docker-cloud-nginx-load-balancing

Dynamic Nginx Load Balancing for Docker Cloud

All Docker Cloud services are acessible through Docker Cloud's API, this allows us to use Docker Cloud's API for automated service registration & service discovery.
No linking or port exposing required. When services stop, start, or scale in Docker Cloud, willrstern/docker-cloud-nginx containers will notice their private IP addresses.
This allows willrstern/docker-cloud-nginx containers to dynamically load balance all services with NGINX_LB ENV variables set.
If a config fails, it will use the last-good-config. See Slack integration.

1) Docker Cloud Setup

Create 2 node clusters on Docker Cloud, one with the deploy tag of apps and one with the deploy tag of nginx.

As the names imply, you will give all of your apps, services, databases, etc an apps deploy tag, while only willrstern/docker-cloud-nginx containers get the nginx tag. This way, nginx will always be on the exact same IP addresses, so DNS can be assigned to those IP addresses.
Send all of your DNS entries & subdomains to the nginx node IP addresses. (NOTE: DynDNS (dyn.com) supports active failover for IP addresses in case a node goes down, this is a great solution for DNS)

2) Running the Load Balancer

Run one or more copies of willrstern/docker-cloud-nginx on Docker Cloud.

add the nginx deploy tag & choose the every node strategy.
Choose the autorestart always option as well.
MAKE SURE to choose the Full Access API role on the Environment Variables page or the load balancer won't be able to detect running services via the Docker Cloud API.
Set NGINX_LB_NAME=prod env variable.
Set CONTAINER_LIMIT env variable if running more than 25 containers.

The Nginx service will now listen to Docker Cloud's stream API. As services change, this LB will balance services with the NGINX_LB=prod env var. A new Nginx configuration is generated & tested with nginx -t. If Nginx accepts the new configuration, it will reload nginx.

3) Load Balancing a Service

Simply run your services on Docker Cloud with the NGINX_PORT, NGINX_VIRTUAL_HOST and NGINX_LB environment variables set in your Dockerfile:

ENV NGINX_LB prod
ENV NGINX_VIRTUAL_HOST test.com,othersite.com
ENV NGINX_PORT 3000

When your service starts, willrstern/docker-cloud-nginx will notice each container and immediately reload it's config!

NOTE: Apps don't need to expose ports to be load balanced! Docker Cloud gives each container an IP, so don't add EXPOSE to your Dockerfile.

4) SSL Termination

create a cert
concatenate the .key and .crt files
replace newlines with \\n and copy the output

openssl req -x509 -newkey rsa:2048 -keyout mysite.key -out mysite.crt -days 1080 -nodes -subj '/CN=*/O=My Company Name LTD./C=US'
cat mysite.key mysite.crt > mysite.combined.crt
awk 1 ORS='\\\\n' mysite.combined.crt

add the combined key & cert into NGINX_CERTS env var to your Dockerfile

ENV NGINX_CERTS -----BEGIN RSA PRIVATE KEY-----\\nMIIEogIBAAKCAQEA...and so on

If you have multiple NGINX_VIRTUAL_HOSTs, add a cert for each host with , in-between: i.e.

ENV NGINX_VIRTUAL_HOST mysite.com,othersite.com
ENV NGINX_CERTS <mysite.com key & cert>,<othersite.com key & cert>

ENV NGINX_VIRTUAL_HOST mysite.com,othersite.com
# only do SSL on othersite.com
ENV NGINX_CERTS ,<othersite.com key & cert>

5) Slack Integration

Before reloading a config, it runs nginx -t to make sure it is valid
If a config fails, it will continue using the last-good-config until a working config is generated
Add SLACK_WEBHOOK=https://hooks.slack.com/services/T02RK... env var to get notifications when a config fails.

Local Development Workflow

Set the DOCKERCLOUD_AUTH & NGINX_LB_NAME environment variables and run npm start:

$ DOCKERCLOUD_AUTH="Basic ...." NGINX_LB_NAME=prod npm start

It will now watch your Docker Cloud cluster for events and generate a config to ./default.conf

How do I get the DOCKERCLOUD_AUTH variable?
- Run any service on Docker Cloud with the Full Access API role on the environment variables page.
- Now inspect the running service's Environment Variables tab to see the DOCKERCLOUD_AUTH value.

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