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simpleapi

Version: 0.0.5
Author: Florian Schlachter (http://www.fs-tools.de)
license:see LICENSE file for more (simpleapi is licensed under MIT license)
website:http://simpleapi.de
mailinglist:subscribe: simpleapi@librelist.com

This readme is a short (and messy) overview about simpleapi. There is still an almost complete documentation work in progress which will be published on http://www.simpleapi.de soon.

About

simpleapi is an easy to use, consistent and portable way of providing an API within your django project. It supports several output formats (e. g. json, jsonp, xml) and provides a client library to access the API seamlessly from any python application. You can also use nearly every Ajax framework (e. g. jQuery, ExtJS, etc.) to access the API (see more at "Usage in web-apps" in this README).

Server features:

  • provides API-namespaces to bundle methods
  • has dynamic key authentication / ip restriction
  • takes care of type-conversion
  • provides inheritance (create abstract namespaces and use them as superclasses)
  • supports multiple versions of one API
  • provides several output formats (json, jsonp, xml, etc.)
  • can form output for several usages (ie. ExtJS forms, etc.)
  • has features for: caching, throttling, pickling
  • can be extended with your own features

Client features:

  • super simple access to server functions
  • an easy switch between different api versions

Installation

easy_install -U django-simpleapi

From GitHub

git clone git://github.com/flosch/simpleapi.git

Dependencies

  • Python 2.5 or greater
  • simplejson (if you're using Python <= 2.5)
  • python-dateutil

(see requirements.txt as well)

Screencasts

You should watch the screencasts in full screen.

Contact-app:http://vimeo.com/11280195 (good quality: http://bit.ly/cUdogY)

Server example

First example

Let's start with our first simple server implementation. See more below in this README.

handlers.py:

from simpleapi import Namespace

class JobNamespace(Namespace):
    def status(self, job_id):
        # get the job by job_id ...
        return job.get_status()
    status.published = True # make the method available via API

class SMSNamespace(JobNamespace):
    def new(self, to, msg, sender='my website', priority=5):
        # send sms ...
    new.published = True # make the method available via API
    new.constraints = {'priority': int} # ensure that priority argument is of type int

urls.py:

from simpleapi import Route
from handlers import SMSNamespace, FaxNamespace

urlpatterns = patterns('',
    (r'^job/sms/$', Route(SMSNamespace)),
    (r'^job/fax/$', Route(FaxNamespace)),
)

Second example with multiple API versions

handlers.py:

from datetime import datetime
from simpleapi import Namespace, Response, ResponseElement

class JobNamespace(Namespace):
    # you can either use a callable here or provide a list of ip addresses:
    __ip_restriction__ = ["127.0.0.*", "78.47.135.*"]

    # you can either use a callable here (for dynamic authentication) or provide a static key for authentication:
    __authentication__ = "91d9f7763572c7ebcce49b183454aeb0"

    def _get_job_by_id(self, job_id):
        # get the job by job_id
        # this method isn't published to the public and isn't
        # made accessable via API since it's missing the published-flag
        return Job.objects.get(id=job_id)

    def status(self, job_id):
        job = self._get_job_by_id(job_id)
        return job.get_status()
    status.published = True # make the method available via API
    status.constraints = {'job_id': str}

class FaxNamespace(JobNamespace):
    #Send a fax and use a the provided Response object to built a response that
    #can be sent as json/jsonp/xml and parse back to a Response on a python or javascript client
    #The Response object is modeled after ElementTree

    ret = Response()

    #send fax
    if not success:
        ret.add_error("The Fax failed to send")
    else:
        el = ResponseElement("receipts")
        el.text = "The fax was sent on {date}".format(date=datetime.now())

    return ret


class OldSMSNamespace(JobNamespace):
    __version__ = 1

    def new(self, to, msg):
        # send sms ...
    new.published = True # make the method available via API

class NewSMSNamespace(JobNamespace):
    __version__ = 2

    def new(self, phonenumber, message, sender='my website', priority=5):
        # send sms ...
    new.published = True # make the method available via API
    new.methods = ('POST', ) # limit access to POST
    new.constraints = {'priority': int, 'phonenumber': re.compile(r'\+\d{1,4}\ \d{3,6} \d{5,}')} # ensure that priority argument is of type int

urls.py:

from simpleapi import Route
from handlers import OldSMSNamespace, NewSMSNamespace, FaxNamespace

urlpatterns = patterns('',
    (r'^job/fax/$', Route(FaxNamespace)), # Route with exact one namespace
    (r'^job/sms/$', Route(OldSMSNamespace, NewSMSNamespace)), # Route can hold different versions of namespaces
)

The namespace with the highest version is the default one which will be used when the client doesn't provide a version.

