September 2007
Intermediate to advanced
170 pages
4h 24m
English
Content preview from High Performance Web SitesBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
Chapter 15. Rule 13: Configure ETags
Reducing the number of HTTP requests necessary to render your page
is the best way to accelerate the user experience. You can achieve this by
maximizing the browser's ability to cache your components, but the
ETag header thwarts caching when a web
site is hosted on more than one server. In this chapter, I explain what
ETags are and how their default implementation slows down web
pages.
What's an ETag?
Entity tags (ETags) are a mechanism that web servers and browsers use to validate cached components. Before jumping into the details of ETags, let's review how components are cached and validated.
Expires Header
As the browser downloads components, it stores them in its
cache. On subsequent page views, if the cached component is "fresh,"
the browser reads it from disk and avoids making an HTTP request. A
component is fresh if it hasn't expired, based on the value in the
Expires header. Let's look at an
example.
When a component is requested, the server of origin has the
option to send an Expires header
back in the response:
Expires: Thu, 15 Apr 2010 20:00:00 GMT
Chapter 5 recommends
setting an expiration date in the far future. How far is "far" depends
on the component in question. An ad image might have to expire daily,
whereas a company logo could expire in 10 years. The HTTP
specification (http://www.w3.org/protocols/rfc2616/rfc2616-sec14.html#sec14.21)
suggests servers should not set an Expires date more than one year in the future, but this is a guideline; ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.