Only delay making request if necessary

When requesting data from MusicBrainz, only delay the request if previous request was less than rate limit ago, instead of always delaying for one second at start.

MediaBrowser.Providers/Music/MusicBrainzAlbumProvider.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.Globalization;
 using System.IO;
 using System.Linq;
@@ -28,6 +29,7 @@ namespace MediaBrowser.Providers.Music
         private readonly IApplicationHost _appHost;
         private readonly ILogger _logger;
         private readonly IJsonSerializer _json;
+        private Stopwatch _stopWatchMusicBrainz = new Stopwatch();
 
         public readonly string MusicBrainzBaseUrl;
 
@@ -45,6 +47,9 @@ namespace MediaBrowser.Providers.Music
 
             MusicBrainzBaseUrl = configuration["MusicBrainz:BaseUrl"];
 
+            // Use a stopwatch to ensure we don't exceed the MusicBrainz rate limit
+            _stopWatchMusicBrainz.Start();
+
             Current = this;
         }
 
@@ -54,8 +59,6 @@ namespace MediaBrowser.Providers.Music
             var releaseGroupId = searchInfo.GetReleaseGroupId();
 
             string url;
-            var isNameSearch = false;
-            bool forceMusicBrainzProper = false;
 
             if (!string.IsNullOrEmpty(releaseId))
             {
@@ -64,7 +67,6 @@ namespace MediaBrowser.Providers.Music
             else if (!string.IsNullOrEmpty(releaseGroupId))
             {
                 url = string.Format("/ws/2/release?release-group={0}", releaseGroupId);
-                forceMusicBrainzProper = true;
             }
             else
             {
@@ -78,8 +80,6 @@ namespace MediaBrowser.Providers.Music
                 }
                 else
                 {
-                    isNameSearch = true;
-
                     // I'm sure there is a better way but for now it resolves search for 12" Mixes
                     var queryName = searchInfo.Name.Replace("\"", string.Empty);
 
@@ -91,7 +91,7 @@ namespace MediaBrowser.Providers.Music
 
             if (!string.IsNullOrWhiteSpace(url))
             {
-                using (var response = await GetMusicBrainzResponse(url, isNameSearch, forceMusicBrainzProper, cancellationToken).ConfigureAwait(false))
+                using (var response = await GetMusicBrainzResponse(url, cancellationToken).ConfigureAwait(false))
                 {
                     using (var stream = response.Content)
                     {
@@ -247,7 +247,7 @@ namespace MediaBrowser.Providers.Music
                 WebUtility.UrlEncode(albumName),
                 artistId);
 
-            using (var response = await GetMusicBrainzResponse(url, true, cancellationToken).ConfigureAwait(false))
+            using (var response = await GetMusicBrainzResponse(url, cancellationToken).ConfigureAwait(false))
             using (var stream = response.Content)
             using (var oReader = new StreamReader(stream, Encoding.UTF8))
             {
@@ -272,7 +272,7 @@ namespace MediaBrowser.Providers.Music
                 WebUtility.UrlEncode(albumName),
                 WebUtility.UrlEncode(artistName));
 
-            using (var response = await GetMusicBrainzResponse(url, true, cancellationToken).ConfigureAwait(false))
+            using (var response = await GetMusicBrainzResponse(url, cancellationToken).ConfigureAwait(false))
             using (var stream = response.Content)
             using (var oReader = new StreamReader(stream, Encoding.UTF8))
             {
@@ -589,7 +589,7 @@ namespace MediaBrowser.Providers.Music
         {
             var url = string.Format("/ws/2/release?release-group={0}", releaseGroupId);
 
-            using (var response = await GetMusicBrainzResponse(url, true, true, cancellationToken).ConfigureAwait(false))
+            using (var response = await GetMusicBrainzResponse(url, cancellationToken).ConfigureAwait(false))
             using (var stream = response.Content)
             using (var oReader = new StreamReader(stream, Encoding.UTF8))
             {
@@ -625,7 +625,7 @@ namespace MediaBrowser.Providers.Music
         {
             var url = string.Format("/ws/2/release-group/?query=reid:{0}", releaseEntryId);
 
-            using (var response = await GetMusicBrainzResponse(url, false, cancellationToken).ConfigureAwait(false))
+            using (var response = await GetMusicBrainzResponse(url, cancellationToken).ConfigureAwait(false))
             using (var stream = response.Content)
             using (var oReader = new StreamReader(stream, Encoding.UTF8))
             {
@@ -710,34 +710,32 @@ namespace MediaBrowser.Providers.Music
             return null;
         }
 
