Server setup

EBW serves the site through an HAProxy proxy server. This enables HAProxy metrics, the serving of other websites on the same server if desired, and the enabling of various http/s best-practices (timeouts, server and client limits) that can be implemented at the proxy layer, rather than being coded in the Go server.

Ansible configuration

The default HAProxy setup is configured through the Ansible scripts, particularly the haproxy role. In tools/ansible/roles/haproxy/tasks/main.yml the installation is defined. It might be instructive to look through that role definition file through this discussion:

  1. Steps install-haproxy through install-certbot install haproxy and certbot from Ubuntu repos and the Let’s Encrypt repo.
  2. Steps create-haproxy-lua-dir through copy-haproxy-lua-script install the acme-validation plugin for HAProxy from This plugin allows HAProxy to handle certbot signature validation requests without interrupting HAProxy.
  3. Step stop-haproxy-systemd disables HAProxy, and get-certificate fetches a certificate for the server’s fqdn, using the certbot standalone server (this because we’ve not yet fully configured HAProxy).
  4. merge-certificate merges the certbot acquired certificates into a format required by HAProxy.
  5. configure-haproxy does the configuration of HAProxy, and notifies Ansible that HAProxy should be restarted (this will occur at the end of the installation).
  6. Finally cron-letsencrypt configures the Let’s Encrypt certificate renewal, using the script received from the lua plugin repo.

HAProxy configuration

HAProxy is configured from the template tools/ansible/roles/haproxy/templates/haproxy.cfg.j2. The file is largely self-explanatory, while a few inlined comments describe particular configurations.