Code development for Custom Container runtimes

How it works

Function Compute supports two invocation methods:

• HTTP calls (recommended): Invoke a function via an HTTP trigger or a custom domain name. Function Compute passes HTTP requests and responses between the client and your HTTP server with minimal transformation.

• API calls: Invoke a function by calling the InvokeFunction operation — for example, through an SDK or an event source. Function Compute converts the InvokeFunction request into an HTTP POST request and forwards it to the fixed path /invoke on your HTTP server.

The request and response format your HTTP server receives depends on the invocation method.

Limitations

HTTP calls (recommended)

Function Compute passes HTTP requests from clients to your HTTP server and passes HTTP responses back to clients in passthrough mode. Some system-reserved fields are not passed. For details, see Limitations.

API calls

When you invoke a function using the InvokeFunction operation, Function Compute converts the request into an HTTP request and forwards it to your HTTP server at the fixed path /invoke.

Sample code

The following Python (Flask) example implements an HTTP server that handles both HTTP calls and API calls. The server listens on port 9000 and handles GET, POST, PUT, and DELETE requests on any path.

import os
from flask import Flask, request

REQUEST_ID_HEADER = 'x-fc-request-id'
app = Flask(__name__)


@app.route('/', defaults={'path': ''})
@app.route('/<path:path>', methods=['GET', 'POST', 'PUT', 'DELETE'])
def hello_world(path):
    # Read the request ID injected by Function Compute
    rid = request.headers.get(REQUEST_ID_HEADER)
    # Read the request body
    data = request.stream.read()
    print("Path: " + path)
    print("Data: " + str(data))
    # Return a response body, status code, and a custom header
    return "Hello, World!", 200, [('Function-Name', os.getenv('FC_FUNCTION_NAME'))]


if __name__ == '__main__':
    app.run(host='0.0.0.0', port=9000)

Key points:

• @app.route('/', defaults={'path': ''}) — handles requests to the root path.

• @app.route('/<path:path>', methods=['GET', 'POST', 'PUT', 'DELETE']) — handles requests to any other path and passes the path value to hello_world as the path parameter.

• request.headers.get(REQUEST_ID_HEADER) — reads the x-fc-request-id header injected by Function Compute into every request.

• request.stream.read() — reads the request body.

• return "Hello, World!", 200, [('Function-Name', os.getenv('FC_FUNCTION_NAME'))] — returns a response body of "Hello, World!", status code 200, and a Function-Name response header sourced from the FC_FUNCTION_NAME environment variable.

What's next

• Configure a custom domain name

• Manage versions

• Manage aliases