Amazon adds Sticky Sessions!

Amazon announced this morning that their Elastic Load Balancer service now supports sticky sessions. This is a key feature for many web application architectures that keeps one user connected to one server so session-specific information is maintained. ELB is advantageous to a DIY solution because it eliminates two instances (since you need redundancy just as with physical hardware) and it supports automatic scaling. You can specify a minimum of web or application instances but auto-scaling will dynamically spin up additional servers to meet demand and add them to your ELB pool. ELB also works across availability zone providing some insurance against a failure in a single geographic region.

Also announced this morning was Simple Notification Service, which looks like a messaging service that speaks http and email. I’ll be curious to see if/how they solve the email deliverability problem since their net block is pretty widely blacklisted due to the inherent sender reputation problems associated with having lots of unmonitored people sharing IP addresses. SNS offers a free tier for the first 100,000 notifications and 1000 emails sent each month. It’s not clear if this is a beta promotion or will extend to the service once fully launched.

This is good news for ColdFusion applications since CF sessions effectively require stickiness to be performant. This was one of the pieces in our evaluation that we weren’t thrilled about; load balancers are a very hardware-dependent service that use heartbeat pings to check which host should be the primary (and should own the MAC address for the primary IP address associated with the host name). While many people seem to run these instances with success, I would rather use dedicated hardware like ELB but lack of session stickiness was a deal breaker. That eliminates one significant objection/hassle in my book.

A lot of people have told me they are anti-cloud for performance reasons but if we can get the performance necessary at a similar price point today, the cloud will only get faster and cheaper (and more helpful…) over time and I think that’s a long-term win.