It works by acting as the fallback-route for the containers. For instance, if you have example.com as a container you want to lazy-load, you would add the container, as well as this lazyloader that would act as a lower-priority router for the same domain. If the host is accessed, the lazyloader will work to boot up the container and redirect the user as soon as it's up.

It then monitors the container's network interface. If the network is idle for X minutes, it will stop the container.

Quick-Start

docker-compose

version: '3.5'

services:
  # Example traefik proxy
  reverse-proxy:
    image: traefik:v2.4
    command:
      - --api.insecure
      - --providers.docker
      - --providers.docker.defaultRule=Host(`{{.Name}}.example.com`)
      - --entryPoints.web.address=:80
      - --entryPoints.web.forwardedHeaders.insecure
      - --providers.docker.exposedByDefault=false
    restart: always
    ports:
      - "80:80"     # The HTTP port
      - "8080:8080" # The Web UI (enabled by --api)
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock # So that Traefik can listen to the Docker events

  # Lazy-loader manager
  lazyloader:
    build: .
    labels:
      - traefik.enable=true
      - "traefik.http.routers.lazyload.priority=-100" # Lower router priority. Would only be hit if the app isn't running
      - "traefik.http.routers.lazyload.rule=Host(`whoami.example.com`, `lazyloader.example.com`)"
    environment:
      TLL_STOPATBOOT: true                   # Stop all lazyloaded containers at boot (great for an example)
      TLL_STATUSHOST: lazyloader.example.com # This hostname will display a status page. Disabled by default
    networks:
      - traefik-bridge
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock # Must access docker

  whoami:
    image: containous/whoami
    networks:
      - traefik-bridge
    labels:
      - traefik.enable=true
      - "traefik.http.routers.lazywhoami.rule=Host(`whoami.example.com`)"
      - lazyloader=true
      - lazyloader.stopdelay=30s # Overrides the default

networks:
  traefik-bridge:
    external: true
    name: traefik-bridge

You can run docker-compose up on the above for a quick-start. You will need to alter the domains as needed.

Config

Configuration uses viper and can be specified by either overwriting the config.yaml file or via environment variables with the TLL_ prefix (Traefik lazy loader)

# What port to listen on
listen: :8080

# If set, when access via this hostname, will display status page
statushost: ""

# Enable debug logging
verbose: false

# if true, will stop all running tagged containers when the lazyloader starts
stopatboot: false

# which splash-page asset to use
splash: splash.html

# Container defaults
stopdelay: 5m # How long to wait before stopping container
pollfreq: 10s # How often to check

# This will be the label-prefix to look at settings on a container
# usually won't need to change (only if running multiple instances)
labelprefix: lazyloader

Labels

lazyloader=true -- (Required) Add to containers that should be managed
lazyloader.stopdelay=5m -- Amount of time to wait for idle network traffick before stopping a container
lazyloader.waitforcode=200 -- Waits for this HTTP result from downstream before redirecting user. Can be comma-separated list
lazyloader.waitforpath=/ -- Checks this path downstream to check for the process being ready, using the waitforcode
lazyloader.waitformethod=HEAD -- Method to check against the downstream server
lazyloader.hosts=a.com,b.net,etc -- Set specific hostnames that will trigger. By default, will look for traefik router

Dependencies

lazyloader.needs=a,b,c -- List of dependencies a container needs (will be started before starting the container). Can only be specified on a lazyloader=true container
lazyloader.provides=a -- What dependency name a container provides (Not necessarily a lazyloader container)
lazyloader.provides.delay=5s -- Delay starting other containers for this duration

License

GPLv3