nginx-aslb

Simple Ngnix container for tesging active/stdby load balancing.

Rationale

The Azure Load Balancer unfortunately does not provide features such as weighed load balancing nor active/stdby setups with TCP healthchecks.

You can use this container and run it on an App Service for Containers in order to replace the Azure LB for this use case.

Features

Active/Standby http load balancing

using embedded TCP checks
will redirect to the primary backend unless it is unavailable, switching to fallback backend when this occurs
restoration to primary if primary is available again

Healcheck URL

In order to check the health of your loadbalancer by the underlying container structure you can use the /_lbcheck url. If the container is running it will reply with a 200 HTTP code with the following payload :

{ "status":"healthy" }

Configuration

The configuration, as for all docker containers is performed via the environnement variables.

The following mandatory variables must be provided :

Env Var Name	Purpose
LB_PORT	Load balancing service port, usually 80 or 8080
LB_BACKEND_PRIMARY	host:port of the primary serving workload
LB_BACKEND_FALLBACK	host:port of the fallback serving workload

Usage

Running locally

In order to run the container locally, serving an entry point with port 8080 and redirecting to backends located under 192.168.4.1:8081 and 192.168.4.1:8082 you can use the following procedure :

echo "LB_PORT=8080" >> vars.txt
echo "LB_BACKEND_PRIMARY=192.168.4.1:8081" >> vars.txt
echo "LB_BACKEND_FALLBACK=192.168.4.1:8082" >> vars.txt
docker pull zlatkoa/nginx-alsb:1.0.0
docker run -p 8080:8080 --env-file vars.txt -d --name lbexample zlatkoa/nginx-alsb:1.0.0

Note : you can use a set of Helloer to simulate your backends.

Running on Cloud Infra

Please make sure the you provide the LB_PORT, LB_BACKEND_PRIMARY and LB_BACKEND_FALLBACK envronnement variables to your pod/container deployement descriptor.

Distribution

For containerized deployements you can use the image available on the Docker Hub. It is updated by the Github CI/CD worklow on each code change.

You can get the container image by issuing the following commands :

docker pull zlatkoa/nginx-alsb:1.0.0