CloudFlare : Java Glossary

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CloudFlare
Introduction Traditional Caching
Distributed Caching CloudFlare Caching
Advantages Requests For Change
Disadvantages Links

Introduction

A company that offers a number of services of interest to people who have websites. Some are free and some cost $20.00 USD a month. For free, they will provide Always Online. If your site goes down, their server takes over and displays a snapshot of your home page, with an explanatory banner. Also for free, they will mirror the static content of your site and serve it to your customers from the nearest mirror. The catch is the static content is updated only every day. For updating every 15 minutes, you have to pay. It does dozens of other things, many of which I have no clue as to their purpose.

Distributed Caching

It also offers CDN (Content Delivery Network) services to cache and serve your static contents from servers all over the world.

CloudFlare offers four types of service plans: Free, Pro $20.00 USD per month, Business $200.00 USD and Enterprise $5000.00 USD . Credit cards only No PayPal.

It will cache your static content at servers around the world to half response time. No matter what the traffic, your bill stays the same. You continue to use your same ISP (Internet Service Provider). You do not install any CloudFlare software on your server. You do not upload content to CloudFlare. You continue to serve your dynamic content direct from your own server.

With the free level, they spider your entire site once a week to prepare a complete cache to use in case your site goes down. You get automatic gzipping even if your server does not support it.

With pro level, you get prefetching so that the first hit is as fast as subsequent ones, priority over free traffic and SPDY (Speedy) support. With business level you get railgun, a super compressor that takes advantage of the fact most dynamic content changes slowly over time, and even updated static content is mostly the same. Basically, it compresses deltas.

Advantages

Disadvantages

Traditional Caching

Even if you don’t use CloudFlare, some of your pages may be cached by anonymous, transparent, caching servers. Your server puts a cache timeout in the header of the pages it sends out. Let’s say it said This page is good for one hour. After that, you had better get a fresh copy. Basically two unpleasant things can happen:

  1. The hour expires, the page is still the same as ever, but the cache does an unnecessary fetch of a fresh page (or at least does a probe).
  2. After 15 minutes, the page is updated. But the cache keeps serving the old version for another 45 minutes.

To succeed, your server needs ESP (Extra Sensory Perception) to guess when each page will next be updated. The essential problem is the cache protocol provides no way for the server to notify cachers that a page has been freshly updated and they should invalidate their cached copy, or that a page who timeout has expired still has not changed.

CloudFlare Caching

CloudFlare can cache using the same tools as any other cacher, however, it has some extra tools available to control it.

  1. At the CloudFlare website, Clear the cache for the URL after updating the file, this will take effect worldwide within seconds. You would need to do this once for each file, each time you update. This would not be practical for routine use, unless you automated the process. You would use this if you had accidentally uploaded some embarrassing page and wanted it replaced immediately.
  2. Enable development mode. This will turn off caching for your entire site and invalidate caches world wide for all your files.
  3. Have CloudFlare cache such files for a shorter time and let them expire naturally. You can do this using Page Rules for the URL (Uniform Resource Locator) pattern you want to cache. This overrides the timeouts your server is applying, at least for CloudFlare. Note you can also use Page Rules to tell CloudFlare not to cache at all.
  4. Have your server return shorter Cache-Control max-age values or Expires headers in the HTTP (Hypertext Transfer Protocol) Response. This would apply to all caching not just that done by CloudFlare.

So, in summary, cache expiry is controlled three ways:

  1. By traditional cache timeout headers applied by your server.
  2. By overriding the cache timeout rules at CloudFlare.
  3. By forcing a global cache invalidate for a particular file at the CloudFlare website.

What CloudFlare could do in future is allow you to send them a list of files you, or give you a utility you can feed them to. It would then broadcast the invalidate requests, filtering out the invalidates that would happen naturally within 10 minutes.

One slightly awkward thing, you must persuade your ISP to reconfigure the DNS (Domain Name Service) name servers to use CloudFlare’s.

Requests for Change

Summary

The documentation and support are exemplary. It is not only clear, it is aethesthetically laid out. The people who designed this website are true pros. They are also willing to explain how it works. I am very impressed by these people. There are so many companies now who consider their customers as unavoidable nuisances.

cloud
hit counters
ISP
Railgun overview
web stats
Which extensions does CloudFlare cache? So there are a number of ways you can ensure you see the latest file:
Wikipedia on CloudFlare

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