Why I Use SaltStack
I am part of a team (along with Bruce Stringer and Jason Swindle) working on an internal application called Graffiti, which provides an easy way for front-line Rackers to record interactions with customers and provide valuable data with each interaction. It also creates a much simpler way for leads to be passed from the front line to the IB sales team here in SMB cloud.
We knew from the start that we wanted this to be an agile cloud application that utilizes all the things a cloud should be. We had some limitations which meant we had to home grow a few solutions. Since this is an internal application, we could not rely on third-party solutions for off loading workloads. We also had to be careful with our security practices, of course. We ended up going with a configuration that utilizes our internal nova solution for hosting in Cloud Servers. The downside to this is no automated backups, no load balancers and no Cloud Files; much to my dismay.<!-- more -->
The configuration we are building out consists of an Nginx load balancer, two web servers running Nginx and a master-master pair of PostgreSQL database servers using pgbouncer for replication. We also utilize a Redis server for some caching and as a sort of rate limiting feature for our API.
So, why SaltStack?
We use SaltStack for many reasons, but the most important are ease of configuration style, open source (no "pay for the pro features;" it’s all free) and a vibrant developer community that has been easy to reach and quick to patch any bugs we found.
We use SaltStack in combination with saltcloud to automagically deploy our infrastructure. We have a single server setup as a Salt Master, with saltcloud configured on it. We configured the states that each server should be in and what each server’s roles should be. With saltcloud, all we have to do is configure a map file that shows what servers should be online and anything else specific about the servers that we need them to have. Here is an example of a map file for saltcloud:
openstack_2GB: - stagredisn001graffiti: grains: env: stag newrelic_env: staging datacenter: dfw node_type: redis
That example would tell saltcloud that there should be a 2GB server called stagredisn001graffiti with the listed salt "grains" configured. With saltcloud all new servers will get kicked with the Salt minion agent already installed and configured to talk to the Salt Master.
If we keep adding servers to that map file, we can have a map of how our entire infrastructure should look, and when we need another node spun up we just add it to that file and run saltcloud again.
The Power of Grains
Another reason we use SaltStack is that it is incredibly powerful for how simple the configuration can be. We use grains heavily because we need nodes to be able to configure their services based on the way other nodes are configured. For example, we need our load balancer to automatically fetch the IP of any web server and add that IP to its pool. We accomplish this with grains.
When a new server comes online we set four main grains:
env newrelic_env datacenter node_type
With these grains set, the load balancer is configured through SaltStack to look for any servers with the web server node_type and that has the SAME env type. This means that we can spin up dev, staging and production servers without having to specifically tell the correct load balancer to add or remove that node. If a new staging node comes online only the other staging nodes look for it and add it to their configuration. That means we can redeploy all three of our environments from nothing to fully functional in minutes. We also have SaltStack configured to load everything from our GitHub repository using release tags, so it is easy to push new changes as well. With this type of setup, any and all changes can be version controlled through git and properly QC'd before running a simple command from the master servers and bringing all of our environments up to date.
That's the power of a DevOps mentality, and the power of properly using version control with infrastructure automation. SaltStack for the win!