HAProxy in Docker with logging to stdout (because it's hard to figure out)

docker-compose.yml

# The trick here is to run syslogd, writing output to the stdout of PID1, which Docker daemon captures
# This may be a useful trick with other executables as well that can only write to syslog

version: '3'

services:
  haproxy:
    image: haproxy:1.9-alpine
    entrypoint: ''
    command: sh -c 'syslogd -O /proc/1/fd/1; /docker-entrypoint.sh haproxy -f /etc/haproxy/haproxy.cfg'
    ports:
      - 80:80
    volumes:
      - .:/etc/haproxy:ro

haproxy.cfg

# Include this in your haproxy config file
# It will log to /dev/log that syslogd provides

defaults
    log /dev/log local0
    mode http
    option httplog