

The problem with Amazon's load balancing (ELB) - maccman
http://leadthinking.com/226-the-problem-with-amazons-load-balancing

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kordless
The title of this post should be "The problem with DNS". It's really the lack
of mapping the root domain to a CNAME that is the issue.

Amazon chose to do load balancing with layer 4, no sessions, and using low
TTLs on CNAME records. This minimal feature set allows them to make the
service highly scalable and fault tolerant. Add more features, and it could
become brittle.

If you build your app or site around naked domains, expect layer 7 support, or
want session persistence, ELB isn't going to work for you very well. On the
other hand, if you build around the set of features they provide, it's likely
to be exactly what you need.

Of course this leaves the issue with someone typing in your naked domain and
getting redirected. I'd point out that this can be solved by using an elastic
(static) IP and always making sure you have that IP address up on a box. If
it's not mapped (and monitoring fails) then bring up a new box and assign it
to that box. Only do 302s on that box to keep things simple.

Alternately you could use something like UltraDNS, which will monitor boxes
for you, and switchero DNS on failures.

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mark_l_watson
Amazon designed and implemented AWS for their own use, and it is not always a
good fit for outside developers. But sometimes it is.

AWS is very good for offloading non-time critical calculations, backup storage
using S3, etc. AWS may not be the best choice for primary hosting, and as
usual requirements analysis is required.

The DNS problem that the article mentions is not a problem for Amazon hosting
their own applications but can be a problem for external users.

