Flask Avro

This is a simple AVRO IPC endpoint registration extension for Flask.

For information about AVRO checkout:

• https://avro.apache.org/
• http://avro.apache.org/docs/current/spec.html

Usage

This extension allows you to register a AVRO protocol to a specific URL route. This allows you to handle the messages defined in the protocol.

Given a AVRO protocol test.avpr:

{
    "namespace": "org.avro",
    "protocol": "Test",

    "types": [
        {
            "name": "Message",
            "type": "record",
            "fields": [
                {
                    "name": "from",
                    "type": "string"
                },
                {
                    "name": "body",
                    "type": "string"
                }
            ]
        }
    ],

    "messages": {
        "echo_message": {
            "request": [
                {
                    "name":"message",
                    "type":"Message"
                }
            ],
            "response": "string",
            "errors": []
        }
    }
}

An example of a simple Flask app that implements logic for the message echo_message, you could do the following:

from flask import Flask
from flask.ext.avro import FlaskAvroEndpoint

test_avro_endpoint = FlaskAvroEndpoint.from_filename("test", "test.avpr")

@test_avro_endpoint.register("echo_message"):
def handle_test_send(request_message):

    return request_message.get("body")

app = Flask(__name__)

test_avro_endpoint.connect(app, "/")

The above code registers a function that will handle the request message when the endpoint receives a message for echo_message. The function is responsible for also returning the correct object that is required as response of the protocol.

In order to interact with endpoint, the client would use the AVRO IPC Requestor API for your specific language.

For Python, you'll have to install the avro package with pip and then your client could look like this:

from avro.protocol import protocol
from avro.ipc import Requestor, HTTPTransceiver

TEST_PROTOCOL = protocol.parse(open("test.avpr").read()) 
client = HTTPTransceiver("localhost", 9090)
requestor = Requestor(TEST_PROTOCOL, client)

test_message = {
    "from": "Ground Control",
    "body": "Take your protein pills and put your helmet on"
}

response = requestor.request("echo_message", test_message)

client.close()

Test Helpers

This module also includes a test helper to test your Avro endpoints. Normally, when you test your views, you'll want to use the test_flask_app.test_client() to generate requests to your view endpoints. However, creating AVRO request messages is a little cumbersome.

To help facilitate testing, there is a test utility class flask.ext.avro.util.FlaskAvroTestClient. This is a convenience wrapper around the test_client.

Example usage:

from unittest import TestCase
from flask.ext.avro.util import FlaskAvroTestClient

from avro.protocol import protocol

TEST_PROTOCOL = protocol.parse(open("test.avpr").read()) 

class TestAvroEndpoint(TestCase):

    def setUp(self):
        # Generate your test app or pull a created one
        ...
        self.app = test_app

    def test_endpoint(self):

        client = FlaskAvroTestClient(TEST_PROTOCOL, self.app.test_client(), "/")

        test_body = "Take your protein pills and put your helmet on"
        test_message = test_message = {
            "from": "Ground Control",
            "body": test_body
        }

        response = client.request("echo_message", test_message)

        self.assertEqual(test_body, response)