This tutorial demonstrates how to deploy three services with three different Edge-LB pool instances, with one pool instance per service. You would typically implement this type of deployment scenario to provide high availability when you have multiple services with high demand, that require added capacity to ensure reliability and responsiveness, or that involve transaction processing with high resource consumption or performance overhead.

For example, if you have ten services running on a DC/OS™ Enterprise cluster, you might want to configure ten separate Edge-LB pool instances, with one pool per service, to distribute the traffic for all ten services. If a fault occurs with one of the pools in the cluster, the disruption is contained to only affect that service in the pool instance. Other services continue routing traffic to the correct backend instances without interruption.

Before you begin

You must have:

Edge-LB installed as described in the Edge-LB installation instructions.
The core DC/OS command-line interface (CLI) installed and configured to communicate with the DC/OS cluster.
The edgelb command-line interface (CLI) installed.
An active and properly-configured DC/OS Enterprise cluster, with at least one DC/OS private agent node to run the load-balanced service and at least one DC/OS public agent node for exposing the load-balanced service.

Create and deploy the ping sample app

Copy and paste the following JSON settings to create the sample app definition for the ping service in, and save the ping.json file:

{
  "id": "/ping",
  "cpus": 0.1,
  "mem": 32,
  "instances": 1,
  "cmd": "echo \"pong\" > index.html && python -m http.server $PORT0",
  "container": {
    "type": "DOCKER",
    "docker": {
      "image": "python:3"
    }
  },
  "healthChecks": [
  {
    "protocol": "MESOS_HTTP",
    "path": "/",
    "portIndex": 0,
    "gracePeriodSeconds": 5,
    "intervalSeconds": 10,
    "timeoutSeconds": 10,
    "maxConsecutiveFailures": 3
  }
  ],
  "portDefinitions": [
  {
    "protocol": "tcp",
    "port": 0,
    "name": "pong-port"
  }
  ],
  "requirePorts": true
}

Deploy the ping.json sample app definition:
```
dcos marathon app add ping.json
```

Create the ping service-specific pool

Copy and paste the following JSON settings to create the sample pool configuration file for the ping services in, and save the ping-lb-pool.json file:

{
  "apiVersion": "V2",
  "name": "ping-lb-pool",
  "count": 5,
  "haproxy": {
    "frontends": [
    {
      "bindPort": 15001,
      "protocol": "HTTP",
      "linkBackend": {
        "defaultBackend": "ping-backend"
      }
    }
  ],
    "backends": [
    {
      "name": "ping-backend",
      "protocol": "HTTP",
      "services": [
      {
        "marathon": {
          "serviceID": "/ping"
        },
        "endpoint": {
          "portName": "pong-port"
        }
      }
    ]
    }
  ],
    "stats": {
      "bindPort": 0
    }
  }
}

Deploy the Edge-LB pool instance to expose and access the ping service using the ping-lb-pool.json pool configuration file:
```
dcos edgelb create ping-lb-pool.json
```

Create and deploy the nginx sample app

Copy and paste the following JSON settings to create the sample app definition for the NGINX™ service in, and save the nginx.json file:

{
  "id": "/nginx",
  "cpus": 0.1,
  "instances": 1,
  "mem": 128,
  "container": {
    "portMappings": [
      {
        "containerPort": 80,
        "protocol": "tcp",
        "name": "nginx-port"
      }
    ],
    "type": "MESOS",
    "docker": {
      "image": "nginx"
    }
  },
  "networks": [
    {
      "mode": "container/bridge"
    }
]
}

Deploy the nginx.json sample app definition:
```
dcos marathon app add nginx.json
```

Create the nginx service-specific pool

Copy and paste the following JSON settings to create the sample pool configuration file for the nginx services in, and save the nginx-lb-pool.json file:

{
  "apiVersion": "V2",
  "name": "nginx-lb-pool",
  "count": 1,
  "haproxy": {
    "frontends": [
    {
      "bindPort": 15002,
      "protocol": "HTTP",
      "linkBackend": {
        "defaultBackend": "nginx-backend"
      }
    }
  ],
    "backends": [
    {
      "name": "nginx-backend",
      "protocol": "HTTP",
      "services": [
        {
        "marathon": {
          "serviceID": "/nginx"
        },
        "endpoint": {
          "portName": "nginx-port"
        }
      }
    ]
    }
  ],
    "stats": {
      "bindPort": 0
    }
  }
}

