stats: Completed Meter implementation

1 files changed, 48 insertions, 12 deletions

diff --git a/zencore/include/zencore/stats.h b/zencore/include/zencore/stats.h
index 7290fd914..0554f620d 100644
--- a/zencore/include/zencore/stats.h
+++ b/zencore/include/zencore/stats.h
@@ -12,30 +12,44 @@ template<typename T>
 class Gauge
 {
 public:
-	Gauge() : m_value{0} {}
+	Gauge() : m_Value{0} {}
+
+	T	 Value() const { return m_Value; }
+	void SetValue(T Value) { m_Value = Value; }
 
 private:
-	T m_value;
+	std::atomic<T> m_Value;
 };
 
+/** Stats counter
+ *
+ * A counter is modified by adding or subtracting a value from a current value.
+ * This would typically be used to track number of requests in flight, number
+ * of active jobs etc
+ *
+ */
 class Counter
 {
 public:
 	inline void		SetValue(uint64_t Value) { m_count = Value; }
 	inline uint64_t Value() const { return m_count; }
 
-	inline void Increment(int64_t AddValue) { m_count += AddValue; }
-	inline void Decrement(int64_t SubValue) { m_count -= SubValue; }
-	inline void Clear() { m_count = 0; }
+	inline void Increment(int64_t AddValue) { m_count.fetch_add(AddValue); }
+	inline void Decrement(int64_t SubValue) { m_count.fetch_sub(SubValue); }
+	inline void Clear() { m_count.store(0, std::memory_order_release); }
 
 private:
-	std::atomic_uint64_t m_count{0};
+	std::atomic<uint64_t> m_count{0};
 };
 
-/// <summary>
-/// Exponential Weighted Moving Average
-/// </summary>
-class EWMA
+/** Exponential Weighted Moving Average
+
+	This is very raw, to use as little state as possible. If we
+	want to use this more broadly in user code we should perhaps
+	add a more user-friendly wrapper
+ */
+
+class RawEWMA
 {
 public:
 	/// <summary>
@@ -49,16 +63,38 @@ public:
 	double Rate() const;
 
 private:
-	double m_rate = 0;
+	std::atomic<double> m_Rate = 0;
 };
 
 /// <summary>
-/// Tracks rate of events over time (i.e requests/sec)
+/// Tracks rate of events over time (i.e requests/sec), using
+/// exponential moving averages
 /// </summary>
 class Meter
 {
 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
+
 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
+	bool				  m_IsFirstTick = true;
+	RawEWMA				  m_RateM1;
+	RawEWMA				  m_RateM5;
+	RawEWMA				  m_RateM15;
+
+	void TickIfNecessary();
+	void Tick();
 };
 
 extern void stats_forcelink();