2 files changed, 89 insertions, 9 deletions

diff --git a/src/zenserver/stats/statsreporter.cpp b/src/zenserver/stats/statsreporter.cpp
index ff055cf18..4898f3ad5 100644
--- a/src/zenserver/stats/statsreporter.cpp
+++ b/src/zenserver/stats/statsreporter.cpp
@@ -3,12 +3,85 @@
 #include "statsreporter.h"
 
 #include <zencore/logging.h>
+#include <zencore/profiling/counterstrace.h>
 #include <zencore/trace.h>
 #include <zennet/statsdclient.h>
 
+ZEN_THIRD_PARTY_INCLUDES_START
+#include <EASTL/functional.h>
+#include <EASTL/hash_map.h>
+ZEN_THIRD_PARTY_INCLUDES_END
+
+#include <memory>
+#include <string>
+
 namespace zen {
 
-StatsReporter::StatsReporter()
+// Decorator that forwards every metric call to an inner StatsMetrics (statsd
+// in production) and additionally emits a counter trace point so the metric
+// shows up in the .utrace stream / `zen trace serve` viewer.
+//
+// Counter ids are allocated lazily on first sighting of a metric name. The
+// name string is owned by the lookup map so the TraceCounter keeps a stable
+// pointer to it for late-init re-emission.
+class TracingStatsMetrics : public StatsMetrics
+{
+public:
+	void Rebind(StatsMetrics* Inner) { m_Inner = Inner; }
+
+	void Increment(std::string_view Metric) override
+	{
+		if (m_Inner)
+			m_Inner->Increment(Metric);
+		Counter(Metric).Increment();
+	}
+
+	void Decrement(std::string_view Metric) override
+	{
+		if (m_Inner)
+			m_Inner->Decrement(Metric);
+		Counter(Metric).Decrement();
+	}
+
+	void Count(std::string_view Metric, int64_t CountDelta) override
+	{
+		if (m_Inner)
+			m_Inner->Count(Metric, CountDelta);
+		Counter(Metric).Add(CountDelta);
+	}
+
+	void Gauge(std::string_view Metric, uint64_t CurrentValue) override
+	{
+		if (m_Inner)
+			m_Inner->Gauge(Metric, CurrentValue);
+		Counter(Metric).SetAlways(int64_t(CurrentValue));
+	}
+
+	void Meter(std::string_view Metric, uint64_t IncrementValue) override
+	{
+		if (m_Inner)
+			m_Inner->Meter(Metric, IncrementValue);
+		Counter(Metric).Add(int64_t(IncrementValue));
+	}
+
+private:
+	TraceCounterInt& Counter(std::string_view Metric)
+	{
+		if (auto It = m_Counters.find_as(Metric, std::hash<std::string_view>(), eastl::equal_to_2<std::string, std::string_view>());
+			It != m_Counters.end())
+		{
+			return *It->second;
+		}
+		auto [Inserted, _] = m_Counters.try_emplace(std::string(Metric), nullptr);
+		Inserted->second   = std::make_unique<TraceCounterInt>(Inserted->first.c_str(), TraceCounterDisplayHint::None);
+		return *Inserted->second;
+	}
+
+	StatsMetrics*																									   m_Inner = nullptr;
+	eastl::hash_map<std::string, std::unique_ptr<TraceCounterInt>, std::hash<std::string>, std::equal_to<std::string>> m_Counters;
+};
+
+StatsReporter::StatsReporter() : m_TracingMetrics(std::make_unique<TracingStatsMetrics>())
 {
 }
 
@@ -52,13 +125,18 @@ void
 StatsReporter::ReportStats()
 {
 	RwLock::ExclusiveLockScope _(m_Lock);
-	if (m_Statsd)
+
+	// Always run providers through the tracing decorator so counter trace
+	// points fire even when statsd is disabled. The decorator no-ops the
+	// inner forward when m_Statsd is null.
+	m_TracingMetrics->Rebind(m_Statsd.get());
+	for (StatsProvider* Provider : m_Providers)
 	{
-		for (StatsProvider* Provider : m_Providers)
-		{
-			Provider->ReportMetrics(*m_Statsd);
-		}
+		Provider->ReportMetrics(*m_TracingMetrics);
+	}
 
+	if (m_Statsd)
+	{
 		m_Statsd->Flush();
 	}
 }
diff --git a/src/zenserver/stats/statsreporter.h b/src/zenserver/stats/statsreporter.h
index b4174073c..82219bc14 100644
--- a/src/zenserver/stats/statsreporter.h
+++ b/src/zenserver/stats/statsreporter.h
@@ -10,6 +10,7 @@
 namespace zen {
 
 class StatsDaemonClient;
+class TracingStatsMetrics;
 
 class StatsReporter
 {
@@ -26,9 +27,10 @@ public:
 	void AddProvider(StatsProvider* Provider);
 
 private:
-	RwLock							   m_Lock;
-	std::unique_ptr<StatsDaemonClient> m_Statsd;
-	std::vector<StatsProvider*>		   m_Providers;
+	RwLock								 m_Lock;
+	std::unique_ptr<StatsDaemonClient>	 m_Statsd;
+	std::unique_ptr<TracingStatsMetrics> m_TracingMetrics;	// owns counter id table; rebinds to m_Statsd
+	std::vector<StatsProvider*>			 m_Providers;
 };
 
 }  // namespace zen