running application and DB using docker-compose.yml is tricky, because app will not wait for DB to be fully up and read to accept connections (docker-compose.yml only deals with dependencies). This function can be part of application entrypoint script, it waits up to 30 seconds for postgres to start. It uses pg_isready (works even without passwo…

wait-for-it postgres style

function pg_ready() 
{

waitTime=30 # keep trying for x seconds
n=0

until [ $n -ge $waitTime ]; do
  # please note pg_isready does not care about username/dbname
  # you can add correct values if you want to avoid errors in PG log
  pg_isready --host=$DB_HOST --port=$DB_PORT && break
  n=$[$n+1]
  sleep 1;
done

}



if pg_ready ; then 
  echo "INFO: WHIIIIII let start the app."
else
  echo "ERROR: Database $$DB_HOST:$DB_PORT not found."
fi