.

This example includes a Python-based client application, found in the test_client/ folder. If you have a local Python 3.x environment, you can simply run python test_service.py (make sure that all dependencies defined in requirements.txt) are installed. Alternatively, the example includes a Python Docker container for executing the test client.

To use the Python container, run

cd test_client
./build.sh      # run only once
./run.sh        # run every time you want to test

You can make changes to test_service.py to test other methods or other deployment locations. Rebuilding the container is not necessary after such changes.

Use this example as a template

To use this example as a template for your own service development, simply copy the source code to another location and start editing. To understand the structure of the code, start with main.py and then read CalculatorService.py.