Deploy the Edge-LB pool instance to expose and access the nginx service using the nginx-lb-pool.json pool configuration file:
```
dcos edgelb create nginx-lb-pool.json
```

Create and deploy the echo sample app

Copy and paste the following JSON settings to create the sample app definition for the echo service in, and save the echo.json file:

{
  "id": "/echo",
  "args": [
    "-listen", ":80",
    "-text", "\"Hello from Marathon!\""
  ],
  "cpus": 0.1,
  "instances": 1,
  "mem": 128,
  "container": {
    "portMappings": [
      {
        "containerPort": 80,
        "protocol": "tcp",
        "name": "echo-port"
      }
    ],
    "type": "MESOS",
    "docker": {
      "image": "hashicorp/http-echo"
    }
  },
  "networks": [
    {
      "mode": "container/bridge"
    }
]
}

Deploy the echo.json sample app definition:
```
dcos marathon app add echo.json
```

Create the echo service-specific pool

Copy and paste the following JSON settings to create the sample pool configuration file for the echo services in, and save the echo-lb-pool.json file:

{
  "apiVersion": "V2",
  "name": "echo-lb-pool",
  "count": 1,
  "haproxy": {
    "frontends": [
    {
      "bindPort": 15003,
      "protocol": "HTTP",
      "linkBackend": {
        "defaultBackend": "echo-backend"
      }
    }
  ],
    "backends": [
    {
      "name": "echo-backend",
      "protocol": "HTTP",
      "services": [
      {
        "marathon": {
          "serviceID": "/echo"
        },
        "endpoint": {
          "portName": "echo-port"
        }
      }
    ]
    }
  ],
    "stats": {
      "bindPort": 0
    }
  }
}

Deploy the Edge-LB pool instance to expose and access the echo service using the echo-lb-pool.json pool configuration file:
```
dcos edgelb create echo-lb-pool.json
```

Verify deployment status

Verify all services and pool instances have been deployed successfully:
```
dcos marathon app list
```
Verify the pool configuration for frontend and stats ports:
```
dcos edgelb list
```
Verify the Mesos tasks for the services and the Edge-LB pool instances:
```
dcos task list
```

Verify the pool configuration endpoints for each Edge-LB pool:

dcos edgelb endpoints ping-lb-pool
  NAME            PORT   INTERNAL IP
  frontend_port0  15001  10.0.5.202
  stats_port      1025   10.0.5.202

dcos edgelb endpoints nginx-lb-pool
  NAME            PORT   INTERNAL IP
  frontend_port0  15002  10.0.7.138
  stats_port      1025   10.0.7.138

dcos edgelb endpoints echo-lb-pool
  NAME            PORT   INTERNAL IP
  frontend_port0  15003  10.0.7.138
  stats_port      1026   10.0.7.138

Verify service access using frontend ports

Verify that you can access the following deployed services using the public IP address and the assigned frontend ports:
- ping service:
```
http://<public_agent_public_IP>:15001
```
- nginx service:
```
http://<public_agent_public_IP>:15002
```
- echo service:
```
http://<public_agent_public_IP>:15003
```
In this tutorial, the ping load balancing service frontend port is 15001 and the port for HAProxy statistics is 1025. If the public IP address for the public agent node is 34.211.65.249, you could access the service by opening a web browser and specifying 34.211.65.249:15001, and the load balancing statistics for the the service by specifying 34.211.65.249:15001/haproxy?stats.

When you navigate to the public IP address and specified port for each load balanced service, verify that you can see the following pages:
- pong
- Welcome to NGINX
- Hello from Marathon!
If you cannot access one of the pages, check that the Edge-LB frontend ports do not conflict with other ports you are currently using.

If you are deploying multiple Edge-LB pool instances, you should also be sure that the Edge-LB pool instance names are unique. For example, the pool instance names used in this tutorial are ping-lb-pool, nginx-lb-pool, and echo-lb-pool, so that the instance names do not duplicate the pool names used in other examples or tutorials.

Exposing multiple services using multiple pools

How to set up load balancing for multiple services using multiple Edge-LB pool instances