diff --git a/Dockerfile b/Dockerfile
index e17409a..b6fe61d 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,7 +1,16 @@
-FROM postgres:9.6
-MAINTAINER Daniel Dent (https://www.danieldent.com)
+FROM postgres:15.0
+
+RUN apt-get update -y
+RUN apt-get install -y iputils-ping
+
 ENV PG_MAX_WAL_SENDERS 8
-ENV PG_WAL_KEEP_SEGMENTS 8
+ENV PG_WAL_KEEP_SIZE 128
+
 COPY setup-replication.sh /docker-entrypoint-initdb.d/
-COPY docker-entrypoint.sh /docker-entrypoint.sh
-RUN chmod +x /docker-entrypoint-initdb.d/setup-replication.sh /docker-entrypoint.sh
+COPY docker-entrypoint.sh /usr/local/bin/docker-entrypoint.sh
+COPY standby.signal /tmp/standby.signal
+
+RUN chmod +x /docker-entrypoint-initdb.d/setup-replication.sh /usr/local/bin/docker-entrypoint.sh
+
+## debug
+# ENTRYPOINT ["tail", "-f", "/dev/null"]
\ No newline at end of file
diff --git a/README.md b/README.md
index 09a348e..3e728f5 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-# Postgres 9.6 Dockerized w/ Replication
+# Postgres 15.0 Dockerized w/ Replication
 
 Master/Slave Postgres Replication in 30 seconds.
 
@@ -14,6 +14,3 @@ Master/Slave Postgres Replication in 30 seconds.
    * No additional replication user is setup - the postgres admin user is used. This means the superuser credentials must be identical on the master and all slaves.
    * setup-replication.sh is only executed when a container's data volume is first initialized.
    * REPLICATE_FROM environment variable is only used during container initialization - if the master changes after the database has been initialized, you'll need to manually adjust the recovery.conf file in the slave containers' data volume.
-   * Configuration:
-     * PG_MAX_WAL_SENDERS 8 - Maximum number of slaves
-     * PG_WAL_KEEP_SEGMENTS 32 - See http://www.postgresql.org/docs/9.6/static/runtime-config-replication.html
diff --git a/docker-compose.yml b/docker-compose.yml
index 81a66da..858a719 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -1,32 +1,33 @@
-
-version: '2'
+version: "3.8"
 
 services:
   pg-master:
-    build: '.'
-    image: 'danieldent/postgres-replication'
-    restart: 'always'
+    build: .
+    restart: always
+    ports:
+      - "5432:5432"
     environment:
-      POSTGRES_USER: 'postgres'
-      POSTGRES_PASSWORD: 'postgres'
-      PGDATA: '/var/lib/postgresql/data/pgdata'
+      - POSTGRES_DB=test
+      - POSTGRES_USER=postgres
+      - POSTGRES_PASSWORD=postgres
+      - PGDATA=/var/lib/postgresql/data/pgdata
+      #- REPLICATE_FROM=pg-slave #only after pg-slave get promoted
     volumes:
-     - '/var/lib/postgresql/data'
-    expose:
-     - '5432'
+      - /var/lib/postgresql/data
 
+  # #Promote to master `select pg_promote(true,60);`
   pg-slave:
-    build: '.'
-    image: 'danieldent/postgres-replication'
-    restart: 'always'
+    build: .
+    restart: always
+    ports:
+      - "2432:5432"
     environment:
-      POSTGRES_USER: 'postgres'
-      POSTGRES_PASSWORD: 'postgres'
-      PGDATA: '/var/lib/postgresql/data/pgdata'
-      REPLICATE_FROM: 'pg-master'
+      - POSTGRES_DB=test
+      - POSTGRES_USER=postgres
+      - POSTGRES_PASSWORD=postgres
+      - PGDATA=/var/lib/postgresql/data/pgdata
+      - REPLICATE_FROM=pg-master
+    depends_on:
+      - "pg-master"
     volumes:
-     - '/var/lib/postgresql/data'
-    expose:
-     - '5432'
-    links:
-     - 'pg-master'
+      - /var/lib/postgresql/data
diff --git a/docker-entrypoint.sh b/docker-entrypoint.sh
index f290efb..b8cd750 100755
--- a/docker-entrypoint.sh
+++ b/docker-entrypoint.sh
@@ -34,18 +34,18 @@ if [ "$1" = 'postgres' ]; then
 	# look specifically for PG_VERSION, as it is expected in the DB dir
 	if [ ! -s "$PGDATA/PG_VERSION" ]; then
 	    if [ "x$REPLICATE_FROM" == "x" ]; then
-		eval "gosu postgres initdb $POSTGRES_INITDB_ARGS"
+			eval "gosu postgres initdb $POSTGRES_INITDB_ARGS"
 	    else
-            	until ping -c 1 -W 1 ${REPLICATE_FROM}
-            	do
-                	echo "Waiting for master to ping..."
-                	sleep 1s
-            	done
-            	until gosu postgres pg_basebackup -h ${REPLICATE_FROM} -D ${PGDATA} -U ${POSTGRES_USER} -vP -w
-            	do
-                	echo "Waiting for master to connect..."
-                	sleep 1s
-            	done
+			until ping -c 1 -W 1 ${REPLICATE_FROM}
+			do
+				echo "Waiting for master to ping..."
+				sleep 1s
+			done
+			until gosu postgres pg_basebackup -h ${REPLICATE_FROM} -D ${PGDATA} -U ${POSTGRES_USER} -vP -w
+			do
+				echo "Waiting for master to connect..."
+				sleep 1s
+			done
 	    fi
 
