NGINX Plus Integration with AWS Auto Scaling groups -- nginx-asg-sync

nginx-asg-sync allows NGINX Plus to support scaling when load balancing AWS Auto Scaling groups: when the number of instances in an Auto Scaling group changes, nginx-asg-sync adds the new instances to the NGINX Plus configuration and removes the terminated ones.

More details on this solution are available in the blog post Load Balancing AWS Auto Scaling Groups with NGINX Plus.

Below you will find instructions on how to use nginx-asg-sync.

Supported Operating Systems

We provide packages for the following operating systems:

Ubuntu: 14.04 (Trusty), 16.04 (Xenial)
CentOS/RHEL: 7
Amazon Linux

Support for other operating systems can be added.

Setting up Access to the AWS API

nginx-asg-sync uses the AWS API to get the list of IP addresses of the instances of an Auto Scaling group. To access the AWS API, nginx-asg-sync must have credentials. To provide credentials to nginx-asg-sync:

Create an IAM role and attach the predefined AmazonEC2ReadOnlyAccess policy to it. This policy allows read-only access to EC2 APIs.
When you launch the NGINX Plus instance, add this IAM role to the instance.

Alternatively, you can use the AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY environmental variables to provide credentials to nginx-asg-sync.

Installation

To install nginx-asg-sync:

Download a software package for your OS with the latest version of nginx-asg-sync from the Releases page.
Install the package:

For Amazon Linux or CentOS/RHEL, run: $ sudo rpm -i <package-name>.rpm

For Ubuntu, run: $ sudo dpkg -i <package-name>.deb

Configuration

As an example, we configure NGINX Plus to load balance two AWS Auto Scaling groups -- backend-group-one and backend-group-two. NGINX Plus routes requests to the appropriate Auto Scaling group based on the request URI:

Requests for /backend-one go to Backend One group.
Requests for /backend-two go to Backend Two group.

NGINX Plus Configuration

upstream backend-one {
   zone backend-one 64k;
   state /var/lib/nginx/state/backend-one.conf;
}

upstream backend-two {
   zone backend-two 64k;
   state /var/lib/nginx/state/backend-two.conf;
}

server {
   listen 80;

   status_zone backend;

   location /backend-one {
       proxy_set_header Host $host;
       proxy_pass http://backend-one;
   }

   location /backend-two {
       proxy_set_header Host $host;
       proxy_pass http://backend-two;
   }
}

server {
    listen 8080;

    root /usr/share/nginx/html;

    location = / {
        return 302 /status.html;
    }

    location = /status.html {
    }

    location /status {
        access_log off;
        status;
    }

    location /upstream_conf {
        upstream_conf;
    }
}

We declare two upstream groups – backend-one and backend-two, which correspond to our Auto Scaling groups. However, we do not add any servers to the upstream groups, because the servers will be added by nginx-aws-sync. The state directive names the file where the dynamically configurable list of servers is stored, enabling it to persist across restarts of NGINX Plus.
We define a virtual server that listens on port 80. NGINX Plus passes requests for /backend-one to the instances of the Backend One group, and requests for /backend-two to the instances of the Backend Two group.
We define a second virtual server listening on port 8080 and configure the NGINX Plus APIs on it, which are required by nginx-asg-sync:
- The on-the-fly API is available at 127.0.0.1:8080/upstream_conf
- The status API is available at 127.0.0.1:8080/status

nginx-asg-sync Configuration

nginx-asg-sync is configured in the file aws.yaml in the /etc/nginx folder. For our example, we define the following configuration:

region: us-west-2
upstream_conf_endpoint: http://127.0.0.1:8080/upstream_conf
status_endpoint: http://127.0.0.1:8080/status
sync_interval_in_seconds: 5
upstreams:
 - name: backend-one
   autoscaling_group: backend-one-group
   port: 80
   kind: http
 - name: backend-two
   autoscaling_group: backend-two-group
   port: 80
   kind: http

The region key defines the AWS region where we deploy NGINX Plus and the Auto Scaling groups.
The upstream_conf and the status_endpoint keys define the NGINX Plus API endpoints.
The sync_interval_in_seconds key defines the synchronization interval: nginx-asg-sync checks for scaling updates every 5 seconds.
The upstreams key defines the list of upstream groups. For each upstream group we specify:
- name – The name we specified for the upstream block in the NGINX Plus configuration.
- autoscaling_group – The name of the corresponding Auto Scaling group.
- port – The port on which our backend applications are exposed.
- protocol – The protocol of the traffic NGINX Plus load balances to the backend application, here http. If the application uses TCP/UDP, specify stream instead.

Usage

nginx-asg-sync runs as a system service and supports the start/stop/restart commands.

For Ubuntu 14.04 and Amazon Linux, run: $ sudo start|stop|restart nginx-asg-sync

For Ubuntu 16.04 and CentOS7/RHEL7, run: $ sudo service nginx-asg-sync start|stop|restart

Troubleshooting

If nginx-asg-sync doesn’t work as expected, check its log file available at /var/log/nginx-aws-sync/nginx-aws-sync.log.

Building a Software Package

You can compile nginx-asg-sync and build a software package using the provided Makefile. Before you start building a package, make sure that the following software is installed on your system:

make
Docker

To build a software package, run: $ make <os> where <os> is the target OS. The following values are allowed:

amazon for Amazon Linux
centos7 for CentOS7/RHEL7
ubuntu-trusty for Ubuntu 14.04
ubuntu-xenial for Ubuntu 16.04

If you run make without any arguments, it will build software packages for all supported OSes.

Support

Support from the NGINX Professional Services Team is available when using nginx-asg-sync.

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