[uf-rest] AHAH and delay: "push" as "lazy pull"
ryan at technorati.com
Sun Nov 27 09:20:30 PST 2005
On Nov 27, 2005, at 9:03 AM, Dr.Ernie Prabhakar wrote:
> On Nov 26, 2005, at 2:42 PM, Kevin Marks wrote:
>> Ernie, what was the thinking behind adding the delay to AHAH?
> A very good question, since I haven't done anything with it yet. :-)
> The most important point to note is that the *default* behavior
> remains the same:
>> It turns what was an async on demand call to one that polls at
>> intervals, but only on success?
> That is, you can use the function as today as merely "async on
> demand" if you don't specify a delay.
> However, my hypothesis is that you can also implement "push" as
> "lazy pull."
I'm pretty sure I've seen this hypothesis proven already.
> That is, rather than having a separate open socket on the client,
> you merely do a non-blocking pull that the server is smart enough
> to defer resolving until there's new data, a la:
> The idea is that the server would hold the request until it had
> something new to respond with. I added the delay so that it
> wouldn't bury the server with requests in the case where it
> (mistakenly) responded immediately.
> This originally came up in the context of "pubsub" and "Jabber" --
> two protocols that tend to think in terms of "push"; I wanted to
> see whether there was a "clean" way to implement them in terms of
> HTTP and, specifically, AHAH.
>> There are scenarios where this can make sense - ie if there are
>> multiple clients that can update the state of a resource on the
>> server, and you want a persistent connection open to react to this
> Yeah, that sort of thing. Basically, any scenario where the client
> wants 'instant' notification. The main advantage over polling is
> that it requires much less use of network resources. That said, it
> does hold a connection on the server, which consumes server
> resources. On the other hand, I still suspect the overall impact
> is less than if the server had to implement 'true' push (vs. this,
> what, "pseudo-push").
There's one little problem with using this in browsers- most (I
think) browsers will constantly look like its loading a page, which
can be quite unsettling to users.
> Again, I haven't even tested the code yet to make sure it works,
> much less done any detailed studies of its resource impact. If
> you're feeling brave, let me know how it works. :-)
> -- Ernie P.
ryan at technorati.com
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