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"
        }
      }
    }
  }
}