Simple docker-compose.yml example to scale up containers

README.md

Scaling Up Docker Containers and Load Balancing

Simple example to scaling up Docker containers (spawning multiple containers) and load balancing them using Nginx and Traefik.

Scaling up

To scale myapp service up to 3 containers, use --scale.

docker compose up --scale myapp=3 --detach

To provide this service as one (expose as one port), you need a load balancer such as Nginx or Traefik.

Note: the myapp service is a container that simply returns its current host name.

https://github.com/KEINOS/imhost @ GitHub

Nginx as load balancer

docker compose --file docker-compose-nginx.yml up --scale myapp=3 --detach

Nginx will listen to 8080 port and transfers the request to one of myapp's 80 port by load balancing using round-robin.

$ curl -sS http://localhost:8080
Hello from host: 7daed9e183ee

$ curl -sS http://localhost:8080
Hello from host: e2bcc4860c92

Traefik as load balancer

docker compose --file docker-compose-traefik.yml up --scale myapp=3 --detach

Traefik will listen to 8080 port and transfers the request to one of myapp's 80 port by load balancing using round-robin.

$ curl -sS http://localhost:8080
Hello from host: 7daed9e183ee

$ curl -sS http://localhost:8080
Hello from host: e2bcc4860c92

Benchmarking

Note: Increasing the number of containers serving a service, does not always lead to an increase in performance.

This is because performance depends not only on CPU speed, but also on a number of other factors, such as the number of threads (cores) that can be processed, RAM capacity, etc.

If the hardware cannot be changed, it is advisable to first measure the maximum access volume by benchmarking in order to understand the limits.

$ ab -V
This is ApacheBench, Version 2.3 <$Revision: 1903618 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

$ docker compose up --scale myapp=3 --detach
**snip**

$ curl -sS http://localhost:8080/
Hello from host: e2bcc4860c92


$ # Expect 100 users (-c=100) requesting 1 request at the same time (-n=100=100x1)
$ ab -n 100 -c 100 http://localhost:8080/
**snip**
Failed requests:        0
**snip**
Requests per second:    1608.18 [#/sec] (mean)
**snip**

$ # Expect 100 users (-c=100) requesting 10 request at the same time (-n=1000=100x10)
$ ab -n 1000 -c 100 http://localhost:8080/
**snip**
Failed requests:        0
**snip**
Requests per second:    1064.04 [#/sec] (mean)
**snip**

docker-compose-nginx.yml

services:
  myapp:
    build:
      context: https://github.com/KEINOS/imhost.git
    expose:
      - "80"
    restart: unless-stopped

  nginx:
    image: nginx:latest
    volumes:
      - ./nginx.conf:/etc/nginx/nginx.conf:ro
    ports:
      - "8080:8080"
    healthcheck:
      test: ["CMD", "service", "nginx", "status"]
      start_period: 15s
      interval: 5m
      timeout: 15s
      retries: 3
    restart: unless-stopped

docker-compose-traefik.yml

services:
  myapp:
    build:
      context: https://github.com/KEINOS/imhost.git
    expose:
      - "80"
    restart: unless-stopped
    labels:
      # Settings for Traefik (172.111.111.111 is the global IP of the host)
      - "traefik.enable=true"
      - "traefik.http.routers.myapp.rule=Host(`localhost`, `127.0.0.1`, `172.111.111.111`, `your.example.com`)"
      - "traefik.http.routers.myapp.entrypoints=web"

  traefik:
    image: traefik:latest
    command:
      - "--log.level=DEBUG"
      - "--api.insecure=false"
      - "--api.dashboard=false"
      - "--providers.docker=true"
      - "--providers.docker.exposedbydefault=false"
      - "--entrypoints.web.address=:80"
    ports:
      - "8080:80"
    volumes:
      - "/var/run/docker.sock:/var/run/docker.sock:ro"
    restart: unless-stopped

nginx.conf

user nginx;

worker_processes auto;

events {
    worker_connections 1024;
}

http {
    server {
        listen 8080;
        location / {
            proxy_pass http://myapp:80;
        }
    }
}