diff --git a/plugins/README.md b/plugins/README.md
index 27c7430e..94f75027 100644
--- a/plugins/README.md
+++ b/plugins/README.md
@@ -16,6 +16,13 @@ This is an **example** plugin that demonstrates a basic authentication callback
 that allows clients based on their IP address. Password based authentication is
 preferred over this very simple type of access control.
 
+## Examples / Client lifetime stats
+This is an **example** plugin that collects counts of how long client sessions
+last, in different time buckets of 0, 1, 2, 5, 10, 20, 50, 100, 200, 500, 1k,
+2k, 5k, 10k, 20k, 50k, 100k, 200k, 500k, 1M, 2M, 5M, 10M, 20M, 50M, 100M, 200M,
+500M seconds. It periodically publishes the counts at
+`$SYS/broker/client/lifetimes/<bucket>`.
+
 ## Examples / Client properties
 This is an **example** plugin that demonstrates some of the functions for
 retrieving client information such as client id and username.
@@ -56,6 +63,12 @@ This plugin adds the text string "hello " to the beginning of each payload, so
 with anything other than simple plain text messages it will corrupt the payload
 contents.
 
+## Examples / Payload size stats
+This is an **example** plugin that collects counts of payload message sizes, in
+time buckets of 0, 1, 2, 5, 10, 20, 50, 100, 200, 500, 1k, 2k, 5k, 10k, 20k,
+50k, 100k, 200k, 500k, 1M, 2M, 5M, 10M, 20M, 50M, 100M, 200M, 500M bytes. It
+periodically publishes the counts at `$SYS/broker/publish/sizes/<bucket>`.
+
 ## Examples / Print IP on publish
 This is an **example** plugin that prints out client ID and IP address of any
 client that publishes on a particular topic.
diff --git a/plugins/examples/CMakeLists.txt b/plugins/examples/CMakeLists.txt
index 4c01a2a0..6913427e 100644
--- a/plugins/examples/CMakeLists.txt
+++ b/plugins/examples/CMakeLists.txt
@@ -1,5 +1,6 @@
 if(NOT WIN32)
 	add_subdirectory(add-properties)
+	add_subdirectory(client-lifetime-stats)
 	add_subdirectory(message-timestamp)
 endif()
 add_subdirectory(auth-by-ip)
@@ -8,5 +9,6 @@ add_subdirectory(connection-state)
 add_subdirectory(delayed-auth)
 add_subdirectory(force-retain)
 add_subdirectory(payload-modification)
+add_subdirectory(payload-size-stats)
 add_subdirectory(print-ip-on-publish)
 add_subdirectory(topic-modification)
diff --git a/plugins/examples/Makefile b/plugins/examples/Makefile
index 59bb6c40..84da6435 100644
--- a/plugins/examples/Makefile
+++ b/plugins/examples/Makefile
@@ -1,12 +1,14 @@
 DIRS= \
 		add-properties \
 		auth-by-ip \
+		client-lifetime-stats \
 		client-properties \
 		connection-state \
 		delayed-auth \
 		force-retain \
 		message-timestamp \
 		payload-modification \
+		payload-size-stats \
 		print-ip-on-publish \
 		topic-modification \
 		wildcard-temp
diff --git a/plugins/examples/client-lifetime-stats/CMakeLists.txt b/plugins/examples/client-lifetime-stats/CMakeLists.txt
new file mode 100644
index 00000000..80459a0b
--- /dev/null
+++ b/plugins/examples/client-lifetime-stats/CMakeLists.txt
@@ -0,0 +1,27 @@
+set (PLUGIN_NAME mosquitto_client_lifetime_stats)
+
+add_library(${PLUGIN_NAME} MODULE
+	${PLUGIN_NAME}.c
+)
+
+target_include_directories(${PLUGIN_NAME} PRIVATE
+	"${OPENSSL_INCLUDE_DIR}"
+	"${STDBOOL_H_PATH}"
+	"${STDINT_H_PATH}"
+	"${mosquitto_SOURCE_DIR}"
+	"${mosquitto_SOURCE_DIR}/deps"
+	"${mosquitto_SOURCE_DIR}/include"
+)
+
+link_directories(${mosquitto_SOURCE_DIR})
+
+set_target_properties(${PLUGIN_NAME} PROPERTIES
+	PREFIX ""
+	POSITION_INDEPENDENT_CODE 1
+)
+if(WIN32)
+	target_link_libraries(${PLUGIN_NAME} mosquitto)
+endif()
+
+# Don't install, these are example plugins only.
