diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4e80cc01..8112b724 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -65,6 +65,7 @@ set (NANO_WARN_TO_ERR OFF CACHE BOOL "")
 set (NANO_TIMED_LOCKS 0 CACHE STRING "")
 set (NANO_TIMED_LOCKS_IGNORE_BLOCKED OFF CACHE BOOL "")
 set (NANO_FUZZER_TEST OFF CACHE BOOL "")
+set (NANO_ASIO_HANDLER_TRACKING 0 CACHE STRING "")
 
 option (NANO_STACKTRACE_BACKTRACE "Use BOOST_STACKTRACE_USE_BACKTRACE in stacktraces, for POSIX" OFF)
 if (NANO_STACKTRACE_BACKTRACE)
@@ -81,6 +82,10 @@ if (${NANO_TIMED_LOCKS} GREATER 0)
 	endif ()
 endif ()
 
+if (${NANO_ASIO_HANDLER_TRACKING} GREATER 0)
+	add_definitions (-DNANO_ASIO_HANDLER_TRACKING=${NANO_ASIO_HANDLER_TRACKING} -DBOOST_ASIO_ENABLE_HANDLER_TRACKING)
+endif ()
+
 add_definitions (-DNANO_ROCKSDB=$<STREQUAL:${NANO_ROCKSDB},ON>)
 
 option(NANO_ASAN_INT "Enable ASan+UBSan+Integer overflow" OFF)
diff --git a/nano/lib/threading.cpp b/nano/lib/threading.cpp
index 0b0319bd..9d54240c 100644
--- a/nano/lib/threading.cpp
+++ b/nano/lib/threading.cpp
@@ -1,6 +1,9 @@
 #include <nano/lib/threading.hpp>
 
+#include <boost/format.hpp>
+
 #include <iostream>
+#include <thread>
 
 namespace
 {
@@ -124,7 +127,26 @@ io_guard (boost::asio::make_work_guard (io_ctx_a))
 			nano::thread_role::set (nano::thread_role::name::io);
 			try
 			{
+#if NANO_ASIO_HANDLER_TRACKING == 0
 				io_ctx_a.run ();
+#else
+				nano::timer<> timer;
+				timer.start ();
+				while (true)
+				{
+					timer.restart ();
+					// Run at most 1 completion handler and record the time it took to complete (non-blocking)
+					auto count = io_ctx_a.poll_one ();
+					if (count == 1 && timer.since_start ().count () >= NANO_ASIO_HANDLER_TRACKING)
+					{
+						auto timestamp = std::chrono::duration_cast<std::chrono::microseconds> (std::chrono::system_clock::now ().time_since_epoch ()).count ();
+						std::cout << (boost::format ("[%1%] io_thread held for %2%ms") % timestamp % timer.since_start ().count ()).str () << std::endl;
+					}
+					// Sleep for a bit to give more time slices to other threads
+					std::this_thread::sleep_for (std::chrono::milliseconds (5));
+					std::this_thread::yield ();
+				}
+#endif
 			}
 			catch (std::exception const & ex)
 			{
diff --git a/nano/node/testing.cpp b/nano/node/testing.cpp
index d185779f..5aa08e47 100644
--- a/nano/node/testing.cpp
+++ b/nano/node/testing.cpp
@@ -226,9 +226,24 @@ void nano::system::deadline_set (std::chrono::duration<double, std::nano> const
 
 std::error_code nano::system::poll (std::chrono::nanoseconds const & wait_time)
 {
-	std::error_code ec;
+#if NANO_ASIO_HANDLER_TRACKING == 0
 	io_ctx.run_one_for (wait_time);
+#else
+	nano::timer<> timer;
+	timer.start ();
+	auto count = io_ctx.poll_one ();
+	if (count == 0)
+	{
+		std::this_thread::sleep_for (wait_time);
+	}
+	else if (count == 1 && timer.since_start ().count () >= NANO_ASIO_HANDLER_TRACKING)
+	{
+		auto timestamp = std::chrono::duration_cast<std::chrono::microseconds> (std::chrono::system_clock::now ().time_since_epoch ()).count ();
+		std::cout << (boost::format ("[%1%] io_thread held for %2%ms") % timestamp % timer.since_start ().count ()).str () << std::endl;
+	}
+#endif
 
+	std::error_code ec;
 	if (std::chrono::steady_clock::now () > deadline)
 	{
 		ec = nano::error_system::deadline_expired;