microservice.py

"""
Simple module for microservices.
"""

import configparser
import json
import os

from routes import Mapper
import waitress
import webob
from webob.dec import wsgify
from webob.exc import HTTPNotFound, HTTPCreated, HTTPNoContent


CONFIG_ENV = 'MICRO_SERVICE_CONFIG'
DEFAULT_CONFIG = """
[server]
host = 127.0.0.1
port = 9999
"""


def load_config():
    " Configure a config dict object "
    config = configparser.ConfigParser()
    config.read_string(DEFAULT_CONFIG)
    config_file = os.getenv(CONFIG_ENV)
    if config_file:
        config.read_file(config_file)
    return config


"""
Simple backend representing model layer.
"""
_storage = {}


def retrieve(id=None):
    if id is not None:
        return _storage[id]
    return _storage


def create(object):
    id = str(int(max(_storage or [0])) + 1)
    _storage[id] = dict(object)


def update(id, object):
    for k, v in object.iteritems():
        _storage[id][k] = v


def delete(id):
    del _storage[id]


CONTENT_TYPE = 'Content-Type'
APPLICATION_JSON = 'application/json'
GET = 'GET'
POST = 'POST'
PUT = 'PUT'
DELETE = 'DELETE'


def _parse_body(request):
    """
    Parse the body from a webob `Request` taking the 'Content-Type'
    header into account
    """
    if request.headers.get(CONTENT_TYPE) == APPLICATION_JSON:
        return json.loads(request.body.decode())
    return request.params


def rest(req, id=None):
    " REST(ish) endpoint "
    if req.method == GET:
        try:
            obj = retrieve(id)
        except KeyError:
            raise HTTPNotFound()
        return webob.Response(
            json.dumps(dict(obj)),
            content_type='application/json')
    elif req.method == POST:
        create(_parse_body(req))
        raise HTTPCreated
    elif req.method == PUT:
        try:
            update(id, _parse_body(req))
        except KeyError:
            raise HTTPNotFound
        raise HTTPNoContent
    elif req.method == DELETE:
        try:
            delete(id)
        except KeyError:
            raise HTTPNotFound
        raise HTTPNoContent


routes = Mapper()
routes.connect('/', func=rest)
routes.connect('/{id}', func=rest)


@wsgify
def wsgi_app(req):
    " The actual WSGI application. "
    result = routes.match(environ=req.environ)
    if not result:
        raise HTTPNotFound()
    func = result.pop('func')
    return func(req, **result)


def test():
    " Simple functional test suite. "
    import requests
    global _storage
    _storage = {}
    base_url = 'http://localhost:9999/'

    req = requests.get(base_url)
    assert 200 == req.status_code
    assert {} == req.json()
    print('Empty storage test passed.')

    obj = {'1': '1'}
    req = requests.post(base_url, obj)
    assert 201 == req.status_code
    print('Create object test passed.')

    req = requests.get(base_url)
    assert 200 == req.status_code
    assert {'1': {'1': '1'}} == req.json()
    print('Get all test passed.')

    req = requests.get(base_url + '1')
    assert 200 == req.status_code
    assert {'1': '1'} == req.json()
    print('Get one test passed.')

    req = requests.put(base_url + '1', {'1': '100'})
    assert 204 == req.status_code
    req = requests.get(base_url + '1')
    assert 200 == req.status_code
    assert {'1': '100'} == req.json()
    print('Update test passed.')

    req = requests.delete(base_url + '1')
    assert 204 == req.status_code
    req = requests.get(base_url + '1')
    assert 404 == req.status_code
    req = requests.get(base_url)
    assert 200 == req.status_code
    assert {} == req.json()
    print('Delete test passed.')

    _storage = {}
    obj = {'foo': 1}
    req = requests.post(base_url, json=obj)
    assert 201 == req.status_code
    print('Create JSON object test passed.')

    req = requests.get(base_url + '1')
    assert 200 == req.status_code
    assert {'foo': 1} == req.json()
    print('Get one JSON test passed.')


if __name__ == "__main__":
    import sys
    if 'test' in sys.argv:
        test()
    else:
        config = load_config()
        waitress.serve(
            wsgi_app,
            host=config['server']['host'],
            port=config['server']['port'])