Docker Sync start script (only returns once initial sync is complete for all endpoints)

start-docker-sync-and-wait.sh

#!/bin/bash

DOCKER_SYNC_LOGFILE="/tmp/docker-sync.log"
DOCKER_SYNC_SCREEN_NAME="docker-sync"

function start_docker_sync_screen_session {
  # We start `docker-sync start` twice because it often updates some images on first run and when it does,
  # it exits successfully but asking for a `docker-sync clean` and then another `docker-sync start` run ¯\_(ツ)_/¯
  local cmd="docker-sync clean && docker-sync start && docker-sync clean && docker-sync start"
  screen -d -m -S ${DOCKER_SYNC_SCREEN_NAME} script -F ${DOCKER_SYNC_LOGFILE} bash -c "${cmd}"
}

function kill_docker_sync_screen_session {
  screen -dr ${DOCKER_SYNC_SCREEN_NAME} -X quit
}

function print_ids_of_ready_sync_containers {
  [[ ! -f ${DOCKER_SYNC_LOGFILE} ]] && return 0
  cat ${DOCKER_SYNC_LOGFILE} | grep "Connected \[//" | sed -nE "s|//($(hostname))//|//__HOST_NAME__//|p" | sed -nE "s|.*//([0-9a-f]+)//.*|\1|p" | sort | uniq
}

function print_names_of_ready_sync_containers {
  print_ids_of_ready_sync_containers | sed 's/^/-f id=/' | xargs docker ps --format '{{.Names}}' | sort | uniq
}

function wait_for_docker_sync {
  local expected_sync_services=$(docker-sync list | awk '{print $1}' | grep '.-sync$' | sort)

  trap kill_docker_sync_screen_session EXIT
  echo "Waiting for Docker Sync initial sync to be completed... (it may take up to a few minutes)"
  while [[ $(print_names_of_ready_sync_containers) != ${expected_sync_services} ]]; do
    sleep 10
  done
  trap - EXIT
}

if screen -ls | awk '{print $1}' | grep -q "^[0-9]\+.${DOCKER_SYNC_SCREEN_NAME}\$"; then
  echo "Docker Sync is already running"
else
  start_docker_sync_screen_session && wait_for_docker_sync \
    && echo "Docker Sync successfully started in background" \
    || echo "Failed to start Docker Sync in background"
fi