Client example with simpleapi's client library

This is how you can access your published methods from any python application:

First example

from simpleapi import Client

SMS = Client(ns='http://yourdomain.tld/api/job/sms/')
new_sms = SMS.new(
    to="+49 123 456789",
    msg="Short test"
)

Second example (with version change)

from simpleapi import Client

SMS = Client(ns='http://yourdomain.tld/api/job/sms/', version=2)
new_sms = SMS.new(
    phonenumber="+49 123 456789",
    message="Short test"
)

SMS.set_version(1) # back to the old API-version (which takes differently named arguments)

new_sms = SMS.new(
    to="+49 123 456789",
    msg="Short test"
)

Configuration and development

Namespace methods

In order to make a method available and callable from outside (the client party) and to configure the called method simpleapi reads some configuration variables for each method. They are configured as follows:

class MyNamespace(Namespace):
    def my_api_method(self, arg1):
        return arg1
    my_api_method.configuration_var = value # <--

The following configuration parameters are existing:

published:make the method available and callable from outside (boolean)
constraints:a dict where you can specify any type of which one parameter must be of. The parameter will be converted into your desired type (if simpleapi cannot, it wil raise an error to the client). You can also define a callable (which gets (namespace, value) passed and must return the new value or any error, like ValueError) or a compiled regular expression (re.compile(r'...'); in this case the value will be checked against the regular expression). See the examples for more.
methods:specifies which HTTP methods are allowed to call the method (a list; by default it allows every method). If you plan to receive a huge amount of data (like a file), you should only allow POST as this can manage "unlimited" data (GET is limited to 1024 bytes which is fairly enough for much function calls though).
outputs:if specified, the output formatters are limited for this method (a list; e. g. useful, if you plan to return values that cannot be serialized by the json-module but can be pickled and compatibility to Ajax and others isn't an issue for you)

Namespace configuration

You can configure your namespaces on an individual basis. This are the supported configuration parameters:

__version__:an integer; important if you want provide different versions of namespaces within one Route (e. g. for introducing improved API methods without breaking old clients which uses the old namespace, see example above). If the client doesn't provide a version, the namespace with the highest will be used.
__ip_restriction__:
 either a list of ipaddresses (which can contain wildcards, e.g. 127.*.0.*) which are allowed to access the namespace or a callable which takes the ipaddress as an argument and returns True (allowed) or False (disallowed). Can be used to keep track of all requests to this namespace and to throttle clients if needed, for example.
__authentication__:
 either a string with a key or a callable which takes the access_key provided by the client. Must return True (allowed) or False (disallowed). If not given, no authentication is needed. It's recommended to use SSL if you plan to use __authentication__.
__outputs__:If given, the namespace is restricted to the given output formatters (a list of strings)
__inputs__:If given, the namespace is restricted to the given input formatters (a list of strings)
__features__:list of activated namespace-features (currently available: throttling, caching)

All parameters are optional.

NamespaceSession

An individual connection-based NamespaceSession is provided within any method call and can be reached via self.session. The following parameters are available:

request:the original request object provided by django
access_key:client's access key
version:client's requested version
mimetype:the mimetype which will be used for the response

Note: All properties are read-only. Any changes made will be ignored.

Example call:

print self.session.access_key

Route configuration

The Route maintains the communcation between calling clients and your API implementation, the Namespace. It is hooked on a specific URL in your urls.py like this:

(r'^job/fax/$', Route(FaxNamespace))

Route takes only namespaces as arguments. If you have different versions of namespaces (see __version__ in Namespacce configuration) you can pass as many namespaces as you want to Route. It will manage automatically all versions and will use the right one for incoming method calls from clients.

This is an example with 2 different namespacs, a basic one (version 1) and a extended one (verison 2), which would break clients which are developed for version 1.

class BookingSystem(Namespace):
    # global configuration for all derived BookingSystem-classes
    pass

class BookingSystem_1(BookingSystem):
    __version__ = 1

class BookingSystem_2(BookingSystem):
    __version__ = 2

Your urls.py should look like:

(r'^api/$', Route(BookingSystem_1, BookingSystem_2))

Whenever a new client wants to use your API without providing a specific version he will be connected to the namespace with the highest version number (in our example version 2). If he provides version 1, he will see automatically BookingSystem_1, if he provides 2, he will get in touch with BookingSystem_2.

