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923Re: [json] Re: jsonrequest and HTTP/1.1 message pipelining

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  • Mark Nottingham
    Jan 1, 2008

      Personally, I wouldn't go this way; you're making a bet that the
      overhead of setting up SSL/TLS is less than that of working
      synchronously. If you're just POSTing stuff to the server, combining
      several things into one request format may be the way to go.

      That having been said -- if you are going to use https, you'll need to
      have an API available that guarantees to give you a single connection
      back. XHR doesn't do that.

      I totally agree that pipelining is useful, and reducing latency is a
      good goal. It's just that the proper place to fix this sort of thing
      is lower in the stack, not higher.


      On 01/01/2008, at 7:24 AM, Tyler Close wrote:

      > Hi Mark,
      > I think message ordering and pipelining are really useful features, so
      > I'ld like to kick this around some more to see if there's something
      > that could work. For example, I've seen some web applications that
      > implement their own request boxcarring to compensate for the lack of
      > pipelining. At this point, they are basically tunneling their own
      > protocol through HTTP and so not getting many of the benefits of HTTP,
      > such as caching.
      > On Dec 18, 2007 9:06 PM, Mark Nottingham <mnot@...> wrote:
      > > There are several aspects, but if you have an outstanding request
      > on a
      > > connection, and another request is queued, deciding whether it's
      > more
      > > efficient to pipeline or to open a new connection (or, to wait for
      > > the other connection to clear) isn't always a simple thing to do. If
      > > the outstanding request takes a long time to process (either because
      > > the response is very large, or because it takes a lot of server-side
      > > processing time), it may be better to use your other connection.
      > Seems like this logic is something that should be expressed by the end
      > client. So if the client issued requests like:
      > JSONRequest.post(...);
      > JSONRequest.post(...);
      > it's saying there is no expected ordering and the browser should use
      > separate connections if possible. Whereas if the client issued
      > requests like:
      > var c = JSONRequest.ordered();
      > c.post(...);
      > c.post(...);
      > it's saying these requests must be ordered and the browser should
      > pipeline over a single connection if possible.
      > > > How about this: If there is no HTTP proxy, pipeline requests;
      > > > otherwise, send the requests one at a time. So if the client asked
      > > > that requests be ordered, this is guaranteed and performance is
      > best
      > > > effort. If the client doesn't care about ordering, but wants best
      > > > performance, then it uses separately instantiated JSONRequest
      > objects.
      > > > Sound good?
      > > >
      > > You don't always know whether there's an intermediary there;
      > > interception proxies (aka "transparent proxies") and HTTP
      > accelerators
      > > aren't apparent to the client.
      > OK then, SSL to the rescue. For the case where the client asks that
      > requests be sent in order:
      > 1. If its an HTTPS connection, open a single connection and pipeline
      > the requests.
      > 2. Otherwise, open a single connection and send requests
      > synchronously.
      > For requests that don't use the ordered request API, they can be sent
      > as they currently are, over multiple connections.
      > This seems like a small amount of complexity to add, while gaining the
      > benefits of message ordering and pipelining when making secure
      > web-applications.
      > I suppose there could be some server-side infrastructure that again
      > "helps" the developer by re-ordering requests, but the web-application
      > developer is presumably in a better position to do something about
      > this. Are there any other gremlins?
      > Thanks,
      > --Tyler
      > --
      > Use web-keys for RESTful access-control:
      > http://waterken.sourceforge.net/
      > Name your trusted sites to distinguish them from phishing sites.
      > https://addons.mozilla.org/firefox/957/

      Mark Nottingham mnot@...
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