Blog post: http://devinfee.com/blog/2010/11/04/pylons-mongodb-user-registration-login/
Git Repo: https://github.com/dfee/userdemo

Note that the entire PylonsHQ website is also running on CouchDB + Pylons, and is open-sourced: http://bitbucket.org/bbangert/kai/

It uses the raw couchdb access as shown above, in addition to using python-couchdb schema docs which allow it to coerce some values from JSON (like datetime) back to a proper Python form.

I can think of two ways you could approach this.

1. Instead of just incrementing a single value for the counter example, you could create a new document for each visit, then run a map/reduce view to return the total visits.

2. When you update a document in couchdb, it will also send the revision of the document. If you try to update the document, and CouchDB detects a different revision(example: someone else changes the document), it will return an error. You would probably handle this in your application code somewhere, and retry the “transaction”.

As far as scalability….I’m not sure . Wait for a 1.0 release when replication etc,. is all hammered out.

From the CouchDB docs:

To update an existing document, you also issue a PUT request. In this case, the JSON body must contain a _rev property, which lets CouchDB know which revision the edits are based on. If the revision of the document currently stored in the database doesn’t match, then a 412 conflict error is returned.

Any thoughts on how to deal with concurrent requests though? with SQL dbs, we can have transactions and row locking to ensure the counter is in a valid state. Can this be acheived with couchdb backend? and if so, how scalable would it be?

db = couchdb.client.Database(‘http://localhost:5984/tutorial’) did not create db.

To make the code work for me I added in my imports:
from couchdb import Server

immediately following db = couchdb.client.Database(‘http://localhost:5984/tutorial’)
I added:
if not db:
db = Server(‘http://localhost:5984/’).create(‘tutorial’)

Then everything went fine. From a brief bit of looking around it seems that couchdb.client.Database accesses a couchdb database but I don’t think that it creates one if it doesn’t exist. I’m using couchdb 0.8.1 and couchdb-python 0.5