Wikiedu's Hashistack Setup

This repository contains the Terraform configuration for Wikiedu.

This configuration:

• Creates a datacenter on Linode, connected by Consul.
• Creates a Nomad cluster.
• Spins up the necessary resources (redis, mariadb, memcached) for powering the WikiEdu Rails app.

Steps to Spin Up a New Datacenter

1. Create a secrets.tfvars file in the linode and nomadservers directories. See secrets.tfvars.example and variables.tf for more information.
2. Ensure all binaries (below) are on your PATH
3. terragrunt run-all init
4. terragrunt run-all apply
5. Point subdomains to the address of your new nginx node.
6. Run the provided ssl provision script (in nomadserver ) on the nginx node.
7. waypoint init && waypoint up from the WikiEd project directory.

Binaries required

1. Waypoint (0.3)
2. Terraform (0.15)
3. Terragrunt (0.28.21)
4. ssh-keyscan and scp

Using Waypoint Exec

You may connect to any container running the rails app with waypoint exec.

However, once inside the container, you must prefix all commands with /cnb/lifecycle/launcher in order to set $PATH correctly and get all of your actually-installed Rubies/gems/etc, rather than using the system versions.

Scaling Strategy

Rails and Sidekiq workloads: If you're running out Sidekiq capacity (queues getting backed up) or Rails capacity (HTTP queue latency reported is unacceptable, say 150milliseconds or more), you should add additional "no volume" nodes by increasing the task group count to provide more resources, then change the rails jobspec file in the WikiEdu repo or use the nomad job scale command.

• More NGINX capacity If Nginx is running out of CPU, resize the node (in linode/main.tf). This will take about 5 minutes and will cause hard downtime. You will then need to increase the cpu/memory allocation in the Nomad jobfile for Nginx.
• More Redis or Memcache capacity. Update the appropriate variables that control CPU/memory allocation. If that means that you have no available space in the cluster topology, provision additional nodes in linode/main.tf.
• More MariaDB capacity. Resize the node. This will cause hard downtime of 5 minutes or more. You will need to update the cpu/memory allocation in the mariadb job spec. It is intended that the mariadb job takes all of the resources on its node.