-        internal Task<HttpResponseInfo> GetMusicBrainzResponse(string url, bool isSearch, CancellationToken cancellationToken)
-        {
-            return GetMusicBrainzResponse(url, isSearch, false, cancellationToken);
-        }
-
         /// <summary>
-        /// Gets the music brainz response.
+        /// Makes request to MusicBrainz server and awaits a response.
         /// </summary>
-        internal async Task<HttpResponseInfo> GetMusicBrainzResponse(string url, bool isSearch, bool forceMusicBrainzProper, CancellationToken cancellationToken)
+        internal async Task<HttpResponseInfo> GetMusicBrainzResponse(string url, CancellationToken cancellationToken)
         {
-            var urlInfo = new MbzUrl(MusicBrainzBaseUrl, 1000);
-            var throttleMs = urlInfo.throttleMs;
+            // The Jellyfin user-agent is unrestricted but source IP must not exceed
+            // one request per second, therefore we rate limit to avoid throttling
+            // https://musicbrainz.org/doc/XML_Web_Service/Rate_Limiting
+            const long QueryIntervalMs = 1000u;
 
-            if (throttleMs > 0)
+            // Only delay if necessary
+            if (_stopWatchMusicBrainz.ElapsedMilliseconds < QueryIntervalMs)
             {
-                // MusicBrainz is extremely adamant about limiting to one request per second
-                _logger.LogDebug("Throttling MusicBrainz by {0}ms", throttleMs.ToString(CultureInfo.InvariantCulture));
-                await Task.Delay(throttleMs, cancellationToken).ConfigureAwait(false);
+                var delayMs = QueryIntervalMs - _stopWatchMusicBrainz.ElapsedMilliseconds;
+                await Task.Delay((int)delayMs, cancellationToken).ConfigureAwait(false);
             }
 
-            url = urlInfo.url.TrimEnd('/') + url;
+            _logger.LogDebug("MusicBrainz time since previous request: {0}ms", _stopWatchMusicBrainz.ElapsedMilliseconds);
+            _stopWatchMusicBrainz.Restart();
 
             var options = new HttpRequestOptions
             {
-                Url = url,
+                Url = MusicBrainzBaseUrl.TrimEnd('/') + url,
                 CancellationToken = cancellationToken,
                 UserAgent = _appHost.ApplicationUserAgent,
-                BufferContent = throttleMs > 0
+                BufferContent = false
             };
 
             return await _httpClient.SendAsync(options, "GET").ConfigureAwait(false);
@@ -749,17 +747,5 @@ namespace MediaBrowser.Providers.Music
         {
             throw new NotImplementedException();
         }
-
-        internal class MbzUrl
-        {
-            internal MbzUrl(string url, int throttleMs)
-            {
-                this.url = url;
-                this.throttleMs = throttleMs;
-            }
-
-            public string url { get; set; }
-            public int throttleMs { get; set; }
-        }
     }
 }

MediaBrowser.Providers/Music/MusicBrainzArtistProvider.cs

@@ -31,7 +31,7 @@ namespace MediaBrowser.Providers.Music
             {
                 var url = string.Format("/ws/2/artist/?query=arid:{0}", musicBrainzId);
 
-                using (var response = await MusicBrainzAlbumProvider.Current.GetMusicBrainzResponse(url, false, cancellationToken).ConfigureAwait(false))
+                using (var response = await MusicBrainzAlbumProvider.Current.GetMusicBrainzResponse(url, cancellationToken).ConfigureAwait(false))
                 {
                     using (var stream = response.Content)
                     {
@@ -46,7 +46,7 @@ namespace MediaBrowser.Providers.Music
 
                 var url = string.Format("/ws/2/artist/?query=\"{0}\"&dismax=true", UrlEncode(nameToSearch));
 
-                using (var response = await MusicBrainzAlbumProvider.Current.GetMusicBrainzResponse(url, true, cancellationToken).ConfigureAwait(false))
+                using (var response = await MusicBrainzAlbumProvider.Current.GetMusicBrainzResponse(url, cancellationToken).ConfigureAwait(false))
                 {
                     using (var stream = response.Content)
                     {
@@ -64,7 +64,7 @@ namespace MediaBrowser.Providers.Music
                     // Try again using the search with accent characters url
                     url = string.Format("/ws/2/artist/?query=artistaccent:\"{0}\"", UrlEncode(nameToSearch));
 
-                    using (var response = await MusicBrainzAlbumProvider.Current.GetMusicBrainzResponse(url, true, cancellationToken).ConfigureAwait(false))
+                    using (var response = await MusicBrainzAlbumProvider.Current.GetMusicBrainzResponse(url, cancellationToken).ConfigureAwait(false))
                     {
                         using (var stream = response.Content)
                         {