chore(docker): add tools for generating docker images

docker/wait-for.sh

@@ -0,0 +1,60 @@
+#!/bin/sh
+[ -n "$DEBUG" ] && set -x
+
+check_http() {
+  wget -T 1 -S -q -O - "$1" 2>&1 | head -1 |
+    head -1 | grep -E 'HTTP.+\s2\d{2}' >/dev/null 2>&1
+  return $?
+}
+
+check_tcp() {
+  host="$(echo "$1" | cut -d: -f1)"
+  port="$(echo "$1" | cut -d: -f2)"
+  if [ -z "${host}" ] || [ -z "${port}" ]; then
+    echo "TCP target ${1} is not in \"<host>:<port>\" format" >&2
+    exit 2
+  fi
+
+  nc -z -w1 "$host" "$port" >/dev/null 2>&1
+  return $?
+}
+
+wait_for() {
+  type="$1"
+  uri="$2"
+  timeout="${3:-30}"
+
+  seconds=0
+  while [ "$seconds" -lt "$timeout" ] && ! "check_${type}" "$uri"; do
+    if [ "$seconds" -lt "1" ]; then
+      printf "Waiting for %s  ." "$uri"
+    else
+      printf .
+    fi
+    seconds=$((seconds + 1))
+    sleep 1
+  done
+
+  if [ "$seconds" -lt "$timeout" ]; then
+    if [ "$seconds" -gt "0" ]; then
+      echo "  up!"
+    fi
+  else
+    echo "  FAIL"
+    echo "ERROR: unable to connect to: $uri" >&2
+    exit 1
+  fi
+}
+
+if [ -n "$WAIT_FOR_TARGETS" ]; then
+  uris="$(echo "$WAIT_FOR_TARGETS" | sed -e 's/\s+/\n/g' | uniq)"
+  for uri in $uris; do
+    if echo "$uri" | grep -E '^https?://.*' >/dev/null 2>&1; then
+      wait_for "http" "$uri" "$WAIT_FOR_TIMEOUT"
+    else
+      wait_for "tcp" "$uri" "$WAIT_FOR_TIMEOUT"
+    fi
+  done
+fi
+
+exec "$@"