+#install(TARGETS ${PLUGIN_NAME} RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}" LIBRARY DESTINATION "${CMAKE_INSTALL_LIBDIR}")
diff --git a/plugins/examples/client-lifetime-stats/Makefile b/plugins/examples/client-lifetime-stats/Makefile
new file mode 100644
index 00000000..95da6df2
--- /dev/null
+++ b/plugins/examples/client-lifetime-stats/Makefile
@@ -0,0 +1,28 @@
+include ../../../config.mk
+
+.PHONY : all binary check clean reallyclean test install uninstall
+
+PLUGIN_NAME=mosquitto_client_lifetime_stats
+PLUGIN_CFLAGS+=-I../../../include -I../../../ -I../../../deps
+
+all : binary
+
+binary : ${PLUGIN_NAME}.so
+
+${PLUGIN_NAME}.so : ${PLUGIN_NAME}.c
+	$(CROSS_COMPILE)$(CC) $(PLUGIN_CPPFLAGS) $(PLUGIN_CFLAGS) $(PLUGIN_LDFLAGS) -fPIC -shared $< -o $@
+
+reallyclean : clean
+clean:
+	-rm -f *.o ${PLUGIN_NAME}.so *.gcda *.gcno
+
+check: test
+test:
+
+install: ${PLUGIN_NAME}.so
+	# Don't install, these are examples only.
+	$(INSTALL) -d "${DESTDIR}$(libdir)"
+	$(INSTALL) ${STRIP_OPTS} ${PLUGIN_NAME}.so "${DESTDIR}${libdir}/${PLUGIN_NAME}.so"
+
+uninstall :
+	-rm -f "${DESTDIR}${libdir}/${PLUGIN_NAME}.so"
diff --git a/plugins/examples/client-lifetime-stats/mosquitto_client_lifetime_stats.c b/plugins/examples/client-lifetime-stats/mosquitto_client_lifetime_stats.c
new file mode 100644
index 00000000..aeb6b2be
--- /dev/null
+++ b/plugins/examples/client-lifetime-stats/mosquitto_client_lifetime_stats.c
@@ -0,0 +1,197 @@
+/*
+Copyright (c) 2021 Roger Light <roger@atchoo.org>
+
+All rights reserved. This program and the accompanying materials
+are made available under the terms of the Eclipse Public License 2.0
+and Eclipse Distribution License v1.0 which accompany this distribution.
+
+The Eclipse Public License is available at
+   https://www.eclipse.org/legal/epl-2.0/
+and the Eclipse Distribution License is available at
+  http://www.eclipse.org/org/documents/edl-v10.php.
+
+SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
+
+Contributors:
+   Roger Light - initial implementation and documentation.
+*/
+
+/*
+ * Publish statistics on client session lifetimes.
+ *
+ * Compile with:
+ *   gcc -I<path to mosquitto-repo/include> -fPIC -shared mosquitto_client_lifetime_stats.c -o mosquitto_client_lifetime_stats.so
+ *
+ * Use in config with:
+ *
+ *   plugin /path/to/mosquitto_client_lifetime_stats.so
+ *
+ * Note that this only works on Mosquitto 2.0 or later.
