Connect to remote erlang node with remote iex session (eg over k8s port-forwarding), and start observer on it

iex-observe.sh

#!/bin/bash
# This script provides easy way to debug remote Erlang nodes that is running in a kubernetes cluster.
# Usage: ./erl-observe.sh -l app=my_all -n default -c erlang_cookie
#
# Don't forget to include `:runtime_tools` in your mix.exs application dependencies.
set -e

# Trap exit so we can try to kill proxies that has stuck in background
function cleanup() {
	echo " - Starting local epmd again"
	epmd -daemon &>/dev/null

	echo " - Stopping kubectl proxy."
	kill $! &>/dev/null
}
trap cleanup EXIT

# Read configuration from CLI
while getopts "n:l:u:c:e:" opt; do
	case "$opt" in
	n)
		K8S_NAMESPACE="--namespace=${OPTARG}"
		;;
	l)
		K8S_SELECTOR=${OPTARG}
		;;
	u)
		ERL_USER=${OPTARG}
		;;
	c)
		ERL_COOKIE=${OPTARG}
		;;
	e)
		EPMD_PATH=${OPTARG}
		;;
	esac
done

if [ ! $EPMD_PATH ]; then
	echo "[W] Setting epmd path to 'epmd'"
	EPMD_PATH=epmd
fi

# Required part of config
if [ ! $K8S_SELECTOR ]; then
	echo "[E] You need to specify Kubernetes selector with '-l' option."
	exit 1
fi

echo " - Selecting pod with '-l ${K8S_SELECTOR} ${K8S_NAMESPACE:-default}' selector."
POD_NAME=$(kubectl get pods -l ${K8S_SELECTOR} ${K8S_NAMESPACE} -o jsonpath='{.items[0].metadata.name}')

echo " - Resolving Erlang node port on a pod '${POD_NAME}'."
EPMD_OUTPUT=$(echo ${POD_NAME} | xargs -o -I my_pod kubectl exec my_pod ${K8S_NAMESPACE} -i -t -- ${EPMD_PATH} -names | tail -n 1)

echo " - Got output from epmd: "
echo " - ${EPMD_OUTPUT}"
eval 'EPMD_OUTPUT=($EPMD_OUTPUT)'

# By default, cookie is the same as node name
if [ ! $ERL_COOKIE ]; then
	ERL_COOKIE=${EPMD_OUTPUT[1]}
fi

# By default, user is debug
if [ ! $ERL_USER ]; then
	ERL_USER="debug"
fi

# Strip newlines from last element of output
OTP_PORT=${EPMD_OUTPUT[4]//[$'\t\r\n ']/}

echo " - Connecting on port ${OTP_PORT} as user '${ERL_USER}' with cookie '${ERL_COOKIE}'."

# Kill epmd on local node to free 4369 port
killall epmd || true

# Replace it with remote nodes epmd and proxy remove erlang app port
echo "kubectl port-forward ${POD_NAME} ${K8S_NAMESPACE} 4369 ${OTP_PORT}"

kubectl port-forward $POD_NAME $K8S_NAMESPACE 4369 $OTP_PORT &>/dev/null &
sleep 1

# Run observer in hidden mode to don't heart clusters health
# erl -name [email protected] -setcookie $ERL_COOKIE -hidden -run observer
iex --name [email protected] --hidden --cookie $ERL_COOKIE -e ':observer.start()'