pushlets: joining comet movement
justb4
With great interest I have been following recent COMET developments and
would like to join cometd developments in whatever way.
Back in 1999 I have created Pushlets (www.pushlets.com), first as a
hack, pushing HTML slides as a teacher in a classroom setting, later as
an OSS project on SF. From the start I've been using the
"hidden-iframe-trick", streaming JS function calls over a permanent
HTTP connection. AFAIK this was the first use of this technique. Later
on several other projects emerged like mod_pubsub.
Over the past 7 years the Pushlets framework evolved, though slowly due
to my other obligations like http://www.geotracing.com (that uses
Pushlets as well), into a more generic HTTP-based publish/subscribe
framework. The most recent addition is an AJAX (XHR-based) client
library. There is also a protocol spec (not up2date):
http://www.pushlets.com/doc/protocol.html
Yes, I am aware of the scalability limitations of the Pushlets
framework. A dedicated server-side technique based on NIO (such as
Greg, hi there, is working on ?) could help. In this context Pushlets
support three modes of operation that clients can indicate: 1) stream,
2) poll and 3) pull. Especially "pull" I tend to use a lot. "pull" is
basically like fishing: request is held until data becomes available or
a timeout. The request is re-issued after a random (configurable) time.
Another feature is that clients can indicate the encoding format they
would like to receive: JS callback, XML, Java Serialized and (planned)
JSON. This way the protocol can be used in an assortment of clients
like Flash, mobile Java apps, even command-line wget etc.
I see similarities with the cometd protocol. Looking into the future it
would be great if we could have a common protocol supported by clients
such as DOJO and implemented by various server side technologies, like
Pushlets ;-). Developers that would like to join the Pushlet project
for COMET development are more than welcome.
Ok, a long intro just to say hi. best,
Just van den Broecke
www.justobjects.nl