+ */
+#include "config.h"
+
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <time.h>
+#include <uthash.h>
+
+#include "mosquitto_broker.h"
+#include "mosquitto_plugin.h"
+#include "mosquitto.h"
+#include "mqtt_protocol.h"
+
+MOSQUITTO_PLUGIN_DECLARE_VERSION(5);
+
+static mosquitto_plugin_id_t *mosq_pid = NULL;
+
+struct lifetime_s{
+	UT_hash_handle hh;
+	char *id;
+	time_t connect;
+};
+struct lifetime_s *local_lifetimes = NULL;
+
+#define LIFETIME_COUNT 28
+static const char *lifetime_strs[LIFETIME_COUNT] = {
+	"0",
+	"1", "2", "5",
+	"10", "20", "50",
+	"100", "200", "500",
+	"1k", "2k", "5k",
+	"10k", "20k", "50k",
+	"100k", "200k", "500k",
+	"1M", "2M", "5M",
+	"10M", "20M", "50M",
+	"100M", "200M", "500M"
+};
+
+static uint32_t lifetime_values[LIFETIME_COUNT] = {
+	0,
+	1, 2, 5,
+	10, 20, 50,
+	100, 200, 500,
+	1000, 2000, 5000,
+	10000, 20000, 50000,
+	100000, 200000, 500000,
+	1000000, 2000000, 5000000,
+	10000000, 20000000, 50000000,
+	100000000, 200000000, 500000000
+};
+
+static long lifetime_counts[LIFETIME_COUNT];
+static long last_lifetime_counts[LIFETIME_COUNT];
+static time_t last_report = 0;
+
+
+static int callback_tick(int event, void *event_data, void *userdata)
+{
+	struct timespec ts;
+	char topic[40];
+	char payload[40];
+	int slen;
+	int i;
+
+	UNUSED(event);
+	UNUSED(event_data);
+	UNUSED(userdata);
+
+	clock_gettime(CLOCK_REALTIME, &ts);
+	if(last_report + 10 < ts.tv_sec){
+		last_report = ts.tv_sec;
+
+		for(i=0; i<LIFETIME_COUNT; i++){
+			if(lifetime_counts[i] != last_lifetime_counts[i]){
+				snprintf(topic, sizeof(topic), "$SYS/broker/client/lifetimes/%s", lifetime_strs[i]);
+				slen = snprintf(payload, sizeof(payload), "%ld", lifetime_counts[i]);
+				mosquitto_broker_publish_copy(NULL, topic, slen, payload, 0, 1, NULL);
+				last_lifetime_counts[i] = lifetime_counts[i];
+			}
+		}
+	}
+
+	return MOSQ_ERR_SUCCESS;
+}
+
+
+static int callback_connect(int event, void *event_data, void *userdata)
+{
+	struct mosquitto_evt_connect *ed = event_data;
+	const char *id;
+	struct lifetime_s *client;
+
+	UNUSED(event);
+	UNUSED(userdata);
+
+	id = mosquitto_client_id(ed->client);
+	if(id){
+		HASH_FIND(hh, local_lifetimes, id, strlen(id), client);
+		if(!client){
+			client = malloc(sizeof(struct lifetime_s));
+			if(client == NULL){
+				return MOSQ_ERR_SUCCESS;
+			}
+			client->id = strdup(id);
+			if(client->id == NULL){
+				free(client);
+				return MOSQ_ERR_SUCCESS;
+			}
+			client->connect = time(NULL);
+			HASH_ADD_KEYPTR(hh, local_lifetimes, client->id, strlen(client->id), client);
+		}
+	}
+
+	return MOSQ_ERR_SUCCESS;
+}
+
+
+static int callback_disconnect(int event, void *event_data, void *userdata)
+{
+	struct mosquitto_evt_disconnect *ed = event_data;
+	int i;
+	const char *id;
+	struct lifetime_s *client;
+	time_t lifetime;
+
+	UNUSED(event);
+	UNUSED(userdata);
+
+	id = mosquitto_client_id(ed->client);
