ansi c example

How to Implement and Use ANSI C in an Existing OpenWhisk Service

Overview

Integrating ANSI C into an Apache OpenWhisk service allows developers to create high-performance serverless functions using the C language. This guide explains how to implement and use ANSI C in OpenWhisk, leveraging Docker-based runtimes.

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Prerequisites

1. Apache OpenWhisk Deployment: Ensure OpenWhisk is deployed on Kubernetes or another supported platform. Follow deployment instructions[4].
2. Docker Runtime for OpenWhisk: Install OpenWhisk’s Docker runtime to support custom languages[9].
3. ANSI C Environment: Install a C compiler (e.g., GCC) and ensure you can compile and test C programs locally.

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Steps to Implement ANSI C in OpenWhisk

1. Create an ANSI C Program

Write your ANSI C function code. For example, create a file named example.c:

#include 

int main(int argc, char *argv[]) {
    printf("This is an example log message from an arbitrary C program!\n");
    printf("{ \"msg\": \"Hello from arbitrary C program!\", \"args\": \"%s\" }",
           (argc == 1) ? "undefined" : argv[1]);
    return 0;
}

Compile the program locally using:

gcc -o example example.c

2. Prepare a Docker Image for the ANSI C Runtime

Create a custom Docker image that includes the compiled ANSI C program. Use the following Dockerfile:

FROM ubuntu:20.04

RUN apt-get update && apt-get install -y gcc libc-dev

COPY example /usr/local/bin/example

ENTRYPOINT ["/usr/local/bin/example"]

Build and tag the Docker image:

docker build -t openwhisk-ansi-c-runtime .

3. Deploy the Docker Runtime in OpenWhisk

Push the Docker image to a container registry accessible by your Kubernetes cluster:

docker tag openwhisk-ansi-c-runtime /openwhisk-ansi-c-runtime
docker push /openwhisk-ansi-c-runtime

Update your OpenWhisk deployment to include this runtime by modifying its runtime configuration (runtime.json)[9].

4. Register the Action in OpenWhisk

Use the wsk CLI to create an action using the custom runtime:

wsk -i action create ansiCAction --docker /openwhisk-ansi-c-runtime --web true

5. Invoke the Action

Test your action using wsk CLI or via its web URL:

wsk -i action invoke ansiCAction --result --param args "test"

Or access it via its URL:

curl -X POST  -d '{"args": "test"}'

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Benefits of Using ANSI C in OpenWhisk

• Performance: ANSI C provides faster execution compared to interpreted languages.
• Flexibility: Custom runtimes allow tailored solutions for specific use cases.
• Integration: Seamlessly integrates with other OpenWhisk features like triggers and rules[5].

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Additional Notes

• For complex applications, consider integrating external libraries like OPC UA ANSI C Stack for advanced functionalities[6][7].
• Monitor resource usage when deploying high-performance functions with Docker-based runtimes.

By following this guide, you can leverage ANSI C to build efficient serverless functions within Apache OpenWhisk!

Citations:
[1] https://blog.zhaw.ch/splab/2019/03/15/building-a-sample-mqtt-based-application-on-openwhisk/
[2] https://dalelane.co.uk/blog/?p=3741
[3] https://norma.ncirl.ie/5963/1/ankitkumar.pdf
[4] https://www.robertobandini.it/2020/12/13/apache-openwhisk-hello-world/
[5] https://www-inf.telecom-sudparis.eu/COURS/CSC5004/practicals/basics-openwhisk.pdf
[6] https://github.com/linshenqi/UA-AnsiC
[7] https://stackoverflow.com/questions/47394623/client-implementation-using-the-opc-foundation-ansi-c-stack
[8] https://opcfoundation.org/forum/opc-ua-implementation-stacks-tools-and-samples/ansi-c-sample-applications/
[9] https://github.com/apache/openwhisk-runtime-docker/blob/master/sdk/docker/example.c

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