The CurrCon Java Applet displays prices on this
web page converted with today’s exchange rates into your local international currency,
e.g. Euros, US dollars, Canadian dollars, British Pounds, Indian Rupees…
CurrCon requires an up-to-date browser
and Java version 1.8, preferably 1.8.0_121.
If you can’t see the prices in your local currency,
Troubleshoot. Use Firefox for best results.
A company that offers a number of services of interest to people who
websites. Some are free and some cost
a month. For free, they will provide Always Online.
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
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.
It also offers
CDN (Content Delivery Network)
services to cache and serve your static contents from servers all over
CloudFlare offers four types of service plans: Free, Pro
per month, Business
. Credit cards only
It will cache your static content at servers around the world to half
time. No matter what the traffic, your bill stays the same. You
continue to use your
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
content direct from your own server.
With the free level, they spider your entire site once a week to
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
ones, priority over free traffic and
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.
Users around the world will get snappy response time.
Search engines spidering your site will get snappy response and
will not put a heavy load on your server.
It will take the mother of all
DOS (Denial of Service attack)
attacks to take you down.
Very little disruption.
You don’t have to install any software at all on your
server. However, if
you sign up for the business level and use railgun,
need to install its compression engine on your server to rapidly get
your site to CloudFlare.
If your site goes down, popular pages will continue to work and
will get a site is down page.
The support people respond quickly and thoroughly. So many
don’t even read their queries. They just dispense pages from
the website the
users have already read based on noticing a few keywords.
It will implement
IPv6 (Internet Protocol Version 6)
even if your server does not, so people can visit your site with
FTP (File Transfer Protocol) is rather flat-footed about uploading files that your users
are downloading. The upload simply fails. With caching, your server
is less busy so FTP has a better chance of finding a file it is trying
to upload idle.
cheques. No Money
orders. No prepayment. No cash (is that legal?). Credit cards only.
This is a
show-stopper for me. This reminds me of a SciFi story I read as a
teenager. In it
the hero goes into a store and wants to pay cash. The clerks are
them, cash implied criminal enterprise. One offers to take the cash
at a steep
discount and put the purchase on his personal credit card. The
extremely strange at the time.
With the pro level you can get
SSL (Secure Sockets Layer),
but the end user sees CloudFlare’s
certificate, not yours.
Your server does not see hits of pages served from cache. It also
pre-fetches as if they were hits from real people. This means your
page-hit statistics are not meaningful. If you sign up for the
you get raw transaction logs from which you can compute individual
statistics, with regional breakdowns even, but not otherwise. If you
accurate page-hit counts you will need some scheme that embeds
pages and reports back to some server when the end user receives the
cache. My experience with such services is they greatly slow down
negating the effect of CloudFlare. This is discouraging me from
trying even the
Even if you don’t use CloudFlare, some of your pages may be
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
is good for one hour. After that, you had better get a fresh copy.
Basically two unpleasant things can happen:
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).
After 15 minutes, the page is updated.
But the cache
keeps serving the old version for another 45
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 can cache using the same tools as any other cacher,
however, it has
some extra tools available to control it.
At the CloudFlare website, Clear
the cache for the URL after updating the file, this will take
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
process. You would use this if you had accidentally uploaded some
page and wanted it replaced immediately.
mode. This will turn off caching for your entire site and
invalidate caches world wide for all your files.
Have CloudFlare cache such files for a shorter time and let them
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
Rules to tell CloudFlare not to cache at all.
Have your server return shorter Cache-Control max-age values or
HTTP (Hypertext Transfer Protocol)
Response. This would apply to all caching not just that done by
So, in summary, cache expiry is controlled three ways:
By traditional cache timeout headers applied by your server.
By overriding the cache timeout rules at CloudFlare.
By forcing a global cache invalidate for a particular file at the
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
requests, filtering out the invalidates that would happen naturally
One slightly awkward thing, you must persuade your
to reconfigure the
DNS (Domain Name Service)
name servers to use CloudFlare’s.
Requests for Change
Accept forms of payment other than credit cards.
Provide some way to get accurate per-page hit counts at the pro
and business levels.
Use long cache timeouts with a way to submit files just uploaded
to the server
to invalidate. I have some static content that goes for months at a
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
I am very impressed by these people. There are so many companies now
who consider their customers as unavoidable nuisances.