In simpleapi's client you can use set_version() or the version-argument at instantiation to define which version you want to use (see example project). The related HTTP parameter is called _version (see HTTP call and parameters for more).

HTTP call and parameters

Clients are able to call the procedures like:

http://www.yourdomain.tld/job/sms/?_call=new&to=012345364&msg=Hello!&sender=from+me
http://www.yourdomain.tld/job/sms/?_call=status&_output=xml&job_id=12345678

The following parameters are used by simpleapi:

_call:method to be called
_output:output format (e. g. xml, json; default is json)
_input:input format
_data:instead of passing every single argument as an own http parameter, you can pass a dictionary/array to _data instead (_input must be defined then; json is recommended).
_version:version number of the API that should be used (see `Route` configuration)
_access_key:access key to the API (only if __authentiation__ in namespace is defined)
_callback:defines the callback for JSONP (default is simpleapiCallback)
_mimetype:simpleapi automatically sets the correct mime type depending on the desired output format. you can set a different mimetype by set this http parameter.

Server's response

If you call a method the server will response as follows:

status:true or false (boolean; indicates whether the call was successful or not)
result:return value of the called function (only if the call was successful)
errors:contains reasons why the call was not successful (list of unicode strings)

Usage in web-apps

Imagine the following server implementation which will be used for the web-app examples:

from simpleapi import Namespace

class Calculator(Namespace):
    def multiply(self, a, b):
        return a*b
    multiply.published = True
    multiply.constraints = {'a': float, 'b': float}

    # example for user-defined callable for the constraints-property
    def check_power(self, key, value):
        # you can even check the values when you accept **kwargs
        # in your API method
        return float(key) # return casted value # simpleapi will take care of any errors raised

    def power(self, a, b):
        return a**b
    power.published = True
    power.constraints = check_power

The next two chapters are covering Ajax (with jQuery) and crossdomain-Requests.

Usage in web-apps (Ajax+jQuery)

If your functions are not limited to an specific output formatter (which is the default) you're able to call the functions (within the same domain) via Ajax (XMLHttpRequest). I prefer using jQuery or ExtJS which makes calling remote functions a snap. The following example is using jQuery:

jQuery.get("/myapi/", {_call: 'multiply', a: 5, b: 10}, function (result) {
    alert('5 * 10 = ' + result);
})

For more informaton on jQuery's ajax capabilities see here: http://api.jquery.com/category/ajax/

See the demo project for an example implementation.

Usage in web-apps (crossdomain)

If you want to call an API method from a third-party page (which isn't located on the same domain as the server API) you cannot use XMLHttpRequest due to browser security restrictions.

In this case you can use simpleapi's JSONP implementation which allows you to call functions and get the result back via a callback. Some Ajax implementations (like jQuery and ExtJS) support transparent Ajax requests which internally uses the <script>-tag to get access to the remote function. In jQuery it looks like:

$.ajax({
    url: "http://127.0.0.1:8888/api/calculator/one/",
    data: {_call: 'multiply', a: 5, b: 10},
    dataType: "jsonp",
    jsonp: "_callback", // needed since simpleapi names his callback-identifier "_callback"
    success: function (result) {
        alert('5 * 10 = ' + result);
    }
})

See the demo project for an example implementation.

Usage of simpleapi's client

The client's class lives in simpleapi.Client. Import it from there and instantiate your client like this:

my_client = Client(ns='http://yourdomain.tld/api/namespace/')

To call a remote function you just use call it the same as you do usually:

my_client.my_remote_function(first="first argument", second_arg=2, third=datetime.datetime.now())

Hint: It's important that you name your arguments, anonymous arguments are prohibited.

The constructor takes following optional arguments:

version:defines the version to be used (if no one is given, the default API version is used)
access_key:defines the access key to the API
transport_type:Change transport type (default is json). You can set 'pickle' here if the other side allows it (pickle must be added to __output__).

Following methods are provided by client instances:

set_ns:set's a new namespace-URL to be used
set_version:changes the version to be used

Following exceptions can be raised by the client instance:

ConnectionException:
 there was a problem during connection establishment or transmission
RemoteException:
 a remote exception was raised

Usage of arguments and **kwargs in your API method

Usually your namespace method looks like this:

def my_api_method(self, a, b, c, d=10):
    return a+b+c+d
my_api_method.published = True

In the request this would cause the following: ?a=1&b=2&c=3 (d is optional).

