Comments on: A Look At Simple Update Protocol (SUP) http://robert.accettura.com/blog/2008/08/28/a-look-at-simple-update-protocol-sup/ Robert Accettura's Personal Blog on Web Development and Tech Fri, 10 Feb 2012 05:07:57 +0000 hourly 1 http://wordpress.org/?v=3.3.1 By: Robert http://robert.accettura.com/blog/2008/08/28/a-look-at-simple-update-protocol-sup/comment-page-1/#comment-437928 Robert Fri, 29 Aug 2008 13:01:52 +0000 http://robert.accettura.com/?p=1917#comment-437928 @Gerv: Not really. To get <code>Last-Modified-Date</code> you still need to do a http request for each and every feed. When your talking about a large site like Flickr or Facebook you can be talking about millions of unnecessary requests. This is enormously wasteful of resources and slow unless you want to hammer Apache. By having a list of what's been updated, they could retrieve content at a quicker interval with much fewer requests. Adding more caching doesn't speed things up, it just creates more data latency. The goal is to get fresh data as quickly and efficiently as possible. This proposal accomplishes that. Using <code>Last-Modified-Date</code> still means making millions of unnecessary calls and a lot of wasted time. @Gerv: Not really. To get Last-Modified-Date you still need to do a http request for each and every feed. When your talking about a large site like Flickr or Facebook you can be talking about millions of unnecessary requests. This is enormously wasteful of resources and slow unless you want to hammer Apache.

By having a list of what’s been updated, they could retrieve content at a quicker interval with much fewer requests.

Adding more caching doesn’t speed things up, it just creates more data latency. The goal is to get fresh data as quickly and efficiently as possible. This proposal accomplishes that. Using Last-Modified-Date still means making millions of unnecessary calls and a lot of wasted time.

]]> By: Gerv http://robert.accettura.com/blog/2008/08/28/a-look-at-simple-update-protocol-sup/comment-page-1/#comment-437720 Gerv Fri, 29 Aug 2008 10:06:59 +0000 http://robert.accettura.com/?p=1917#comment-437720 Isn't this what HEAD requests and Last-Modified-Date headers are for? If the server has resource constraints, it should keep a cache of the last modified dates for frequently-requested URLs. The work needed to keep this cache would be the same or less as the work needed to make a "feed of updates", and would require no client-side changes. Instead of a "table in a database containing the SUP-IDs of changed feeds" have a "table in the database containing the Last-Modified-Date of feeds". And send back Not Changed responses as appropriate. Gerv Isn’t this what HEAD requests and Last-Modified-Date headers are for?

If the server has resource constraints, it should keep a cache of the last modified dates for frequently-requested URLs. The work needed to keep this cache would be the same or less as the work needed to make a “feed of updates”, and would require no client-side changes. Instead of a “table in a database containing the SUP-IDs of changed feeds” have a “table in the database containing the Last-Modified-Date of feeds”. And send back Not Changed responses as appropriate.

Gerv

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