[uf-rest] AHAH and delay: "push" as "lazy pull"
kmarks at mac.com
Mon Nov 28 15:37:14 PST 2005
On Nov 28, 2005, at 1:57 PM, Dr. Ernie Prabhakar wrote:
> Hi Ryan,
> On Nov 27, 2005, at 9:20 AM, Ryan King wrote:
>>> However, my hypothesis is that you can also implement "push" as
>>> "lazy pull."
>> I'm pretty sure I've seen this hypothesis proven already.
> I know Rohit proposed it a while ago, as Roy alludes to here:
> I'm just not (yet) sure of how generally applicable that is
The underlying 'pending http' model is widely used. In particular, it
is how DAAP (the iTunes sharing protocol) handles synchronising
playlist changes and detecting disconnects -(you need no traffic to
maintain a pending TCP connection, but you do get a teardown message
when it goes).
I also helped Greg Elin build this kind of protocol for his network
chat application over XMLHTTPRequest.
The key to doing it reliably is to use a sequence number in the
requests (not a timestamp, as that has potential skew and races), so
the server knows what you have already got. Also, you should have
exponential backoff and retry on timeouts and other dropped connection
A simple chat app using this might be an interesting bit of sample code.
More information about the microformats-rest