diff --git a/doc/sphinx/arm/logging.rst b/doc/sphinx/arm/logging.rst
index e310da1ec4..9640627618 100644
--- a/doc/sphinx/arm/logging.rst
+++ b/doc/sphinx/arm/logging.rst
@@ -636,13 +636,13 @@ below:
 
 ::
 
-    "%D{%Y-%m-%d %H:%M:%S.%q} %-5p [%c/%i] %m\n";
+    "%D{%Y-%m-%d %H:%M:%S.%q} %-5p [%c/%i/%t] %m\n";
 
 and a typical log produced by this pattern would look somethng like this:
 
 ::
 
-    2019-08-05 14:27:45.871 DEBUG [kea-dhcp4.dhcpsrv/8475] DHCPSRV_TIMERMGR_START_TIMER starting timer: reclaim-expired-leases
+    2019-08-05 14:27:45.871 DEBUG [kea-dhcp4.dhcpsrv/8475/12345] DHCPSRV_TIMERMGR_START_TIMER starting timer: reclaim-expired-leases
 
 That breaks down as like so:
 
@@ -665,6 +665,11 @@ That breaks down as like so:
 - %i
     The process ID. From the example log: ``8475``
 
+- %t
+    The thread ID. From the example log: ``12345``.
+    Note the format of the thread ID is OS dependent: e.g. on some systems
+    it is an address so is displayed in hexadecimal.
+
 - %m
     The log message itself. Keg log messages all begin with a message
     identifier followed by arbitrary log text. Every message in Kea has
@@ -699,7 +704,7 @@ The default for pattern for syslog output is as follows:
 
 ::
 
-    "%-5p [%c] %m\n";
+    "%-5p [%c/%t] %m\n";
 
 You can see that it omits the date and time as well the process ID as this
 information is typically output by syslog.  Note that Kea uses the pattern
diff --git a/src/lib/log/output_option.cc b/src/lib/log/output_option.cc
index 459eb6b7b6..4099ec123f 100644
--- a/src/lib/log/output_option.cc
+++ b/src/lib/log/output_option.cc
@@ -18,13 +18,13 @@ namespace isc {
 namespace log {
 
 /// Default layout pattern for console logs
-const std::string OutputOption::DEFAULT_CONSOLE_PATTERN = "%D{%Y-%m-%d %H:%M:%S.%q} %-5p [%c/%i] %m\n";
+const std::string OutputOption::DEFAULT_CONSOLE_PATTERN = "%D{%Y-%m-%d %H:%M:%S.%q} %-5p [%c/%i/%t] %m\n";
 
 /// Default layout pattern for file logs
-const std::string OutputOption::DEFAULT_FILE_PATTERN = "%D{%Y-%m-%d %H:%M:%S.%q} %-5p [%c/%i] %m\n";
+const std::string OutputOption::DEFAULT_FILE_PATTERN = "%D{%Y-%m-%d %H:%M:%S.%q} %-5p [%c/%i/%t] %m\n";
 
 /// Default layout pattern for syslog logs
-const std::string OutputOption::DEFAULT_SYSLOG_PATTERN = "%-5p [%c] %m\n";
+const std::string OutputOption::DEFAULT_SYSLOG_PATTERN = "%-5p [%c/%t] %m\n";
 
 OutputOption::Destination
 getDestination(const std::string& dest_str) {
diff --git a/src/lib/log/tests/buffer_logger_test.sh.in b/src/lib/log/tests/buffer_logger_test.sh.in
index 8687225bb3..976a26c04a 100644
--- a/src/lib/log/tests/buffer_logger_test.sh.in
+++ b/src/lib/log/tests/buffer_logger_test.sh.in
@@ -1,5 +1,5 @@
 #!/bin/sh
-# Copyright (C) 2012-2016 Internet Systems Consortium, Inc. ("ISC")
+# Copyright (C) 2012-2020 Internet Systems Consortium, Inc. ("ISC")
 #
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
@@ -32,7 +32,7 @@ INFO  [buffertest.log] LOG_BAD_SEVERITY unrecognized log severity: info
 INFO  [buffertest.log] LOG_BAD_SEVERITY unrecognized log severity: info
 .
 ./buffer_logger_test 2>&1 | \
-    sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\]/[\1]/' | \
+    sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\/\(0x\)\{0,1\}\([0-9A-Fa-f]\{1,\}\)\]/[\1]/' | \
     cut -d' ' -f3- | diff $tempfile -
 passfail $?
 
