1 files changed, 223 insertions, 0 deletions

diff --git a/OpenSim/Framework/MetricsCollector.cs b/OpenSim/Framework/MetricsCollector.cs
new file mode 100644
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+++ b/OpenSim/Framework/MetricsCollector.cs
@@ -0,0 +1,223 @@
+using System;
+using System.Diagnostics;
+
+namespace OpenSim.Framework
+{
+    /// <summary>
+    /// A MetricsCollector for 'long' values.
+    /// </summary>
+    public class MetricsCollectorLong : MetricsCollector<long>
+    {
+        public MetricsCollectorLong(int windowSize, int numBuckets)
+            : base(windowSize, numBuckets)
+        {
+        }
+
+        protected override long GetZero() { return 0; }
+
+        protected override long Add(long a, long b) { return a + b; }
+    }
+
+
+    /// <summary>
+    /// A MetricsCollector for time spans.
+    /// </summary>
+    public class MetricsCollectorTime : MetricsCollectorLong
+    {
+        public MetricsCollectorTime(int windowSize, int numBuckets)
+            : base(windowSize, numBuckets)
+        {
+        }
+
+        public void AddSample(Stopwatch timer)
+        {
+            long ticks = timer.ElapsedTicks;
+            if (ticks > 0)
+                AddSample(ticks);
+        }
+
+        public TimeSpan GetSumTime()
+        {
+            return TimeSpan.FromMilliseconds((GetSum() * 1000) / Stopwatch.Frequency);
+        }
+    }
+
+    
+    struct MetricsBucket<T>
+    {
+        public T value;
+        public int count;
+    }
+
+    
+    /// <summary>
+    /// Collects metrics in a sliding window.
+    /// </summary>
+    /// <remarks>
+    /// MetricsCollector provides the current Sum of the metrics that it collects. It can easily be extended
+    /// to provide the Average, too. It uses a sliding window to keep these values current.
+    /// 
+    /// This class is not thread-safe.
+    /// 
+    /// Subclass MetricsCollector to have it use a concrete value type. Override the abstract methods.
+    /// </remarks>
+    public abstract class MetricsCollector<T>
+    {
+        private int bucketSize;     // e.g. 3,000 ms
+
+        private MetricsBucket<T>[] buckets;
+
+        private int NumBuckets { get { return buckets.Length; } }
+
+
+        // The number of the current bucket, if we had an infinite number of buckets and didn't have to wrap around
+        long curBucketGlobal;
+
+        // The total of all the buckets
+        T totalSum;
+        int totalCount;
+
+
+        /// <summary>
+        /// Returns the default (zero) value.
+        /// </summary>
+        /// <returns></returns>
+        protected abstract T GetZero();
+
+        /// <summary>
+        /// Adds two values.
+        /// </summary>
+        protected abstract T Add(T a, T b);
+
+
+        /// <summary>
+        /// Creates a MetricsCollector.
+        /// </summary>
+        /// <param name="windowSize">The period of time over which to collect the metrics, in ms. E.g.: 30,000.</param>
+        /// <param name="numBuckets">The number of buckets to divide the samples into. E.g.: 10. Using more buckets
+        /// smooths the jarring that occurs whenever we drop an old bucket, but uses more memory.</param>
+        public MetricsCollector(int windowSize, int numBuckets)
+        {
+            bucketSize = windowSize / numBuckets;
+            buckets = new MetricsBucket<T>[numBuckets];
+            Reset();
+        }
+
+        public void Reset()
+        {
+            ZeroBuckets(0, NumBuckets);
+            curBucketGlobal = GetNow() / bucketSize;
+            totalSum = GetZero();
+            totalCount = 0;
+        }
+
+        public void AddSample(T sample)
+        {
+            MoveWindow();
+
+            int curBucket = (int)(curBucketGlobal % NumBuckets);
+            buckets[curBucket].value = Add(buckets[curBucket].value, sample);
+            buckets[curBucket].count++;
+
+            totalSum = Add(totalSum, sample);
+            totalCount++;
+        }
+
+        /// <summary>
+        /// Returns the total values in the collection window.
+        /// </summary>
+        public T GetSum()
+        {
+            // It might have been a while since we last added a sample, so we may need to adjust the window
+            MoveWindow();
+
+            return totalSum;
+        }
+
+        /// <summary>
+        /// Returns the current time in ms.
+        /// </summary>
+        private long GetNow()
+        {
+            return DateTime.Now.Ticks / TimeSpan.TicksPerMillisecond;
+        }
+
+        /// <summary>
+        /// Clears the values in buckets [offset, offset+num)
+        /// </summary>
+        private void ZeroBuckets(int offset, int num)
+        {
+            for (int i = 0; i < num; i++)
+            {
+                buckets[offset + i].value = GetZero();
+                buckets[offset + i].count = 0;
+            }
+        }
+
+        /// <summary>
+        /// Adjusts the buckets so that the "current bucket" corresponds to the current time.
+        /// This may require dropping old buckets.
+        /// </summary>
+        /// <remarks>
+        /// This method allows for the possibility that we don't get new samples for each bucket, so the
+        /// new bucket may be some distance away from the last used bucket.
+        /// </remarks>
+        private void MoveWindow()
+        {
+            long newBucketGlobal = GetNow() / bucketSize;
+            long bucketsDistance = newBucketGlobal - curBucketGlobal;
+
+            if (bucketsDistance == 0)
+            {
+                // We're still on the same bucket as before
+                return;
+            }
+
+            if (bucketsDistance >= NumBuckets)
+            {
+                // Discard everything
+                Reset();
+                return;
+            }
+
+            int curBucket = (int)(curBucketGlobal % NumBuckets);
+            int newBucket = (int)(newBucketGlobal % NumBuckets);
+
+
+            // Clear all the buckets in this range: (cur, new]
+            int numToClear = (int)bucketsDistance;
+
+            if (curBucket < NumBuckets - 1)
+            {
+                // Clear buckets at the end of the window
+                int num = Math.Min((int)bucketsDistance, NumBuckets - (curBucket + 1));
+                ZeroBuckets(curBucket + 1, num);
+                numToClear -= num;
+            }
+
+            if (numToClear > 0)
+            {
+                // Clear buckets at the beginning of the window
+                ZeroBuckets(0, numToClear);
+            }
+
+            // Move the "current bucket" pointer
+            curBucketGlobal = newBucketGlobal;
+
+            RecalcTotal();
+        }
+
+        private void RecalcTotal()
+        {
+            totalSum = GetZero();
+            totalCount = 0;
+
+            for (int i = 0; i < NumBuckets; i++)
+            {
+                totalSum = Add(totalSum, buckets[i].value);
+                totalCount += buckets[i].count;
+            }
+        }
+
+    }
+}