Using Facebook's Batch API...

If you've built any type of Facebook API integration, chances are that you will gravitate towards batching up your API network requests. Since you are allowed a maximum of 20 requests per batch, you can effectively speed-up your overall performance by 14-15x (my own basic measurements) There may also be overall throttle limits to consider, but in general, the performance is a huge boost from sending individual network calls for each request.

While the API documentation is posted at http://developers.facebook.com/docs/api/batch/, there are several things that aren't well documented.

1. You must provide some type of access token to issue Facebook Batch API requests. Even if you have access_token within the query strings of each individual request, Facebook still expects you to provide some type of access_token= in the POST request. You may encounter 404 errors without providing the access_token parameter. The access_token= parameter can either be a user OR application token. While there may be situations where you want to use a user token, what if you wanted to fetch multiple pages with different user tokens? What if the user's token has expired or he/she has changed the password, invalidating this token? For these situations, you can use the application token (http://developers.facebook.com/docs/authentication/), using the technique described in the "App Login" section. The code in Python looks like the following:

def fb_get_app_token():
    """ For Facebook API requests, we need to get an app token to make Graph API calls.  We can't                                                                                                                       
    use fb_get_with_params() since it expects either/and a user/asset, which we don't use.  Also,                                                                                                                       
    the response from Facebook isn't in JSON format so we have to regex parse it."""
    try:
        token_request = urllib.urlencode({ 'client_id': settings.FACEBOOK_APP_ID,
                                           'client_secret': settings.FACEBOOK_SECRET_KEY,
                                           'grant_type': 'client_credentials'
                                           })

        token = urllib2.urlopen("https://graph.facebook.com/oauth/access_token?%s" % token_request).read()
    except urllib2.HTTPError, e:
        logging.debug("Exception trying to grab Facebook App token (%s)" % e)
        return None

    matches = re.match(r"access_token=(?P.*)", token).groupdict()
    return matches.get('token', '')

You can then use this access_token as the fallback access token. 2. Buried within the Batch API section is the "Specifying different access tokens for different operations". The documentation states that the "access_token should be query string or form post parameter". There isn't an example of how to use it, but basically the access_token should be set in the relative_url path.

curl -F ‘access_token=…’ \
     -F ‘batch=[{ “method”: ”GET”, \
                  "relative_url": "me?access_token=ACCESS_TOKEN1", \
                }, \
                { "method": "GET", \
                  "relative_url": "124456?access_token=ACCESS_TOKEN2", \
                }]'

If you try to put a separate "access_token" : "ABC", Facebook won't recognize the token. You must put it in the query string for GET requests:

{ "method": "GET", \
                  "access_token" : ACCESS_TOKEN,
                  "relative_url": "124456?access_token=ACCESS_TOKEN2", \
                }]'

3. The JSON dictionary that is returned must be JSON-decoded twice: once to retrieve the overall response, and then another to decode the 'body' key. The JSON decoder in Python doesn't seem to know how to decode nested dictionaries.