+	if(id){
+		HASH_FIND(hh, local_lifetimes, id, strlen(id), client);
+		if(client){
+			HASH_DELETE(hh, local_lifetimes, client);
+
+			lifetime = time(NULL) - client->connect;
+			free(client->id);
+			free(client);
+
+			for(i=0; i<LIFETIME_COUNT; i++){
+				if(lifetime <= lifetime_values[i]){
+					lifetime_counts[i]++;
+					break;
+				}
+			}
+		}
+	}
+
+	return MOSQ_ERR_SUCCESS;
+}
+
+
+int mosquitto_plugin_init(mosquitto_plugin_id_t *identifier, void **user_data, struct mosquitto_opt *opts, int opt_count)
+{
+	UNUSED(user_data);
+	UNUSED(opts);
+	UNUSED(opt_count);
+
+	memset(lifetime_counts, 0, sizeof(lifetime_counts));
+	memset(last_lifetime_counts, 0, sizeof(last_lifetime_counts));
+
+	mosq_pid = identifier;
+	mosquitto_callback_register(mosq_pid, MOSQ_EVT_CONNECT, callback_connect, NULL, NULL);
+	mosquitto_callback_register(mosq_pid, MOSQ_EVT_DISCONNECT, callback_disconnect, NULL, NULL);
+	mosquitto_callback_register(mosq_pid, MOSQ_EVT_TICK, callback_tick, NULL, NULL);
+
+	return MOSQ_ERR_SUCCESS;
+}
diff --git a/plugins/examples/client-lifetime-stats/test.conf b/plugins/examples/client-lifetime-stats/test.conf
new file mode 100644
index 00000000..d7c7e892
--- /dev/null
+++ b/plugins/examples/client-lifetime-stats/test.conf
@@ -0,0 +1 @@
+plugin ./mosquitto_client_lifetime_stats.so
diff --git a/plugins/examples/client-lifetime-stats/test.sh b/plugins/examples/client-lifetime-stats/test.sh
new file mode 100755
index 00000000..8589ba43
--- /dev/null
+++ b/plugins/examples/client-lifetime-stats/test.sh
@@ -0,0 +1,3 @@
+#!/bin/sh
+
+../../../src/mosquitto -c test.conf -v
diff --git a/plugins/examples/delayed-auth/CMakeLists.txt b/plugins/examples/delayed-auth/CMakeLists.txt
index 76e515e9..b16c24bf 100644
--- a/plugins/examples/delayed-auth/CMakeLists.txt
+++ b/plugins/examples/delayed-auth/CMakeLists.txt
@@ -13,7 +13,7 @@ target_include_directories(${PLUGIN_NAME} PRIVATE
 
 if(WITH_BUNDLED_DEPS)
 	target_include_directories(${PLUGIN_NAME} PRIVATE
-		"${${PLUGIN_NAME}}/deps"
+		"${mosquitto_SOURCE_DIR}/deps"
 	)
 endif()
 
diff --git a/plugins/examples/payload-size-stats/CMakeLists.txt b/plugins/examples/payload-size-stats/CMakeLists.txt
new file mode 100644
index 00000000..112964b1
--- /dev/null
+++ b/plugins/examples/payload-size-stats/CMakeLists.txt
@@ -0,0 +1,26 @@
+set (PLUGIN_NAME mosquitto_payload_size_stats)
+
+add_library(${PLUGIN_NAME} MODULE
+	${PLUGIN_NAME}.c
+)
+
+target_include_directories(${PLUGIN_NAME} PRIVATE
+	"${OPENSSL_INCLUDE_DIR}"
+	"${STDBOOL_H_PATH}"
+	"${STDINT_H_PATH}"
+	"${mosquitto_SOURCE_DIR}"
+	"${mosquitto_SOURCE_DIR}/include"
+)
+
+link_directories(${mosquitto_SOURCE_DIR})
+
+set_target_properties(${PLUGIN_NAME} PROPERTIES
+	PREFIX ""
+	POSITION_INDEPENDENT_CODE 1
+)
+if(WIN32)
+	target_link_libraries(${PLUGIN_NAME} mosquitto)
+endif()
+
+# Don't install, these are example plugins only.
