Automate Load Balancer is a wrapper package for nginx. It provides the front-end for web and API clients to connect to Chef Automate.
Though nginx is capable of implementing complex application logic, the configuration should be kept minimal. If you need to implement application behavior in a load balancer context, implement it in automate-gateway.
The deployment service runs Automate Load Balancer with habitat's relaxed binding mode. This means that the load balancer will run immediately regardless of whether upstreams are up or not. If a new upstream becomes available, habitat will reconfigure and restart the load balancer.
- https://www.habitat.sh/docs/developing-packages/#pkg-binds
- https://www.habitat.sh/blog/2018/05/0560-Release/
We take advantage of the relaxed habitat binding behavior above to integrate the load balancer with optional components. Currently, only Chef Server is available, though others will likely be added in the future.
We separate the configuration of optional upstreams from the main A2
routes. Core A2 routes are defined in the nginx.conf file. Optional
components are defined in COMPONENT_NAME-location.conf and
COMPONENT_NAME-upstream.conf files. The main configuration file loads
them via a glob pattern so the -location.conf and -upstream.conf
parts of the file names are required.
The general pattern to follow for the upstream file is like this:
upstream cs-nginx {
{{ ~#eachAlive bind.automate-cs-nginx.members as |member| }}
server {{member.sys.ip}}:{{member.cfg.port}};
{{ ~else }}
server 127.0.0.1:65535; # force 502
{{ ~/eachAlive }}
}