preStop script for mongo replica set in kubernetes

preStop.sh

#!/usr/bin/env bash

PORT=27017
MONGO_LABEL=${TRACK}-mongo
LOGFILE="/postStart.log"
date > $LOGFILE

# Get the pods referenced by the Headless Service
function getPods() {
	curl -s -H "Authorization: Bearer $(cat /var/run/secrets/kubernetes.io/serviceaccount/token)" \
	--cacert /var/run/secrets/kubernetes.io/serviceaccount/ca.crt \
	https://${KUBERNETES_SERVICE_HOST}/api/v1/namespaces/${TRACK}/endpoints/${MONGO_LABEL} \
	| jq '.subsets[]? .addresses[]? .ip' \
	| awk -F\" '{print $2":'$PORT'"}'
}

# Check if the pod is part of a replica set, and output name if it is master
function replicaSetMaster() {
	OUTPUT=$(mongo $1 --quiet --eval "db.isMaster()['primary']")
	eval "$2=${OUTPUT}"
}

function reconfig() {
	echo "RECONFIGURING" >> $LOGFILE
	echo "cfg=rs.conf(); \
		healthy=rs.status().members.filter(function(d){return d.health>0;}).map(function(d){ return d.name;}); \
		cfg.members=cfg.members.filter(function(d){return healthy.indexOf(d.host) >=0;}); \
		rs.reconfig(cfg,{force:true}); \
		" | mongo $1 --quiet >> $LOGFILE
}

function removeMember() {
	echo "REMOVING $2 node from replicaSet" >> $LOGFILE
	mongo $1 --quiet --eval "rs.remove('${2}',{'force':true})"  >> $LOGFILE
}

function findMaster() {
	local PODS
	PODS=$(getPods)
	MASTER=""
	for POD in $PODS;
	do
		replicaSetMaster $POD M
		if [[ "$M" != "" ]];
		then
			MASTER=$M
		fi
	done
	echo "FOUND MASTER: $MASTER" >> $LOGFILE
}

# wait a bit for Service to register
sleep 10

THISNODE="$(hostname -i):${PORT}"
echo "MY IP: $THISNODE" >> $LOGFILE

# Get IPs of Pods in the cluster
# when first node, there won't be any as the pod is only registered by the Service once this hook has run
PODS=$(getPods)
echo "KUBERNETES PODS found: $PODS" >> $LOGFILE
# Find the master if there is one
findMaster

while [[ "$MASTER" == "" ]]; do
	sleep 2
	reconfig ${PODS[0]}
	findMaster;
done
removeMember $MASTER $THISNODE

exit 0