added to nginx the option to verify hostnames changes in ip. nginx open source doesn't resolve upstream servers after start

nginx/Dockerfile

@@ -1,7 +1,7 @@
 FROM centos:7
 COPY repo /etc/yum.repos.d/Nginx.repo
 RUN yum update -y
-RUN yum install -y nginx \
+RUN yum install -y nginx bind-utils\
   && yum clean all
 COPY docker-entrypoint.sh /
 RUN chmod +x /docker-entrypoint.sh

nginx/docker-entrypoint.sh

@@ -31,8 +31,58 @@ else
 	
 fi
 
+if [[ (! -z "${HOSTNAMESTOCHECK}" ) ]]; then
+	"$@" -c "/etc/nginx/nginx_tmp.conf" -g "daemon off;" &
+
+	declare -A HOSTNAMESIP
+	IFS="," read -a HOSTNAMESTOCHECKARRAY <<< "${HOSTNAMESTOCHECK}"
+	for HOST in "${HOSTNAMESTOCHECKARRAY[@]}"
+	do
+		HOSTIP=`dig +short $HOST`
+		HOSTIP=`echo "$HOSTIP" | tr ' ' '\n' | sort | tr '\n' ' '`
+		HOSTNAMESIP[$HOST]=$HOSTIP
+		echo IP FOR $HOST $HOSTIP
+	done
+
+	sleep 10
+	
+	while true
+	do
+		IPCHANGED=0
+		for HOST in "${HOSTNAMESTOCHECKARRAY[@]}"
+		do
+			NEWHOSTIP=`dig +short $HOST`
+			NEWHOSTIP=`echo "$NEWHOSTIP" | tr ' ' '\n' | sort | tr '\n' ' '`
+			OLDHOSTIP=${HOSTNAMESIP[$HOST]}
+			if [ "$NEWHOSTIP" != "$OLDHOSTIP" ]; then
+				if [ "$IPCHANGED" = 0 ]; then
+					IPCHANGED=1
+				fi
+				HOSTNAMESIP[$HOST]=$NEWHOSTIP
+				echo NEW IP FOR $HOST $NEWHOSTIP
+			fi
+		done
+		if [ "$IPCHANGED" = 1 ]; then
+			if [[ `ps -acx|grep nginx|wc -l` > 0 ]]; then
+				echo "RELOADING NGINX"
+				nginx -s reload
+			else
+				echo "RESTARTING NGINX"
+				"$@" -c "/etc/nginx/nginx_tmp.conf" -g "daemon off;" &
+			fi
+		fi
+		sleep 10
+	done
+
+else
+
 	"$@" -c "/etc/nginx/nginx_tmp.conf" -g "daemon off;"
 
+fi
+
+
+
+