News: Archive

2008-01-31 - 2008-02-28

Ajatus Lightning talk @ FOSDEM

Jerry Jalava 08/02/08 21:14:01

Ajatus LT was accepted to this years FOSDEM in Belgium.

At this point it seems the presentation will be on Sunday 24 at 15:40.

I'll be introducing Ajatus itself and little bit about the pieces it is built on (CouchDB, jQuery).
Mostly I try to concentrate the presentation for developers interested either in offline AJAX development or even Ajatus itself.
I will be showing and explaining some of the layers inside Ajatus, different ways to expand it with plugins, etc and give sneak peak to the future of the app.
Some basic replication scenarios will be covered also.

At the same weekend Bergie and I will be attending the XMPP Devcon to collect and present our ideas of the automated XMPP based CouchDB replication currently going under name PillowTalk. 

 

Conferences this spring

Henri Bergius 16/02/08 21:46:37

While last autumn was more quiet, this spring seems to have a number of events that I'm going to:

Looking forward to meeting many of you in these events! The July conferences of GUADEC in Istanbul and State of the Map in Limerick sound interesting as well.

It is possible to follow my movements through Dopplr:

Dopplr travel map


Technorati Tags: ajatus, geoclue, obooe

Offline web applications: a technology trend of 2008

Henri Bergius 20/02/08 18:33:41

MIT Technology Review's 10 Emerging Technologies of 2008 report includes offline web applications as a rising trend. When developing Ajatus, our new P2P personal CRM the offline issue was often in our minds. We even wrote in the manifesto:

Ideas may come to you when you're sitting in a bus, boarding an airplane or visiting a hospital. For a CRM to work the data must be available and editable in any situation.

Having now dogfooded Ajatus for almost two months, I have to say this has been an important aspect. It is powerful to have all your customer and project data with you at all times, and still be able to use it via the familiar web UI.

Ajatus 0.6 running on Fluid SSB

Offline is useful. You can write your notes in every meeting, update them in train, report expenses as they incur. And most importantly, as long as your computer is running, the application is never down. And still, though replication your data will be safe with your peers or the corporate server.

This is aspect even more important when you start running the app on ultra-portable devices, or go outside the industrialized world.


Technorati Tags: ajatus, offline, web, replication

XMPP publish/subscribe for Midgard and Ajatus replication

Henri Bergius 24/02/08 14:33:46

On the side of FOSDEM we went today to the XMPP devcon held here in Brussels. In there we started formulating our ideas of XMPP publish/subscribe (XEP-0060) based replication for both Midgard and Ajatus.

This post contains very early ideas, but we would be happy to get some feedback on them.

Basic idea

Each Midgard or Ajatus server runs a "synchronization daemon" which is connected to a XMPP server using some JID identity.

The sync daemon registers a set of pub/sub nodes corresponding to the content structure on the Midgard or Ajatus instance:

  • in Midgard: Sitegroups, MgdSchema types, paths (possibly a regexp), approval state
    • /midgard_article/all, /midgard_article/approved
  • in Ajatus: tags

The pub/sub nodes can be set up with some access control rules. For example, Ajatus tags would by default require "whitelist" authorization to subscribe.

When content is changed, the sync daemon gets notified about it (via D-Bus signals in Midgard, and via CouchDb external indexer API in Ajatus). The content object (and immediate children like parameters and file attachments) is serialized into the syndication format and sent onward as a XMPP "pub" leaf. If the object appears on multiple nodes (multiple Ajatus tags for instance), the "pub" leaf is sent to all of them.

XMPP server and the federated network will then handle notifying the subscribers of the nodes about the new leaf.

The subscribers will receive the leaf, and unserialize it to the Ajatus or Midgard database.

Communication between sync daemon and application

The sync daemon should exist as an entity separate from the actual user application. Communication between the sync daemon and Midgard or Ajatus should happen via the application database.

This means that XMPP pub/sub whitelists for Ajatus tags would be maintained in the ajatus_db (non-replicated) database, and the sync daemon would read them from there. The Jabber server credentials would also be stored in the same database.

Information about resources from jabber buddies

User's replication partners are stored as local contacts in the application database. In Ajatus this means "Contacts" and in Midgard "midgard_person" objects. Both storage models have optional JID field.

If JID is marked for a contact, the sync daemon should at startup (or at an interval) try to discover if the contact has pub/sub resources available.

Content transformation in replication stage

While mainly intended for Midgard-to-Midgard and Ajatus-to-Ajatus replication, the same mechanisms could work across different systems.

For this, the sync daemon on the subscribing end should support XSLT transformations before content is unserialized into the system. The XSLT transformation templates should be configurable per subscription.

Hermod / Hermóðr (Midgard replication)

  • "in Norse mythology, messenger of the gods. He was a son of the principal god, Odin, and his wife, Frigg. Known as Hermod the Swift, he was called upon by the other gods when they had a task requiring speed and urgency." - Encyclopedia Britannica
  • Written in Python
    • Using twisted framework or x60br XMPP library
    • using standard Midgard MgdSchema object serialize/unserialize methods
  • How to proof-of-concept before D-Bus? Some watcher in MidCOM? (watcher touches spool file)

PillowTalk (Ajatus and CouchDb replication)

  • Written on Erlang
  • Extendable through plugins
    • Content parsers (Midgard2Ajatus, Ajatus2Midgard)
    • Security
    • CDATA JSON block or convert to XML? (Decision of the content parser?)

Technorati Tags: ajatus, midgard, jabber, replication, synchronization, xmpp

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