+#install(TARGETS ${PLUGIN_NAME} RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}" LIBRARY DESTINATION "${CMAKE_INSTALL_LIBDIR}")
diff --git a/plugins/examples/payload-size-stats/Makefile b/plugins/examples/payload-size-stats/Makefile
new file mode 100644
index 00000000..edae7bb9
--- /dev/null
+++ b/plugins/examples/payload-size-stats/Makefile
@@ -0,0 +1,28 @@
+include ../../../config.mk
+
+.PHONY : all binary check clean reallyclean test install uninstall
+
+PLUGIN_NAME=mosquitto_payload_size_stats
+PLUGIN_CFLAGS+=-I../../../include -I../../../
+
+all : binary
+
+binary : ${PLUGIN_NAME}.so
+
+${PLUGIN_NAME}.so : ${PLUGIN_NAME}.c
+	$(CROSS_COMPILE)$(CC) $(PLUGIN_CPPFLAGS) $(PLUGIN_CFLAGS) $(PLUGIN_LDFLAGS) -fPIC -shared $< -o $@
+
+reallyclean : clean
+clean:
+	-rm -f *.o ${PLUGIN_NAME}.so *.gcda *.gcno
+
+check: test
+test:
+
+install: ${PLUGIN_NAME}.so
+	# Don't install, these are examples only.
+	#$(INSTALL) -d "${DESTDIR}$(libdir)"
+	#$(INSTALL) ${STRIP_OPTS} ${PLUGIN_NAME}.so "${DESTDIR}${libdir}/${PLUGIN_NAME}.so"
+
+uninstall :
+	-rm -f "${DESTDIR}${libdir}/${PLUGIN_NAME}.so"
diff --git a/plugins/examples/payload-size-stats/mosquitto_payload_size_stats.c b/plugins/examples/payload-size-stats/mosquitto_payload_size_stats.c
new file mode 100644
index 00000000..2c8c3efb
--- /dev/null
+++ b/plugins/examples/payload-size-stats/mosquitto_payload_size_stats.c
@@ -0,0 +1,141 @@
+/*
+Copyright (c) 2021 Roger Light <roger@atchoo.org>
+
+All rights reserved. This program and the accompanying materials
+are made available under the terms of the Eclipse Public License 2.0
+and Eclipse Distribution License v1.0 which accompany this distribution.
+
+The Eclipse Public License is available at
+   https://www.eclipse.org/legal/epl-2.0/
+and the Eclipse Distribution License is available at
+  http://www.eclipse.org/org/documents/edl-v10.php.
+
+SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
+
+Contributors:
+   Roger Light - initial implementation and documentation.
+*/
+
+/*
+ * Publish statistics on message payload size.
+ *
+ * Compile with:
+ *   gcc -I<path to mosquitto-repo/include> -fPIC -shared mosquitto_payload_size_stats.c -o mosquitto_payload_size_stats.so
+ *
+ * Use in config with:
+ *
+ *   plugin /path/to/mosquitto_payload_size_stats.so
+ *
+ * Note that this only works on Mosquitto 2.0 or later.
