how can the webapp query the status of a couchdb node
The main problem is: what to do if replication doesn't work ?
The webapp queries haproxy, and that will query one of the couchdb nodes. even a couchdb node that fails replicating can be queried, but will pass stale docs.
try out this:
curl --netrc-file /etc/couchdb/couchdb.netrc -X GET 'http://127.0.0.1:5984/_membership'
(from redmine: created on 2013-07-02)