chore(script): Add a help script to test clustering with docker

scripts/start-two-nodes-in-docker.sh

@@ -0,0 +1,66 @@
+#!/bin/bash
+
+set -euo pipefail
+
+## This script takes the first argument as docker iamge name,
+## starts two containers running with the built code mount
+## into docker containers.
+##
+## NOTE: containers are not instructed to rebuild emqx,
+##       Please use a docker image which is compatible with
+##       the docker host.
+##
+## EMQX can only start with longname (https://erlang.org/doc/reference_manual/distributed.html)
+## The host name part of EMQX's node name has to be static, this means we should either
+## pre-assign static IP for containers, or ensure containers can communiate with each other by name
+## this is why a docker network is created, and the containers's names have a dot.
+
+# ensure dir
+cd -P -- "$(dirname -- "$0")/.."
+
+IMAGE="${1}"
+PROJ_DIR="$(pwd)"
+
+NET='emqx.io'
+NODE1="node1.$NET"
+NODE2="node2.$NET"
+COOKIE='this-is-a-secret'
+
+## clean up
+docker rm -f "$NODE1" >/dev/null 2>&1 || true
+docker rm -f "$NODE2" >/dev/null 2>&1 || true
+docker network rm "$NET" >/dev/null 2>&1 || true
+
+docker network create "$NET"
+
+docker run -d -t --restart=always --name "$NODE1" \
+  --net "$NET" \
+  -e EMQX_NODE_NAME="emqx@$NODE1" \
+  -e EMQX_NODE_COOKIE="$COOKIE" \
+  -e WAIT_FOR_ERLANG=60 \
+  -p 18083:18083 \
+  -v $PROJ_DIR/_build/emqx/rel/emqx:/built \
+  $IMAGE sh -c 'cp -r /built /emqx && /emqx/bin/emqx console'
+
+docker run -d -t --restart=always --name "$NODE2" \
+  --net "$NET" \
+  -e EMQX_NODE_NAME="emqx@$NODE2" \
+  -e EMQX_NODE_COOKIE="$COOKIE" \
+  -e WAIT_FOR_ERLANG=60 \
+  -p 18084:18083 \
+  -v $PROJ_DIR/_build/emqx/rel/emqx:/built \
+  $IMAGE sh -c 'cp -r /built /emqx && /emqx/bin/emqx console'
+
+wait (){
+  container="$1"
+  while ! docker exec "$container" /emqx/bin/emqx_ctl status >/dev/null 2>&1; do
+    echo -n '.'
+    sleep 1
+  done
+}
+
+wait $NODE1
+wait $NODE2
+echo
+
+docker exec $NODE1 /emqx/bin/emqx_ctl cluster join "emqx@$NODE2"