Load and latency monitoring class.

This will allow us to assess our load level.

src/cpp/ripple/LoadMonitor.cpp

@@ -0,0 +1,66 @@
+#include "LoadMonitor.h"
+
+void LoadMonitor::LoadMonitor::update()
+{ // call with the mutex
+	time_t now = time(NULL);
+
+	if (now == mLastUpdate) // current
+		return;
+
+	if ((now < mLastUpdate) || (now > (mLastUpdate + 8)))
+	{ // way out of date
+		mCounts = 0;
+		mLatencyEvents = 0;
+		mLatencyMS = 0;
+		mLastUpdate = now;
+		return;
+	}
+
+	do
+	{ // do exponential decay
+		++mLastUpdate;
+		mCounts -= (mCounts / 4);
+		mLatencyEvents -= (mLatencyEvents / 4);
+		mLatencyMS -= (mLatencyMS / 4);
+	} while (mLastUpdate < now);
+}
+
+void LoadMonitor::addCount(int counts)
+{
+	boost::mutex::scoped_lock sl(mLock);
+
+	update();
+	mCounts += counts;
+}
+
+void LoadMonitor::addLatency(int latency)
+{
+	boost::mutex::scoped_lock sl(mLock);
+
+	update();
+	++mLatencyEvents;
+	mLatencyMS += latency;
+}
+
+void LoadMonitor::addCountAndLatency(int counts, int latency)
+{
+	boost::mutex::scoped_lock sl(mLock);
+
+	update();
+	mCounts += counts;
+	++mLatencyEvents;
+	mLatencyMS += latency;
+}
+
+void LoadMonitor::getCountAndLatency(uint64& count, uint64& latency)
+{
+	boost::mutex::scoped_lock sl(mLock);
+
+	update();
+
+	count = mCounts / 4;
+
+	if (mLatencyEvents == 0)
+		latency = 0;
+	else latency = mLatencyMS / (mLatencyEvents * 4);
+}