stats: Added EmitSnapshot functions to emit metrics into CbObjects

2 files changed, 52 insertions, 14 deletions

diff --git a/zencore/include/zencore/stats.h b/zencore/include/zencore/stats.h
index 7665d0cf5..f61184ced 100644
--- a/zencore/include/zencore/stats.h
+++ b/zencore/include/zencore/stats.h
@@ -7,6 +7,10 @@
 #include <atomic>
 #include <random>
 
+namespace zen {
+class CbObjectWriter;
+}
+
 namespace zen::metrics {
 
 template<typename T>
@@ -77,18 +81,19 @@ public:
 	Meter();
 	~Meter();
 
-	double Rate1();					  // One-minute rate
-	double Rate5();					  // Five-minute rate
-	double Rate15();				  // Fifteen-minute rate
-	double MeanRate();				  // Mean rate since instantiation of this meter
-	void   Mark(uint64_t Count = 1);  // Register one or more events
+	inline uint64_t Count() const { return m_TotalCount; }
+	double			Rate1();				   // One-minute rate
+	double			Rate5();				   // Five-minute rate
+	double			Rate15();				   // Fifteen-minute rate
+	double			MeanRate() const;		   // Mean rate since instantiation of this meter
+	void			Mark(uint64_t Count = 1);  // Register one or more events
 
 private:
 	std::atomic<uint64_t> m_TotalCount{0};	  // Accumulator counting number of marks since beginning
 	std::atomic<uint64_t> m_PendingCount{0};  // Pending EWMA update accumulator
 	std::atomic<uint64_t> m_StartTick{0};	  // Time this was instantiated (for mean)
 	std::atomic<uint64_t> m_LastTick{0};	  // Timestamp of last EWMA tick
-	std::atomic<int64_t>  m_Remain{0};		  // Tracks the "modulo" of tick time
+	std::atomic<int64_t>  m_Remainder{0};	  // Tracks the "modulo" of tick time
 	bool				  m_IsFirstTick = true;
 	RawEWMA				  m_RateM1;
 	RawEWMA				  m_RateM5;
@@ -175,6 +180,9 @@ private:
 	std::atomic<int64_t> m_Count{0};
 };
 
+void EmitSnapshot(std::string_view Tag, const Histogram& Stat, CbObjectWriter& Cbo);
+void EmitSnapshot(std::string_view Tag, Meter& Stat, CbObjectWriter& Cbo);
+
 }  // namespace zen::metrics
 
 namespace zen {
diff --git a/zencore/stats.cpp b/zencore/stats.cpp
index 2a9b0a06f..53086f3ec 100644
--- a/zencore/stats.cpp
+++ b/zencore/stats.cpp
@@ -1,6 +1,8 @@
 // Copyright Epic Games, Inc. All Rights Reserved.
 
 #include "zencore/stats.h"
+
+#include <zencore/compactbinarybuilder.h>
 #include "zencore/intmath.h"
 #include "zencore/thread.h"
 #include "zencore/timer.h"
@@ -79,18 +81,18 @@ Meter::TickIfNecessary()
 
 		if (m_LastTick.compare_exchange_strong(OldTick, NewTick))
 		{
-			m_Remain.fetch_add(Age);
+			m_Remainder.fetch_add(Age);
 
 			do
 			{
-				int64_t Remain = m_Remain.load(std::memory_order_relaxed);
+				int64_t Remain = m_Remainder.load(std::memory_order_relaxed);
 
 				if (Remain < 0)
 				{
 					return;
 				}
 
-				if (m_Remain.compare_exchange_strong(Remain, Remain - CountPerTick))
+				if (m_Remainder.compare_exchange_strong(Remain, Remain - CountPerTick))
 				{
 					Tick();
 				}
@@ -140,7 +142,7 @@ Meter::Rate15()
 }
 
 double
-Meter::MeanRate()
+Meter::MeanRate() const
 {
 	const uint64_t Count = m_TotalCount.load(std::memory_order_relaxed);
 
@@ -222,7 +224,7 @@ UniformSample::Update(int64_t Value)
 SampleSnapshot
 UniformSample::Snapshot() const
 {
-	uint64_t ValuesSize = Size();
+	uint64_t			ValuesSize = Size();
 	std::vector<double> Values(ValuesSize);
 
 	for (int i = 0; i < ValuesSize; ++i)
@@ -336,8 +338,8 @@ SampleSnapshot::GetQuantileValue(double Quantile)
 	}
 
 	const int32_t Index = (int32_t)Pos;
-	const double Lower = m_Values[Index - 1];
-	const double Upper = m_Values[Index];
+	const double  Lower = m_Values[Index - 1];
+	const double  Upper = m_Values[Index];
 
 	// Lerp
 	return Lower + (Pos - std::floor(Pos)) * (Upper - Lower);
@@ -351,6 +353,34 @@ SampleSnapshot::GetValues() const
 
 //////////////////////////////////////////////////////////////////////////
 
+void
+EmitSnapshot(std::string_view Tag, const Histogram& Stat, CbObjectWriter& Cbo)
+{
+	Cbo.BeginObject(Tag);
+
+	SampleSnapshot Snap = Stat.Snapshot();
+
+	Cbo << "count" << Stat.Count() << "avg" << Stat.Mean();
+	Cbo << "min" << Stat.Min() << "max" << Stat.Max();
+	Cbo << "p75" << Snap.Get75Percentile() << "p95" << Snap.Get95Percentile() << "p99" << Snap.Get99Percentile() << "p999"
+		<< Snap.Get999Percentile();
+
+	Cbo.EndObject();
+}
+
+void
+EmitSnapshot(std::string_view Tag, Meter& Stat, CbObjectWriter& Cbo)
+{
+	Cbo.BeginObject(Tag);
+
+	Cbo << "count" << Stat.Count() << "rate_mean" << Stat.MeanRate();
+	Cbo << "rate_1" << Stat.Rate1() << "rate_5" << Stat.Rate5() << "rate_15" << Stat.Rate15();
+
+	Cbo.EndObject();
+}
+
+//////////////////////////////////////////////////////////////////////////
+
 #if ZEN_WITH_TESTS
 
 TEST_CASE("Core.Stats.Histogram")
@@ -378,7 +408,7 @@ TEST_CASE("Core.Stats.Histogram")
 	Histo.Update(-2);
 	CHECK_EQ(Histo.Min(), -2);
 	CHECK_EQ(Histo.Max(), 2);
-	CHECK_EQ(Histo.Mean(), 1/3.0);
+	CHECK_EQ(Histo.Mean(), 1 / 3.0);
 
 	SampleSnapshot Snap4 = Histo.Snapshot();
 	CHECK_EQ(Snap4.Size(), 3);