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3_Building_the_Consul_Cluster.md

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Chapter 2 - Building the Consul Cluster

Prerequisites

  • A XenServer 7.2 Environment
  • XenCenter 7.2
  • the centos-7-micro template as built in Chapter 1.
  • a workstation with the following

Goal

By the time we have completed this section, you will have a functional three node Consul cluster and be able to inspect its status via the web UI.

Terraform Consul nodes

Create a project directory that will hold your terraform files and states. Since I would like to be able to provision and destroy each infrastructure component individually, I will make a subfolder in my project directory for Consul, Vault, Nomad servers, and Nomad clients.

└── play_cluster
    ├── consul
    ├── nomad-server
    ├── nomad-client
    └── vault

Switch to your consul folder.

Create the consul.tf file

Create a consul.tf file with the following information. Replace placeholders in "«»" with appropriate values from your environment.

provider "xenserver" {
    url = "«XenServer URL»"
    username = "«XenServer user name»"
    password = "«XenServer password»"
}

resource "xenserver_vm" "consul-server-1" {
    name_label = "consul-server-1"
    base_template_name = "centos-7-micro"
    xenstore_data {
      hostname = "consul-server-1.node.consul"
    }
}

resource "xenserver_vm" "consul-server-2" {
    name_label = "consul-server-2"
    base_template_name = "centos-7-micro"
    xenstore_data {
      hostname = "consul-server-2.node.consul"
    }
}

resource "xenserver_vm" "consul-server-3" {
    name_label = "consul-server-3"
    base_template_name = "centos-7-micro"
    xenstore_data {
       hostname = "consul-server-3.node.consul"
   }
}

At this point, you should be able to run terraform plan and see that three resources will be created.

Run terraform apply to build your three nodes.

Install Consul

You can perform these steps on one node at a time or on multiples at once using a tool like cssh (csshX on macOS)

Create the consul user

useradd consul
usermod -aG wheel consul
mkdir /home/consul/.ssh
chown consul /home/consul/.ssh
chmod 700 /home/consul/.ssh
echo "ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDBsCHv5Pyco+HkIDEy/x2WQWikvZ2QBFMUtXgsezFTAyNjsvrdEWgLfK0upQdVNC3Mo20KHtTh6sUSkddlBxdt8IezsjZgUs3DekuZXCEwCeEm8caWewmNwfu4CmnZZjPHjEWMENUmdAw00y3Hn57BuudyUmoMb5ktpwdIjkSPHZHxWACo4jIdgljuOg8Z0z+xcCDzkKtAeEcZPbCyC3i2hm2p1v4GsQ2Np8CI7luM+r+sXEMSraNq5FPJRFE6cEZuTuXpVXha646IWciT8P7bGdQkU89rScB73J9YDBzVzRbnVmTe0VLI2XJ76qgubTvEeFlaJnZsN6+gLLHotRUl [email protected]" > /home/consul/.ssh/authorized_keys
chown consul /home/consul/.ssh/authorized_keys
chmod 600 /home/consul/.ssh/authorized_keys
sudo mkdir /etc/consul.d
sudo chown consul /etc/consul.d
sudo mkdir -p /opt/consul/data
sudo mkdir -p /opt/consul/bin
chown consul /opt/consul
passwd consul

Write Consul Configuration

cat << CONSULCONFIG | sudo tee /etc/consul.d/config.json
{
  "server": true,
  "bootstrap_expect": 3,
  "ui": true,
  "client_addr": "0.0.0.0",
  "retry_join": ["10.0.2.21","10.0.2.22","10.0.2.23"],
  "datacenter": "dc1",
  "data_dir": "/opt/consul/data",
  "log_level": "INFO",
  "node_name": "$(hostname -s)",
  "watches": [
  ]
}
CONSULCONFIG
sudo chown consul /etc/consul.d/config.json

Create the systemd service definition

cat << CONSULSERVICE | sudo tee /etc/systemd/system/consul.service
[Unit]
Description=Consul Server
Requires=network-online.target
After=network-online.target

[Service]
User=root
EnvironmentFile=-/etc/sysconfig/consul
Environment=GOMAXPROCS=2
Restart=on-failure
ExecStart=/usr/local/bin/consul agent $OPTIONS -config-file=/etc/consul.d/config.json
ExecReload=/bin/kill -HUP \$MAINPID
KillSignal=SIGINT
StandardOutput=journal

[Install]
WantedBy=multi-user.target
CONSULSERVICE

Make firewalld rules for consul

sudo firewall-cmd --zone=public --permanent --add-port=8300/tcp
sudo firewall-cmd --zone=public --permanent --add-port=8301/tcp
sudo firewall-cmd --zone=public --permanent --add-port=8302/tcp
sudo firewall-cmd --zone=public --permanent --add-port=8400/tcp
sudo firewall-cmd --zone=public --permanent --add-port=8500/tcp
sudo firewall-cmd --zone=public --permanent --add-port=8600/tcp
sudo firewall-cmd --zone=public --permanent --add-port=8600/udp
sudo firewall-cmd --reload

Enable and start the Consul service

sudo systemctl enable consul.service
sudo systemctl start consul.service

At this point, you should have an three node Consul cluster configuration. You can verify this by going to the Consul Web UI. It is accessible at http://«Consul server IP»:8500/ui/

You can now proceed to build the Vault cluster.