Enable horizontal scaling of queue workers from docker compose (#2100)

Introduce a new environment variable `NUM_WORKERS` that allows us to
specify how many queue workers should be created by docker compose.

Also reconfigure these queue workers to restart automatically upon
failure.

.env.example

@@ -9,6 +9,7 @@ MIX_APP_URL="${APP_URL}"
 # The following two variables are only used for docker compose production installations.
 SSL_CERTIFICATE_FILE=/etc/ssl/certs/ssl-cert-snakeoil.pem
 SSL_CERTIFICATE_KEY_FILE=/etc/ssl/private/ssl-cert-snakeoil.key
+NUM_WORKERS=1
 
 # database.php
 DB_DATABASE=cdash

docker/docker-compose.production.yml

@@ -8,15 +8,18 @@ services:
  - "${SSL_CERTIFICATE_FILE}:/var/www/my-cert.pem"
  - "${SSL_CERTIFICATE_KEY_FILE}:/var/www/my-cert.key"
  worker:
+ env_file:
+ - ../.env
  image: kitware/cdash-worker
- container_name: cdash_worker
  build:
  context: ..
  target: cdash-worker
  environment:
  DB_HOST: database
  deploy:
- replicas: 1
+ replicas: ${NUM_WORKERS:-1}
+ restart_policy:
+ condition: any
  depends_on:
  cdash:
  condition: service_healthy

docs/docker.md

@@ -69,6 +69,7 @@ To set up a CDash production instance using docker compose, follow these steps:
  - `APP_URL=https://<my-cdash-url>`
  - `SSL_CERTIFICATE_FILE=</path/to/certs/my-cert.pem>`
  - `SSL_CERTIFICATE_KEY_FILE=</path/to/certs/my-cert.key>`
+ - `NUM_WORKERS=<desired number of queue worker replicas, defaults to 1>`
 * For postgres only, edit `docker/docker-compose.postgres.yml` and uncomment the `worker` section.
 * Run this command to start your CDash containers:
 ```bash