Feature/ratelimit refactor (#197)

2026-08-23 06:13:09 +00:00 · 2024-04-16 14:55:27 +02:00
parent 2dbd5be924
commit 1b1961db00
57 changed files with 2294 additions and 688 deletions
@@ -0,0 +1,103 @@
+using System;
+using System.Collections.Generic;
+using CryptoExchange.Net.RateLimiting.Interfaces;
+
+namespace CryptoExchange.Net.RateLimiting.Trackers
+{
+    internal class FixedAfterStartWindowTracker : IWindowTracker
+    {
+        /// <inheritdoc />
+        public TimeSpan TimePeriod { get; }
+        /// <inheritdoc />
+        public int Limit { get; }
+        /// <inheritdoc />
+        public int Current => _currentWeight;
+
+        private readonly Queue<LimitEntry> _entries;
+        private int _currentWeight = 0;
+        private DateTime? _nextReset;
+
+        /// <summary>
+        /// Additional wait time to apply to account for time offset between server and client
+        /// </summary>
+        private static TimeSpan _fixedWindowBuffer = TimeSpan.FromMilliseconds(1000);
+
+        public FixedAfterStartWindowTracker(int limit, TimeSpan period)
+        {
+            Limit = limit;
+            TimePeriod = period;
+            _entries = new Queue<LimitEntry>();
+        }
+
+        public TimeSpan GetWaitTime(int weight)
+        {
+            // Remove requests no longer in time period from the history
+            var checkTime = DateTime.UtcNow;
+            if (_nextReset != null && checkTime > _nextReset)
+                RemoveBefore(_nextReset.Value);
+
+            if (Current == 0)
+                _nextReset = null;
+
+            if (Current + weight > Limit)
+            {
+                // The weight would cause the rate limit to be passed
+                if (Current == 0)
+                {
+                    throw new Exception("Request limit reached without any prior request. " +
+                        $"This request can never execute with the current rate limiter. Request weight: {weight}, Ratelimit: {Limit}");
+                }
+
+                // Determine the time to wait before this weight can be applied without going over the rate limit
+                return DetermineWaitTime();
+            }
+
+            // Weight can fit without going over limit
+            return TimeSpan.Zero;
+        }
+
+        /// <inheritdoc />
+        public void ApplyWeight(int weight)
+        {
+            if (_currentWeight == 0)
+                _nextReset = DateTime.UtcNow + TimePeriod;
+            _currentWeight += weight;
+            _entries.Enqueue(new LimitEntry(DateTime.UtcNow, weight));
+        }
+
+        /// <summary>
+        /// Remove items before a certain time
+        /// </summary>
+        /// <param name="time"></param>
+        protected void RemoveBefore(DateTime time)
+        {
+            while (true)
+            {
+                if (_entries.Count == 0)
+                    break;
+
+                var firstItem = _entries.Peek();
+                if (firstItem.Timestamp < time)
+                {
+                    _entries.Dequeue();
+                    _currentWeight -= firstItem.Weight;
+                }
+                else
+                {
+                    // Either no entries left, or the entry time is still within the window
+                    break;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Determine the time to wait before a new item would fit
+        /// </summary>
+        /// <returns></returns>
+        private TimeSpan DetermineWaitTime()
+        {
+            var checkTime = DateTime.UtcNow;
+            return (_nextReset!.Value - checkTime) + _fixedWindowBuffer;
+        }
+    }
+}