If you are in need to get "unlimited" parameters you can also use **kwargs (not *args!) in your API method like this:

def sum_it_up(self, **kwargs):
    return sum(map(lambda item: int(item), kwargs.values()))
my_api_method.published = True

kwargs contains all unused parameters. If the request looks like ?var1=195&var2=95&var3=9819&var999=185 kwargs contains all these parameters.

Advice: To check the **kwargs values use a callable for the method's constraints-configuration.

Hint: If you're passing more parameters in your client call than your function signature contains (e. g. in our first example only a, b, c and d) and your function doesn't contain a **kwargs, the client call will fail with an appropriate errormessage.

Error handling on client/server-side

If you want to raise an error and abort execution of your method you can always call self.error(err_or_list). err_or_list is either an unicode string or a list of unicode strings.

In simpleapi client: self.error raises a simpleapi.RemoteException which you can catch to handle the error on the client side (see example for more).

Supported formatters

  • value ("value")
  • JSON ("json", default)
  • JSONP ("jsonp")
  • cPickle ("pickle") - should only be used by trusted parties
  • XML ("xml")

Supported wrappers

Features (take your namespace to a higher level)

Features are adding more functionality and capability to your namespace. There are a few built-in features, but the __features__-configuration especially allows you to extend your namespace. It looks like this:

class MyNamespace(Namespace):
    __features__ = ['throttling', 'caching', MyVeryOwnFeature]

Please see the example projects for a demo use and implementation of Features.

Caching

simpleapi supports caching of function calls. This is pretty useful when you have a lot of calls to cpu/memory/db-intensive methods. You can ask simpleapi to cache the response (the return value) of a function call depending on the given function arguments. To do so, first add caching to the list of namespace-features:

__features__ = ['caching']

Using the namespace-method caching-configuration you can configure how the simpleapi-cache will work:

def delayed_function(self):
    import time
    time.sleep(5)
    return True
delayed_function.published = True
delayed_function.caching = {
    'timeout': 30, # in seconds
    'key': 'delayed_function'
}

The caching-option can either be a boolean or a dictionary with user-defined settings. Timeout defines, after which timeperiod the key will be removed (default is 1 hour). The key defines the caching-key (default-format simpleapi_FUNCTIONNAME) which can either be a string or a callable (with the request object passed).

A md5-generated fingerprint of the given arguments will be appended to the caching key. If your user-defined caching key is delayed_function, the complete key might be delayed_function_0cc175b9c0f1b6a831c399e269772661. The return value of the function is stored pickled.

Note: Don't forget to configure Django for caching (especially CACHE_BACKEND), see more: http://docs.djangoproject.com/en/dev/topics/cache/

Throttling

simpleapi supports throttling by default. Add throttling to __features__ to activate. You can throttle both single methods and namespace calls in general by number of calls per second, minute and hour per client. Please see the example project for a demo implementation.

simpleapi uses django's caching ability. It's recommended that you use a cache backend which supports atomic updates and is pretty fast (ie. memcached).

How to run the demo

  1. Start the server with ./manage.py runserver 127.0.0.1:8888
  2. Start the client python testclient.py

(Make sure simpleapi is in your PATH)

Tips & tricks

  1. Take a look on my example project (example_project/[client|server]) for a first view on how simpleapi works.
  2. Make sure to remove or deactivate the new csrf-middleware functionality of django 1.2 for the Route.
  3. Use SSL to encrypt the datastream.
  4. Use key authentication, limit ip-address access to your business' network or server.
  5. You can set up a simple throtteling by setting a callable to __ip_restriction__ which keeps track on every request of an ip-address (the callable gets the ip-address of the calling party as the first argument).
  6. You can outsource your namespace's settings by creating new vars in your local settings.py file (e. g. NAMESPACE_XY_IP_RESTRICTIONS=["127.0.0.*", ]) and reference them within your namespace (like __ip_restriction__ = settings.NAMESPACE_XY_IP_RESTRICTIONS)

Limitations

  1. The output/return value of a method is limited to the formatter's restrictions. For instance, you cannot return datetime values since they aren't supported by JSON (use datetime.isotime() or datetime.ctime() instead). Applies only if you're not using cPickle in an trusted environment (which supports datetime-objects and more).