Wait for a port at remote site to be opened. Same as https://github.com/Eficode/wait-for but with options to be silent and an exponential backoff when waiting.

wait-for.sh

#!/bin/sh

# This comes from : https://github.com/Eficode/wait-for

# The MIT License (MIT)
#
# Copyright (c) 2017 Eficode Oy
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.


WAITFOR_TIMEOUT=${WAITFOR_TIMEOUT:-120}
WAITFOR_QUIET=${WAITFOR_QUIET:-0}
WAITFOR_VERBOSE=${WAITFOR_VERBOSE:-0}
WAITFOR_WAIT=${WAITFOR_WAIT:-1}
WAITFOR_SPEED=${WAITFOR_SPEED:-2}
WAITFOR_BACKOFF=${WAITFOR_BACKOFF:-15}
WAITFOR_HOST=${WAITFOR_HOST:-}
WAITFOR_PORT=${WAITFOR_PORT:-}

echoerr() {
  if [ "$WAITFOR_QUIET" -ne 1 ]; then printf "%s\n" "$*" 1>&2; fi
}

usage() {
  exitcode="$1"
  cat << USAGE >&2
Usage:
  $cmdname host:port [-t timeout] [-- command args]
  -v | --verbose                      Be more verbose when waiting
  -q | --quiet                        Do not output any status messages
  -t TIMEOUT | --timeout=timeout      Timeout in seconds, zero for no timeout
  -w WAIT | --wait=seconds            Number of seconds to wait between attempts
  -b BACKOFF | --backoff=seconds      Maximum number of seconds to wait for exponential backoff
  -s SPEED | --speed=float            Seconds multiplier when exponential backoff.
  -- COMMAND ARGS                     Execute command with args after the test finishes
USAGE
  exit "$exitcode"
}

wait_once() {
  NC=`which nc`
  BASH=`which bash`
  if [ -n "$NC" ]; then
    if [ "$WAITFOR_VERBOSE" = "1" -a "$WAITFOR_QUIET" = "0" ]; then
        echo "Waiting for ${WAITFOR_HOST}:${WAITFOR_PORT} with ${NC}..." 1>&2
    fi
    ${NC} -z -w 5 "$WAITFOR_HOST" "$WAITFOR_PORT" > /dev/null 2>&1
  elif [ -n "$BASH" ]; then
    if [ "$WAITFOR_VERBOSE" = "1" -a "$WAITFOR_QUIET" = "0" ]; then
        echo "Waiting for ${WAITFOR_HOST}:${WAITFOR_PORT} with ${BASH}..." 1>&2
    fi
    timeout 5 ${BASH} -c "echo >/dev/tcp/${WAITFOR_HOST}/${WAITFOR_PORT}" >/dev/null 2>&1
  else
    echo "CANNOT test connection to ${WAITFOR_HOST}:${WAITFOR_PORT}!"
    exit 0
  fi

  result=$?
  if [ $result -eq 0 ] ; then
    if [ $# -gt 0 ] ; then
      if [ "$WAITFOR_VERBOSE" = "1" -a "$WAITFOR_QUIET" = "0" ]; then
        echo "Connection to ${WAITFOR_HOST}:${WAITFOR_PORT} established" 1>&2
      fi
      exec "$@"
    fi
    exit 0
  fi
  sleep ${WAITFOR_WAIT}
}

adjust() {
  if [ "${WAITFOR_SPEED}" -ne "1" ]; then
    WAITFOR_WAIT=$(awk "BEGIN{print int($WAITFOR_WAIT * $WAITFOR_SPEED)}")
    if [ "${WAITFOR_WAIT}" -gt "${WAITFOR_BACKOFF}" ]; then
      WAITFOR_WAIT="${WAITFOR_BACKOFF}"
    fi
  fi
}

wait_for() {
  if [ "$WAITFOR_TIMEOUT" = "" -o "$WAITFOR_TIMEOUT" -le "0" ]; then
    while true; do
      wait_once "$@"
      adjust
    done
  else
    waited=0
    while [ "$waited" -lt "${WAITFOR_TIMEOUT}" ]; do
      wait_once "$@"
      waited=$(expr $waited + ${WAITFOR_WAIT})
      adjust
    done
  fi
  echo "Operation timed out" >&2
  exit 1
}

while [ $# -gt 0 ]
do
  case "$1" in
    *:* )
      WAITFOR_HOST=$(printf "%s\n" "$1"| cut -d : -f 1)
      WAITFOR_PORT=$(printf "%s\n" "$1"| cut -d : -f 2)
      shift 1
      ;;
    -q | --quiet)
      WAITFOR_QUIET=1
      shift 1
      ;;
    -v | --verbose)
      WAITFOR_VERBOSE=1
      shift 1
      ;;
    -t | --timeout)
      WAITFOR_TIMEOUT="$2"
      if [ "$WAITFOR_TIMEOUT" = "" ]; then break; fi
      shift 2
      ;;
    --timeout=*)
      WAITFOR_TIMEOUT="${1#*=}"
      shift 1
      ;;
    -w | --wait)
      WAITFOR_WAIT="$2"
      shift 2
      ;;
    --wait=*)
      WAITFOR_WAIT="${1#*=}"
      shift 1
      ;;
    -b | --backoff)
      WAITFOR_BACKOFF="$2"
      shift 2
      ;;
    --backoff=*)
      WAITFOR_BACKOFF="${1#*=}"
      shift 1
      ;;
    -s | --speed)
      WAITFOR_SPEED="$2"
      shift 2
      ;;
    --speed=*)
      WAITFOR_SPEED="${1#*=}"
      shift 1
      ;;
    --)
      shift
      break
      ;;
    --help)
      usage 0
      ;;
    *)
      echoerr "Unknown argument: $1"
      usage 1
      ;;
  esac
done

if [ "$WAITFOR_HOST" = "" -o "$WAITFOR_PORT" = "" ]; then
  echoerr "Error: you need to provide a host and port to test."
  usage 2
fi

wait_for "$@"