Tag Archives: load balancers

CloudCaster – casting clouds into existence

CloudCaster is my tool to cast clouds into existence in many regions, yet still maintain source-controlled infrastructure specifications.  A single JSON document is used to specify your cloud architecture.  Currently it only supports EC2/VPC/Route53.


This tool is my attempt to capture all the manual steps I was using to create Virtual Private Cloud infrastructure: subnets, routing tables, internet gateways, VPNs, NAT instances, AutoScale groups, launch configs, and Load Balancers.

An example specification is here: https://github.com/WrathOfChris/ops/blob/master/cloudcaster/examples/example.json

In each Availability Zone, it creates a Public subnet and a Private subnet.  The public subnet will contain any ELB’s created, apps specified with the “public” flag, and the NAT instance for the private instances to reach the world.

I wrote this tool for a number of reasons.  I needed a way to specify the state my cloud infrastructure should be in, and be able to re-create the infrastructure setup in case of a catastrophic failure.  Eventually I will need to transition to multi-cloud, and specifying the infrastructure will allow me to adapt other cloud provider APIs when I need them without being locked into a single vendor.  I also wanted to codify many of the best-practices I’ve learned into the automation, so new services are created default-best.


Documentation is located here: https://github.com/WrathOfChris/ops/blob/master/cloudcaster/README.md

Naming is partially-enforced.  Load balancers and AutoScale groups have the environment name postfixed to the name.  Security groups do not (least surprise!).  The concept of a “continent” is just a DNS grouping to allow for delegation to a Global Traffic Manager or second DNS provider.

A sample run consisting of a single app, single elb, and the nat instance would create resources similar to:

Auto Scaling Groups:

$ as-describe-auto-scaling-groups --region us-west-2
AUTO-SCALING-GROUP exampleapp-prod exampleapp-prod-20140106002258 us-west-2c,us-west-2b,us-west-2a example-prod 0 1 1 Default
INSTANCE i-17c3b121 us-west-2b InService Healthy exampleapp-prod-20140106002258
TAG exampleapp-prod auto-scaling-group Name exampleapp-prod true
TAG exampleapp-prod auto-scaling-group cluster blue true
TAG exampleapp-prod auto-scaling-group env prod true
TAG exampleapp-prod auto-scaling-group service example true

Launch Configs:

$as-describe-launch-configs --region us-west-2
LAUNCH-CONFIG exampleapp-prod-20140106002258 ami-ccf297fc t1.micro discovery

Note the date encoded in the LaunchConfig name, this allows CloudCaster to update in place by swapping launch configs.  Next time an instance is terminated, the new instance will be launched from the new Launch Config

Load Balancers:

$ elb-describe-lbs --region us-west-2
LOAD_BALANCER example-prod example-prod-1891025847.us-west-2.elb.amazonaws.com 2014-01-06T00:22:51.910Z internet-facing

Warnings apply – CloudCaster will create instances and load balancers, and that will cost you money.  There is no delete option, you will have to manually delete all resources created.  It is not designed to be a general purpose tool for all your needs – it does exactly what I need, and a little less.

In the example.json, you may notice mention of a “psk” – this is for a future post where I will talk about creating automatic VPNs between VPCs using a VPN concentrator instance and the NAT instances.  For now, you will see that CloudCaster sets route in the public subnets for “privnet” – the overarching private subnet for all your worldwide VPCs.

That’s all for now, I hope you enjoy