diff --git a/src/lib/log/tests/destination_test.sh.in b/src/lib/log/tests/destination_test.sh.in
index e79138a316..393027bc6b 100644
--- a/src/lib/log/tests/destination_test.sh.in
+++ b/src/lib/log/tests/destination_test.sh.in
@@ -1,5 +1,5 @@
 #!/bin/sh
-# Copyright (C) 2011-2016 Internet Systems Consortium, Inc. ("ISC")
+# Copyright (C) 2011-2020 Internet Systems Consortium, Inc. ("ISC")
 #
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
@@ -36,9 +36,11 @@ ERROR [example.beta] LOG_BAD_DESTINATION unrecognized log destination: beta_erro
 rm -f $destfile1 $destfile2
 ./logger_example -s error -f $destfile1_tmp -f $destfile2_tmp
 
-# strip the pids
-sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\]/[\1]/' < $destfile1_tmp > $destfile1
-sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\]/[\1]/' < $destfile2_tmp > $destfile2
+# strip the pids and thread ids
+sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\/\(0x\)\{0,1\}\([0-9A-Fa-f]\{1,\}\)\]/[\1]/' < $destfile1_tmp > $destfile1
+sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\/\(0x\)\{0,1\}\([0-9A-Fa-f]\{1,\}\)\]/[\1]/' < $destfile2_tmp > $destfile2
+# strip the thread ids
+
 
 echo -n  "   - destination 1:"
 cut -d' ' -f3- $destfile1 | diff $tempfile -
@@ -55,9 +57,9 @@ echo     "2. Two loggers, different destinations and severities"
 rm -f $destfile1 $destfile2
 ./logger_example -l example -s info -f $destfile1_tmp -l alpha -s warn -f $destfile2_tmp
 
-# strip the pids
-sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\]/[\1]/' < $destfile1_tmp > $destfile1
-sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\]/[\1]/' < $destfile2_tmp > $destfile2
+# strip the pids and thread ids
+sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\/\(0x\)\{0,1\}\([0-9A-Fa-f]\{1,\}\)\]/[\1]/' < $destfile1_tmp > $destfile1
+sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\/\(0x\)\{0,1\}\([0-9A-Fa-f]\{1,\}\)\]/[\1]/' < $destfile2_tmp > $destfile2
 
 # All output for example and example.beta should have gone to destfile1.
 # Output for example.alpha should have done to destfile2.
diff --git a/src/lib/log/tests/init_logger_test.sh.in b/src/lib/log/tests/init_logger_test.sh.in
index 50530c873c..8ceb02d287 100644
--- a/src/lib/log/tests/init_logger_test.sh.in
+++ b/src/lib/log/tests/init_logger_test.sh.in
@@ -1,5 +1,5 @@
 #!/bin/sh
-# Copyright (C) 2011-2016 Internet Systems Consortium, Inc. ("ISC")
+# Copyright (C) 2011-2020 Internet Systems Consortium, Inc. ("ISC")
 #
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
@@ -38,7 +38,7 @@ ERROR [kea.log] LOG_DUPLICATE_MESSAGE_ID duplicate message ID (error) in compile
 FATAL [kea.log] LOG_NO_MESSAGE_ID line fatal: message definition line found without a message ID
 .
 KEA_LOGGER_DESTINATION=stdout KEA_LOGGER_SEVERITY=DEBUG KEA_LOGGER_DBGLEVEL=99 ./init_logger_test | \
-    sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\]/[\1]/' | \
+    sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\/\(0x\)\{0,1\}\([0-9A-Fa-f]\{1,\}\)\]/[\1]/' | \
     cut -d' ' -f3- | diff $tempfile -
 passfail $?
 
@@ -52,7 +52,7 @@ ERROR [kea.log] LOG_DUPLICATE_MESSAGE_ID duplicate message ID (error) in compile
 FATAL [kea.log] LOG_NO_MESSAGE_ID line fatal: message definition line found without a message ID
 .
 KEA_LOGGER_DESTINATION=stdout KEA_LOGGER_SEVERITY=DEBUG KEA_LOGGER_DBGLEVEL=50 ./init_logger_test | \
-    sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\]/[\1]/' | \
+    sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\/\(0x\)\{0,1\}\([0-9A-Fa-f]\{1,\}\)\]/[\1]/' | \
     cut -d' ' -f3- | diff $tempfile -
 passfail $?
 
