Python SDK for CloudEvents

NOTE: This SDK is still considered work in progress, things might (and will) break with every update.

Package cloudevents provides primitives to work with CloudEvents specification: https://github.com/cloudevents/spec.

Parsing upstream Event from HTTP Request:

import io

from cloudevents.sdk.event import v02
from cloudevents.sdk import marshaller

m = marshaller.NewDefaultHTTPMarshaller()
event = m.FromRequest(
    v02.Event(),
    {
        "content-type": "application/cloudevents+json",
        "ce-specversion": "0.2",
        "ce-time": "2018-10-23T12:28:22.4579346Z",
        "ce-id": "96fb5f0b-001e-0108-6dfe-da6e2806f124",
        "ce-source": "<source-url>",
        "ce-type": "word.found.name",
    },
    io.BytesIO(b"this is where your CloudEvent data"), 
    lambda x: x.read()
)

Creating a minimal CloudEvent in version 0.1:

from cloudevents.sdk.event import v01

event = (
    v01.Event().
    SetContentType("application/json").
    SetData('{"name":"john"}').
    SetEventID("my-id").
    SetSource("from-galaxy-far-far-away").
    SetEventTime("tomorrow").
    SetEventType("cloudevent.greet.you")
)

Creating HTTP request from CloudEvent:

from cloudevents.sdk import converters
from cloudevents.sdk import marshaller
from cloudevents.sdk.converters import structured
from cloudevents.sdk.event import v01

event = (
    v01.Event().
    SetContentType("application/json").
    SetData('{"name":"john"}').
    SetEventID("my-id").
    SetSource("from-galaxy-far-far-away").
    SetEventTime("tomorrow").
    SetEventType("cloudevent.greet.you")
)
m = marshaller.NewHTTPMarshaller(
    [
        structured.NewJSONHTTPCloudEventConverter()
    ]
)

headers, body = m.ToRequest(event, converters.TypeStructured, lambda x: x)

HOWTOs with various Python HTTP frameworks

In this topic you'd find various example how to integrate an SDK with various HTTP frameworks.

Python requests

One of popular framework is 0.2-force-improvements.

CloudEvent to request

The code below shows how integrate both libraries in order to convert a CloudEvent into an HTTP request:

def run_binary(event, url):
    binary_headers, binary_data = http_marshaller.ToRequest(
        event, converters.TypeBinary, json.dumps)

    print("binary CloudEvent")
    for k, v in binary_headers.items():
        print("{0}: {1}\r\n".format(k, v))
    print(binary_data.getvalue())
    response = requests.post(url,
                             headers=binary_headers,
                             data=binary_data.getvalue())
    response.raise_for_status()


def run_structured(event, url):
    structured_headers, structured_data = http_marshaller.ToRequest(
        event, converters.TypeStructured, json.dumps
    )
    print("structured CloudEvent")
    print(structured_data.getvalue())

    response = requests.post(url,
                             headers=structured_headers,
                             data=structured_data.getvalue())
    response.raise_for_status()

Complete example of turning a CloudEvent into a request you can find here.

Request to CloudEvent

The code below shows how integrate both libraries in order to create a CloudEvent from an HTTP request:

    response = requests.get(url)
    response.raise_for_status()
    headers = response.headers
    data = io.BytesIO(response.content)
    event = v02.Event()
    http_marshaller = marshaller.NewDefaultHTTPMarshaller()
    event = http_marshaller.FromRequest(
        event, headers, data, json.load)

Complete example of turning a CloudEvent into a request you can find here.

SDK versioning

The goal of this package is to provide support for all released versions of CloudEvents, ideally while maintaining the same API. It will use semantic versioning with following rules:

• MAJOR version increments when backwards incompatible changes is introduced.
• MINOR version increments when backwards compatible feature is introduced INCLUDING support for new CloudEvents version.
• PATCH version increments when a backwards compatible bug fix is introduced.