Initial commit, basic proxying working

2020-12-22 13:15:26 +01:00
parent c3f6becea4
commit a6fbd869be
109 changed files with 3539 additions and 359 deletions
--- a/Myriad/Rest/Ratelimit/Bucket.cs
+++ b/Myriad/Rest/Ratelimit/Bucket.cs
@@ -0,0 +1,152 @@
+using System;
+using System.Threading;
+
+using Serilog;
+
+namespace Myriad.Rest.Ratelimit
+{
+    public class Bucket
+    {
+        private static readonly TimeSpan Epsilon = TimeSpan.FromMilliseconds(10);
+        private static readonly TimeSpan FallbackDelay = TimeSpan.FromMilliseconds(200);
+
+        private static readonly TimeSpan StaleTimeout = TimeSpan.FromSeconds(5);
+
+        private readonly ILogger _logger;
+        private readonly SemaphoreSlim _semaphore = new(1, 1);
+
+        private DateTimeOffset _nextReset;
+        private bool _resetTimeValid;
+
+        public Bucket(ILogger logger, string key, ulong major, int limit)
+        {
+            _logger = logger.ForContext<Bucket>();
+
+            Key = key;
+            Major = major;
+
+            Limit = limit;
+            Remaining = limit;
+            _resetTimeValid = false;
+        }
+
+        public string Key { get; }
+        public ulong Major { get; }
+
+        public int Remaining { get; private set; }
+
+        public int Limit { get; private set; }
+
+        public DateTimeOffset LastUsed { get; private set; } = DateTimeOffset.UtcNow;
+
+        public bool TryAcquire()
+        {
+            LastUsed = DateTimeOffset.Now;
+
+            try
+            {
+                _semaphore.Wait();
+
+                if (Remaining > 0)
+                {
+                    _logger.Debug(
+                        "{BucketKey}/{BucketMajor}: Bucket has [{BucketRemaining}/{BucketLimit} left], allowing through",
+                        Key, Major, Remaining, Limit);
+                    Remaining--;
+                    return true;
+                }
+
+                _logger.Debug("{BucketKey}/{BucketMajor}: Bucket has [{BucketRemaining}/{BucketLimit}] left, denying",
+                    Key, Major, Remaining, Limit);
+                return false;
+            }
+            finally
+            {
+                _semaphore.Release();
+            }
+        }
+
+        public void HandleResponse(RatelimitHeaders headers)
+        {
+            try
+            {
+                _semaphore.Wait();
+
+                if (headers.ResetAfter != null)
+                {
+                    var headerNextReset = DateTimeOffset.UtcNow + headers.ResetAfter.Value; // todo: server time
+                    if (headerNextReset > _nextReset)
+                    {
+                        _logger.Debug("{BucketKey}/{BucketMajor}: Received reset time {NextReset} from server",
+                            Key, Major, _nextReset);
+
+                        _nextReset = headerNextReset;
+                        _resetTimeValid = true;
+                    }
+                }
+
+                if (headers.Limit != null)
+                    Limit = headers.Limit.Value;
+            }
+            finally
+            {
+                _semaphore.Release();
+            }
+        }
+
+        public void Tick(DateTimeOffset now)
+        {
+            try
+            {
+                _semaphore.Wait();
+
+                // If we're past the reset time *and* we haven't reset already, do that
+                var timeSinceReset = _nextReset - now;
+                var shouldReset = _resetTimeValid && timeSinceReset > TimeSpan.Zero;
+                if (shouldReset)
+                {
+                    _logger.Debug("{BucketKey}/{BucketMajor}: Bucket timed out, refreshing with {BucketLimit} requests",
+                        Key, Major, Limit);
+                    Remaining = Limit;
+                    _resetTimeValid = false;
+                    return;
+                }
+
+                // We've run out of requests without having any new reset time,
+                // *and* it's been longer than a set amount - add one request back to the pool and hope that one returns
+                var isBucketStale = !_resetTimeValid && Remaining <= 0 && timeSinceReset > StaleTimeout;
+                if (isBucketStale)
+                {
+                    _logger.Warning(
+                        "{BucketKey}/{BucketMajor}: Bucket is stale ({StaleTimeout} passed with no rate limit info), allowing one request through",
+                        Key, Major, StaleTimeout);
+
+                    Remaining = 1;
+
+                    // Reset the (still-invalid) reset time to now, so we don't keep hitting this conditional over and over...
+                    _nextReset = now;
+                }
+            }
+            finally
+            {
+                _semaphore.Release();
+            }
+        }
+
+        public TimeSpan GetResetDelay(DateTimeOffset now)
+        {
+            // If we don't have a valid reset time, return the fallback delay always
+            // (so it'll keep spinning until we hopefully have one...)
+            if (!_resetTimeValid)
+                return FallbackDelay;
+
+            var delay = _nextReset - now;
+
+            // If we have a really small (or negative) value, return a fallback delay too
+            if (delay < Epsilon)
+                return FallbackDelay;
+
+            return delay;
+        }
+    }
+}