@@ -63,7 +63,7 @@ ERROR [kea.log] LOG_DUPLICATE_MESSAGE_ID duplicate message ID (error) in compile
 FATAL [kea.log] LOG_NO_MESSAGE_ID line fatal: message definition line found without a message ID
 .
 KEA_LOGGER_DESTINATION=stdout KEA_LOGGER_SEVERITY=WARN ./init_logger_test | \
-    sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\]/[\1]/' | \
+    sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\/\(0x\)\{0,1\}\([0-9A-Fa-f]\{1,\}\)\]/[\1]/' | \
     cut -d' ' -f3- | diff $tempfile -
 passfail $?
 
@@ -75,21 +75,21 @@ FATAL [kea.log] LOG_NO_MESSAGE_ID line fatal: message definition line found with
 .
 rm -f $destfile_tmp $destfile
 KEA_LOGGER_SEVERITY=FATAL KEA_LOGGER_DESTINATION=stdout ./init_logger_test 1> $destfile_tmp
-sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\]/[\1]/' < $destfile_tmp > $destfile
+sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\/\(0x\)\{0,1\}\([0-9A-Fa-f]\{1,\}\)\]/[\1]/' < $destfile_tmp > $destfile
 cut -d' ' -f3- $destfile | diff $tempfile -
 passfail $?
 
 echo -n  "   - stderr: "
 rm -f $destfile_tmp $destfile
 KEA_LOGGER_SEVERITY=FATAL KEA_LOGGER_DESTINATION=stderr ./init_logger_test 2> $destfile_tmp
-sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\]/[\1]/' < $destfile_tmp > $destfile
+sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\/\(0x\)\{0,1\}\([0-9A-Fa-f]\{1,\}\)\]/[\1]/' < $destfile_tmp > $destfile
 cut -d' ' -f3- $destfile | diff $tempfile -
 passfail $?
 
 echo -n  "   - file: "
 rm -f $destfile_tmp $destfile
 KEA_LOGGER_SEVERITY=FATAL KEA_LOGGER_DESTINATION=$destfile_tmp ./init_logger_test
-sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\]/[\1]/' < $destfile_tmp > $destfile
+sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\/\(0x\)\{0,1\}\([0-9A-Fa-f]\{1,\}\)\]/[\1]/' < $destfile_tmp > $destfile
 cut -d' ' -f3- $destfile | diff $tempfile -
 passfail $?
 
diff --git a/src/lib/log/tests/local_file_test.sh.in b/src/lib/log/tests/local_file_test.sh.in
index fa4c449d85..dd3035cf3d 100644
--- a/src/lib/log/tests/local_file_test.sh.in
+++ b/src/lib/log/tests/local_file_test.sh.in
@@ -1,5 +1,5 @@
 #!/bin/sh
-# Copyright (C) 2011-2016 Internet Systems Consortium, Inc. ("ISC")
+# Copyright (C) 2011-2020 Internet Systems Consortium, Inc. ("ISC")
 #
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
@@ -44,7 +44,7 @@ ERROR [example.beta] LOG_BAD_DESTINATION unrecognized log destination: beta_erro
 WARN  [example.beta] LOG_BAD_STREAM bad log console output stream: beta_warn
 .
 ./logger_example -c stdout -s warn $localmes | \
-    sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\]/[\1]/' | \
+    sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\/\(0x\)\{0,1\}\([0-9A-Fa-f]\{1,\}\)\]/[\1]/' | \
     cut -d' ' -f3- | diff $tempfile -
 passfail $?
 
@@ -61,7 +61,7 @@ WARN  [example.beta] LOG_BAD_STREAM bad log console output stream: beta_warn
 .
 rm -f $localmes
 ./logger_example -c stdout -s warn $localmes | \
-    sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\]/[\1]/' | \
+    sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\/\(0x\)\{0,1\}\([0-9A-Fa-f]\{1,\}\)\]/[\1]/' | \
     cut -d' ' -f3- | diff $tempfile -
 passfail $?
 
diff --git a/src/lib/log/tests/logger_lock_test.sh.in b/src/lib/log/tests/logger_lock_test.sh.in
index 1da24fe96b..f25fd07413 100644
--- a/src/lib/log/tests/logger_lock_test.sh.in
+++ b/src/lib/log/tests/logger_lock_test.sh.in
@@ -1,5 +1,5 @@
 #!/bin/sh
-# Copyright (C) 2012-2016 Internet Systems Consortium, Inc. ("ISC")
+# Copyright (C) 2012-2020 Internet Systems Consortium, Inc. ("ISC")
 #
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
@@ -30,7 +30,7 @@ LOGGER_LOCK_TEST: UNLOCK
 .
 rm -f $destfile
 KEA_LOGGER_SEVERITY=INFO KEA_LOGGER_DESTINATION=stdout ./logger_lock_test | \
-    sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\]/[\1]/' > $destfile
+    sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\/\(0x\)\{0,1\}\([0-9A-Fa-f]\{1,\}\)\]/[\1]/' > $destfile
 cut -d' ' -f3- $destfile | diff $tempfile -
 passfail $?
 
