Add an example for running rethinkdb cluster on k8s

examples/rethinkdb/image/run.sh

@@ -0,0 +1,23 @@
+#!/bin/bash
+
+set -o pipefail
+
+IP=""
+if [[ -n "${KUBERNETES_RO_SERVICE_HOST}" ]]; then
+
+  : ${NAMESPACE:=rethinkdb}
+  # try to pick up first different ip from endpoints
+  MYHOST=$(ip addr | grep 'state UP' -A2 | tail -n1 | awk '{print $2}' | cut -f1  -d'/')
+  URL="${KUBERNETES_RO_SERVICE_HOST}/api/v1beta1/endpoints/rethinkdb-driver?namespace=${NAMESPACE}"
+  IP=$(curl -s ${URL} | jq -s -r --arg h "${MYHOST}" '.[0].endpoints | [ .[]? | split(":") ] | map(select(.[0] != $h)) | .[0][0]') || exit 1
+  [[ "${IP}" == null ]] && IP=""
+fi
+
+if [[ -n "${IP}" ]]; then
+  ENDPOINT="${IP}:29015"
+  echo "Join to ${ENDPOINT}"
+  exec rethinkdb --bind all  --join ${ENDPOINT}
+else
+  echo "Start single instance"
+  exec rethinkdb --bind all
+fi