 		# check password first so we can output the warning before postgres
@@ -73,39 +73,39 @@ if [ "$1" = 'postgres' ]; then
 			authMethod=trust
 		fi
 
-		if [ "x$REPLICATE_FROM" == "x" ]; then
-
 		{ echo; echo "host replication all 0.0.0.0/0 $authMethod"; } | gosu postgres tee -a "$PGDATA/pg_hba.conf" > /dev/null
 		{ echo; echo "host all all 0.0.0.0/0 $authMethod"; } | gosu postgres tee -a "$PGDATA/pg_hba.conf" > /dev/null
 
-		# internal start of server in order to allow set-up using psql-client		
-		# does not listen on external TCP/IP and waits until start finishes
-		gosu postgres pg_ctl -D "$PGDATA" \
-			-o "-c listen_addresses='localhost'" \
-			-w start
-
-		: ${POSTGRES_USER:=postgres}
-		: ${POSTGRES_DB:=$POSTGRES_USER}
-		export POSTGRES_USER POSTGRES_DB
-
-		psql=( psql -v ON_ERROR_STOP=1 )
+		if [ "x$REPLICATE_FROM" == "x" ]; then
 
-		if [ "$POSTGRES_DB" != 'postgres' ]; then
+			# internal start of server in order to allow set-up using psql-client		
+			# does not listen on external TCP/IP and waits until start finishes
+			gosu postgres pg_ctl -D "$PGDATA" \
+				-o "-c listen_addresses='localhost'" \
+				-w start
+
+			: ${POSTGRES_USER:=postgres}
+			: ${POSTGRES_DB:=$POSTGRES_USER}
+			export POSTGRES_USER POSTGRES_DB
+
+			psql=( psql -v ON_ERROR_STOP=1 )
+
+			if [ "$POSTGRES_DB" != 'postgres' ]; then
+				"${psql[@]}" --username postgres <<-EOSQL
+					CREATE DATABASE "$POSTGRES_DB" ;
+				EOSQL
+				echo
+			fi
+
+			if [ "$POSTGRES_USER" = 'postgres' ]; then
+				op='ALTER'
+			else
+				op='CREATE'
+			fi
 			"${psql[@]}" --username postgres <<-EOSQL
-				CREATE DATABASE "$POSTGRES_DB" ;
+				$op USER "$POSTGRES_USER" WITH SUPERUSER $pass ;
 			EOSQL
 			echo
-		fi
-
-		if [ "$POSTGRES_USER" = 'postgres' ]; then
-			op='ALTER'
-		else
-			op='CREATE'
-		fi
-		"${psql[@]}" --username postgres <<-EOSQL
-			$op USER "$POSTGRES_USER" WITH SUPERUSER $pass ;
-		EOSQL
-		echo
 		
 		fi
 
@@ -122,9 +122,9 @@ if [ "$1" = 'postgres' ]; then
 			echo
 		done
 
-	if [ "x$REPLICATE_FROM" == "x" ]; then
-		gosu postgres pg_ctl -D "$PGDATA" -m fast -w stop
-	fi
+		if [ "x$REPLICATE_FROM" == "x" ]; then
+			gosu postgres pg_ctl -D "$PGDATA" -m fast -w stop
+		fi
 
 		echo
 		echo 'PostgreSQL init process complete; ready for start up.'
diff --git a/setup-replication.sh b/setup-replication.sh
index 460c548..a81ac33 100755
--- a/setup-replication.sh
+++ b/setup-replication.sh
@@ -3,20 +3,23 @@
 if [ "x$REPLICATE_FROM" == "x" ]; then
 
 cat >> ${PGDATA}/postgresql.conf <<EOF
+listen_addresses='*'
 wal_level = hot_standby
 max_wal_senders = $PG_MAX_WAL_SENDERS
-wal_keep_segments = $PG_WAL_KEEP_SEGMENTS
+wal_keep_size = $PG_WAL_KEEP_SIZE
 hot_standby = on
 EOF
 
 else
 
-cat > ${PGDATA}/recovery.conf <<EOF
-standby_mode = on
+cat > ${PGDATA}/postgresql.conf <<EOF
+listen_addresses='*'
+wal_level = hot_standby
+max_wal_senders = $PG_MAX_WAL_SENDERS
+wal_keep_size = $PG_WAL_KEEP_SIZE
+hot_standby = on
 primary_conninfo = 'host=${REPLICATE_FROM} port=5432 user=${POSTGRES_USER} password=${POSTGRES_PASSWORD}'
-trigger_file = '/tmp/touch_me_to_promote_to_me_master'
 EOF
-chown postgres ${PGDATA}/recovery.conf
-chmod 600 ${PGDATA}/recovery.conf
+cp /tmp/standby.signal ${PGDATA}/standby.signal
 
 fi
diff --git a/standby.signal b/standby.signal
new file mode 100644
index 0000000..e69de29