MailChimp OAuth2: Invalid Mailchimp API Key - wrong datacenter - library may not support datacenter mapping scheme

Question

I have successfully implemented a one time pass through MailChimp's (MC) six step OAuth2 process, documented at http://apidocs.mailchimp.com/oauth2/, using Python and Django. The problem is I want my users to be able to authorize MC once and then I will use that authorization to make calls to MC in the future (with their permission, of course).

Here's how I am doing it:

Step 1: Redirect use to the MC authorize URI.

(works fine)

Step 2: User enters their MC credentials.

(works fine)

Step 3: User gets redirected back to a URI on my server, and
Step 4: I make a request to the MC access token URI, and
Step 5: MC returns an access token.

headers = {                                                                                 
    'User-Agent': 'oauth2-draft-v10',                                                       
    'Content-Type': 'application/x-www-form-urlencoded',                                    
    'Host': 'login.mailchimp.com',                                                          
    'Accept': 'application/json'                                                            
}                                                                                           
payload = {                                                                                 
    'grant_type': 'authorization_code',                                                     
    'client_id': settings.MAILCHIMP_CLIENT_ID,                                              
    'client_secret': settings.MAILCHIMP_CLIENT_SECRET,                                      
    'code': code,                                                                           
    'redirect_uri': settings.MAILCHIMP_REDIRECT_URI                                         
}                                                                                           

response = requests.post(settings.MAILCHIMP_ACCESS_TOKEN_URI, headers=headers, data=payload)
response_dict = response.json()                                                             
access_token = response_dict['access_token']

At this point I save the access_token, the datacenter-less API key, in my database.

Step 6: I make a request to the MC metadata URI to get a datacenter.

Note that this step occurs multiple times as I need to make MC calls on the user's behalf, whereas Steps 1-5 only occur once.

headers = {'Authorization': 'OAuth ' + access_token}                                        
response = requests.get(settings.MAILCHIMP_METADATA_URI, headers=headers)                   
response_dict = response.json()                                                             
dc = response_dict['dc']

Step 7: I construct an API key and make MC calls using the Python library.

mkey = access_token + '-' + dc
mcapi = mailchimp.Mailchimp(apikey=mkey)

mcapi.do_something_fun_with_mailchimp()...

The problem is that the final step intermittently returns the error,

Invalid Mailchimp API Key: <key>-dc . You are accessing the wrong datacenter - your client library may not properly support our datacenter mapping scheme.

What am I doing wrong?

Answer 1

My workflow is correct, except that I only need to do it once. I can store the access_token and the datacenter (key-dc) in my database and use it for future calls.

Although I still don't know exactly what was causing my problem, I now know that it was not related to this workflow. It's correct.

Answer 2

I think the Endpoint in the client library is "http://.api.mailchimp.com" so you need to send the token as only access token as per this part from documentation:

api_endpoint - this is http://.api.mailchimp.com. If you don't have a datacenter aware wrapper, use this api endpoint and the access_token as your API Key.