+ */
+#include "config.h"
+
+#include <stdio.h>
+#include <string.h>
+#include <time.h>
+
+#include "mosquitto_broker.h"
+#include "mosquitto_plugin.h"
+#include "mosquitto.h"
+#include "mqtt_protocol.h"
+
+MOSQUITTO_PLUGIN_DECLARE_VERSION(5);
+
+static mosquitto_plugin_id_t *mosq_pid = NULL;
+
+#define SIZE_COUNT 28
+static const char *size_strs[SIZE_COUNT] = {
+	"0",
+	"1", "2", "5",
+	"10", "20", "50",
+	"100", "200", "500",
+	"1k", "2k", "5k",
+	"10k", "20k", "50k",
+	"100k", "200k", "500k",
+	"1M", "2M", "5M",
+	"10M", "20M", "50M",
+	"100M", "200M", "500M"
+};
+
+static uint32_t size_values[SIZE_COUNT] = {
+	0,
+	1, 2, 5,
+	10, 20, 50,
+	100, 200, 500,
+	1000, 2000, 5000,
+	10000, 20000, 50000,
+	100000, 200000, 500000,
+	1000000, 2000000, 5000000,
+	10000000, 20000000, 50000000,
+	100000000, 200000000, 500000000
+};
+
+static long size_counts[SIZE_COUNT];
+static long last_size_counts[SIZE_COUNT];
+static time_t last_report = 0;
+
+
+static int callback_tick(int event, void *event_data, void *userdata)
+{
+	struct timespec ts;
+	char topic[40];
+	char payload[40];
+	int slen;
+	int i;
+
+	UNUSED(event);
+	UNUSED(event_data);
+	UNUSED(userdata);
+
+	clock_gettime(CLOCK_REALTIME, &ts);
+	if(last_report + 10 < ts.tv_sec){
+		last_report = ts.tv_sec;
+
+		for(i=0; i<SIZE_COUNT; i++){
+			if(size_counts[i] != last_size_counts[i]){
+				snprintf(topic, sizeof(topic), "$SYS/broker/publish/sizes/%s", size_strs[i]);
+				slen = snprintf(payload, sizeof(payload), "%ld", size_counts[i]);
+				mosquitto_broker_publish_copy(NULL, topic, slen, payload, 0, 1, NULL);
+				last_size_counts[i] = size_counts[i];
+			}
+		}
+	}
+
+	return MOSQ_ERR_SUCCESS;
+}
+
+
+static int callback_message(int event, void *event_data, void *userdata)
+{
+	struct mosquitto_evt_message *ed = event_data;
+	int i;
+
+	UNUSED(event);
+	UNUSED(userdata);
+
+	for(i=0; i<SIZE_COUNT; i++){
+		if(ed->payloadlen <= size_values[i]){
+			size_counts[i]++;
+			break;
+		}
+	}
+
+	return MOSQ_ERR_SUCCESS;
+}
+
+
+int mosquitto_plugin_init(mosquitto_plugin_id_t *identifier, void **user_data, struct mosquitto_opt *opts, int opt_count)
+{
+	UNUSED(user_data);
+	UNUSED(opts);
+	UNUSED(opt_count);
+
+	memset(size_counts, 0, sizeof(size_counts));
+	memset(last_size_counts, 0, sizeof(last_size_counts));
+
+	mosq_pid = identifier;
+	mosquitto_callback_register(mosq_pid, MOSQ_EVT_MESSAGE, callback_message, NULL, NULL);
+	mosquitto_callback_register(mosq_pid, MOSQ_EVT_TICK, callback_tick, NULL, NULL);
+
+	return MOSQ_ERR_SUCCESS;
+}
diff --git a/plugins/examples/payload-size-stats/test.conf b/plugins/examples/payload-size-stats/test.conf
new file mode 100644
index 00000000..5a6d80b2
--- /dev/null
+++ b/plugins/examples/payload-size-stats/test.conf
@@ -0,0 +1 @@
+plugin ./mosquitto_payload_size_stats.so
diff --git a/plugins/examples/payload-size-stats/test.sh b/plugins/examples/payload-size-stats/test.sh
new file mode 100755
index 00000000..8589ba43
--- /dev/null
+++ b/plugins/examples/payload-size-stats/test.sh
@@ -0,0 +1,3 @@
+#!/bin/sh
+
+../../../src/mosquitto -c test.conf -v