diff --git a/src/lib/log/tests/logger_manager_unittest.cc b/src/lib/log/tests/logger_manager_unittest.cc
index 5f7ed9a0c9..516a2a1796 100644
--- a/src/lib/log/tests/logger_manager_unittest.cc
+++ b/src/lib/log/tests/logger_manager_unittest.cc
@@ -1,4 +1,4 @@
-// Copyright (C) 2011-2017 Internet Systems Consortium, Inc. ("ISC")
+// Copyright (C) 2011-2020 Internet Systems Consortium, Inc. ("ISC")
 //
 // This Source Code Form is subject to the terms of the Mozilla Public
 // License, v. 2.0. If a copy of the MPL was not distributed with this
@@ -50,8 +50,6 @@ public:
     }
 };
 
-
-
 // Convenience class to create the specification for the logger "filelogger",
 // which, as the name suggests, logs to a file.  It remembers the file name and
 // deletes the file when instance of the class is destroyed.
@@ -134,7 +132,6 @@ private:
     string                  logname_;   // Name of this logger
 };
 
-
 // Convenience function to read an output log file and check that each line
 // contains the expected message ID
 //
@@ -392,8 +389,8 @@ TEST_F(LoggerManagerTest, checkLayoutPattern) {
                       "[[:digit:]]{2}:[[:digit:]]{2}:[[:digit:]]{2}\\.[[:digit:]]+[[:space:]]"
                       // %-5p
                       "[[:alpha:]]{1,5}[[:space:]]"
-                      // [%c/%i]
-                      "\\[[[:alnum:]\\-\\.]+/[[:digit:]]+\\][[:space:]]"
+                      // [%c/%i/%t]
+                      "\\[[[:alnum:]\\-\\.]+/[[:digit:]]+/(0x)?[[:xdigit:]]+\\][[:space:]]"
                       );
 
     const int re = regexec(*regex, line.c_str(), 0, NULL, 0);
diff --git a/src/lib/log/tests/severity_test.sh.in b/src/lib/log/tests/severity_test.sh.in
index 762391df58..2efe21db39 100644
--- a/src/lib/log/tests/severity_test.sh.in
+++ b/src/lib/log/tests/severity_test.sh.in
@@ -1,5 +1,5 @@
 #!/bin/sh
-# Copyright (C) 2011-2016 Internet Systems Consortium, Inc. ("ISC")
+# Copyright (C) 2011-2020 Internet Systems Consortium, Inc. ("ISC")
 #
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
@@ -36,7 +36,7 @@ WARN  [example.beta] LOG_BAD_STREAM bad log console output stream: beta_warn
 INFO  [example.beta] LOG_READ_ERROR error reading from message file beta: info
 .
 ./logger_example -c stdout | \
-    sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\]/[\1]/' | \
+    sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\/\(0x\)\{0,1\}\([0-9A-Fa-f]\{1,\}\)\]/[\1]/' | \
     cut -d' ' -f3- | diff $tempfile -
 passfail $?
 
@@ -48,7 +48,7 @@ FATAL [example.beta] LOG_BAD_SEVERITY unrecognized log severity: beta_fatal
 ERROR [example.beta] LOG_BAD_DESTINATION unrecognized log destination: beta_error
 .
 ./logger_example -c stdout -s error | \
-    sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\]/[\1]/' | \
+    sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\/\(0x\)\{0,1\}\([0-9A-Fa-f]\{1,\}\)\]/[\1]/' | \
     cut -d' ' -f3- | diff $tempfile -
 passfail $?
 
@@ -69,7 +69,7 @@ INFO  [example.beta] LOG_READ_ERROR error reading from message file beta: info
 DEBUG [example.beta] LOG_BAD_SEVERITY unrecognized log severity: beta/25
 .
 ./logger_example -c stdout -s debug -d 25 | \
-    sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\]/[\1]/' | \
+    sed -e 's/\[\([a-z0-9\.]\{1,\}\)\/\([0-9]\{1,\}\)\/\(0x\)\{0,1\}\([0-9A-Fa-f]\{1,\}\)\]/[\1]/' | \
     cut -d' ' -f3- | diff $tempfile -
 passfail $?