Worky Faye Updates with Backbone.js

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Up tonight, I hope to get multiple updates working with my Backbone.js calendar application when using faye as the persistence layer.

When I make changes, I am sending the update as a message from my Backbone application to the /calendars/update faye channel. The updated information is sent back from the server on the /calendars/changes faye channel:

The problem is that I am not doing anything with that change information. Ordinarily that would not be a problem, but my backend storage is CouchDB. CouchDB really needs that rev attribute. If a subsequent update is sent with the old rev, CouchDB's optimistic locking will kick in and reject the update:

Got response: 409 localhost:5984/calendar/cd823d4aaaf358069f9a800410000b95
{ error: 'conflict',
  reason: 'Document update conflict.' }

So, in my client, I subscribe to the /calendars/changes channel. In the subscription's callback, I use the revision published by the server to update the Backbone model:

    faye.subscribe('/calendars/changes', function(message) {
      console.log('[/calendars/changes]');
      console.log(message);

      var model = calendar.appointments.get(message);
      model.set({rev: message.rev});
      model.set({_rev: message.rev});
    });

With, that, I can update an appointment. And update it again... and it works:

Got response: 201 localhost:5984/calendar/cd823d4aaaf358069f9a800410000b95
{ ok: true,
  id: 'cd823d4aaaf358069f9a800410000b95',
  rev: '7-55b3b95b6996072aa1519b6070cf12b6' }

Got response: 201 localhost:5984/calendar/cd823d4aaaf358069f9a800410000b95
{ ok: true,
  id: 'cd823d4aaaf358069f9a800410000b95',
  rev: '8-a06160ea8bef50bd71d92a73db61c14b' }

Yay! Except... immediately after I see the successful update, I see:

Got response: 201 localhost:5984/calendar/cd823d4aaaf358069f9a800410000b95
{ ok: true,
  id: 'cd823d4aaaf358069f9a800410000b95',
  rev: '8-a06160ea8bef50bd71d92a73db61c14b' }
Got response: 409 localhost:5984/calendar/cd823d4aaaf358069f9a800410000b95
{ error: 'conflict',
  reason: 'Document update conflict.' }

When I update again, I successfully update the record, which is followed immediately by two conflicts:

Got response: 201 localhost:5984/calendar/cd823d4aaaf358069f9a800410000b95
{ ok: true,
  id: 'cd823d4aaaf358069f9a800410000b95',
  rev: '9-c09e4a0a8bbd5cc25a9e67b19b6a254b' }
Got response: 409 localhost:5984/calendar/cd823d4aaaf358069f9a800410000b95
{ error: 'conflict',
  reason: 'Document update conflict.' }
Got response: 409 localhost:5984/calendar/cd823d4aaaf358069f9a800410000b95
{ error: 'conflict',
  reason: 'Document update conflict.' }

Ah. I know what that is. And I will fix it. But first, I need to finish proof reading the recipes that taught me how to solve it.

Recipes with Backbone. Going alpha tonight.


Day #149