5 Feb 2012

Scalr - The Holy Grail of Auto-Scale

Cirronix use Amazon Web Services as core technology for all cloud solutions, for us it's the perfect platform offering robust cost efficiency with ease of administration and development flexibility. That said, it does have it's limits and auto-scaling from live instances is one of them. 
Scalr is an open source or hosted service which addresses this problem directly and delivers a resolution beautifully. Not only does it provide an answer to dynamic auto-scaling but provides a slick interface to an enhanced platform administration toolset, let's take a look at what's on offer.

AWS does provide auto-scaling, and it works very well, however it's only possible from pre-built AMIs (Amazon Machine Instances). If you have a live instance running, and update it, in order to propagate changes to your other already running, auto-scaled instances you to look at other options. Update manually, which is a real pain if you have a sizeable farm running, instigate a Chef or Puppet CI framework, or, create a new base instance, change the farm scaling script and re-launch the server farm. All of these options are time consuming, convoluted and to be honest we all have better things to do.

Creating a server farm in Scalr couldn't easier and once running you can snapshot an updated build and replace all running instances with the new version, quite literally with one-click, it can, and will, save you days of work. 

Scalr provides a whole array of pre-configured server options covering not only the usual suspects (Apache and MySQL etc) but extra roles such as dynamic memcache boxes and/or bespoke builds from base images, it can deliver solutions for both Linux and Microsoft and provides resilient managed load balancing from Nginx as an option against the AWS ELB (Elastic Load Balancer).

The interface GUI is clean and intuitive and provides comprehensive options for every conceivable dynamic (and some). Below is a basic farm with balancer, Apache & MySQL instances.



Fig 1 : The Scalr Roles GUI.

We've just touched on the basics here but Scalr really does deliver the full package (it will even host your DNS). We can't recommend it enough. Yes, the hosted option is a paid for service but at $99 for the entry level package it's a mere fraction of comparative offerings from competitors such as RightScale and personally we think it's a much nicer, much cleaner and much better product, plus for the man hours it saves you it will most definitely pay for itself several times over, of that there is no doubt whatsoever.

Here is a brief overview of Scalr's enhanced services in comparison against base AWS :

Scalr FeatureAWS
Easy instance launch across selected server resource and multi-availability zones.
Yes
DNS management.
Yes
Elastic load balancing.
Yes
Configurable instance scaling to selected load metrics.Yes (via CLI configuration scripts)
Auto MySQL DB Master/Slave scaling in response to pre-set load metrics.
No (Unless the AWS RDS Multi-AZ service is implemented at extra cost).
Dynamic updating of all running instances in a scaling group in response to application changes or updates to a single instance.
No (Requires complex 3rd party management from separate continuous integration systems such as Chef or Puppet).
Scheduled instance state EBS volume snapshotting to S3.No (Requires 3rd party management such as http://autosnappy.com).
Auto re-launch (self repair) of live server instances to the latest snapshot state in response to instance or zone failure.No (Requires downtime for manual EBS volume configuration from snapshots created manually or using AutoSnappy).
GUI based Apache vHost config distributed across all instances.No (Requires on-box vHost config via vhost.conf and apache2.conf edits).
Auto DNS entry updating for launched/replaced/re-launched instances.No (Requires manual updating of Route53 DNS).

The Scalr website is HERE, the superb Wiki HERE and they offer a free 30 day trial so you can have a play first to see just how easy your life could be. Support is not only swift and friendly but when you get a personal eMail response from the founder you know you're dealing with the right sort of people.

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