Nomad

What is Nomad?

Lightweight orchestrator written in Go by HashiCorp
Available on most Unix distributions
Allow to deploy containers accross multiple hosts

Nomad architecture

Nomad is separated in two roles: master and client
Masters receive order and transmit them to the clients
Masters ensure the order is respected as much as possible
In our scenario: the master is the client too

Nomad configuration files

Separated according to their usage:

/etc/nomad.d/base.hcl
/etc/nomad.d/client.hcl
/etc/nomad.d/server.hcl

Nomad job definition

job "my-website" {
  datacenters = ["dc1"]
  type = "service"

  update {
    max_parallel = 1
    min_healthy_time = "10s"
    healthy_deadline = "3m"
  }

  migrate {
    max_parallel = 1
    health_check = "checks"
    min_healthy_time = "10s"
    healthy_deadline = "5m"
  }

  group "web-app" {
    count = 4

    restart {
      attempts = 2
      interval = "30m"
      delay = "30s"
      mode = "fail"
    }

    task "nginx" {
      driver = "docker"

      config {
        image = "registry-host:5000/myteam/my-image"
        port_map {
          web = 8080
        }
      }

      resources {
        cpu    = 500
        memory = 1024
        network {
          mbits = 100
          port "web" {}
        }
      }

      service {
        name = "my-webapp"
        tags = ["web"]
        port = "web"
        check {
          name     = "alive"
          type     = "tcp"
          interval = "10s"
          timeout  = "2s"
        }
      }
    }
  }
}