A simple script to wait for a service's port to open.

wait-for-service.sh

#!/usr/bin/env sh

WAIT_FOR_HOST=$1
WAIT_FOR_PORT=$2

while ! nc -z "$WAIT_FOR_HOST" "$WAIT_FOR_PORT"; do
  sleep 0.3
  echo "INFO  [wait-for] Checking $WAIT_FOR_HOST:$WAIT_FOR_PORT"
done

echo "INFO  [wait-for] Connected $WAIT_FOR_HOST:$WAIT_FOR_PORT"