From b1787cbc36d44d7feccd7e9adfadf739a56cc190 Mon Sep 17 00:00:00 2001
From: Shadowghost <Shadowghost@users.noreply.github.com>
Date: Sun, 27 Sep 2026 16:30:42 -0400
Subject: Backport pull request #18095 from jellyfin/release-12.z

Retry MusicBrainz requests when the server is busy

Original-merge: 1478011dfc67c46d52d22b89a49e4519ec42bdb8

Merged-by: crobibero <cody@robibe.ro>

Backported-by: Cody Robibero <cody@robibe.ro>
---
 .../Music/MusicBrainzQueryExtensionsTests.cs       | 136 +++++++++++++++++++++
 1 file changed, 136 insertions(+)
 create mode 100644 tests/Jellyfin.Providers.Tests/Music/MusicBrainzQueryExtensionsTests.cs

(limited to 'tests')

diff --git a/tests/Jellyfin.Providers.Tests/Music/MusicBrainzQueryExtensionsTests.cs b/tests/Jellyfin.Providers.Tests/Music/MusicBrainzQueryExtensionsTests.cs
new file mode 100644
index 0000000000..6b0d3a2ab2
--- /dev/null
+++ b/tests/Jellyfin.Providers.Tests/Music/MusicBrainzQueryExtensionsTests.cs
@@ -0,0 +1,136 @@
+using System;
+using System.Globalization;
+using System.Net;
+using System.Net.Http;
+using System.Net.Http.Headers;
+using System.Threading;
+using System.Threading.Tasks;
+using MediaBrowser.Providers.Plugins.MusicBrainz;
+using MetaBrainz.Common;
+using Microsoft.Extensions.Logging.Abstractions;
+using Xunit;
+
+namespace Jellyfin.Providers.Tests.Music;
+
+public static class MusicBrainzQueryExtensionsTests
+{
+    [Fact]
+    public static async Task RetryOnTransientErrorAsync_ServerBusy_RetriesAndSucceeds()
+    {
+        var attempts = 0;
+
+        var result = await MusicBrainzQueryExtensions.RetryOnTransientErrorAsync(
+            async _ =>
+            {
+                attempts++;
+                if (attempts == 1)
+                {
+                    throw await CreateErrorAsync(HttpStatusCode.ServiceUnavailable, TimeSpan.Zero);
+                }
+
+                return "found";
+            },
+            "test",
+            NullLogger.Instance,
+            CancellationToken.None);
+
+        Assert.Equal("found", result);
+        Assert.Equal(2, attempts);
+    }
+
+    [Fact]
+    public static async Task RetryOnTransientErrorAsync_ServerStaysBusy_GivesUp()
+    {
+        var attempts = 0;
+
+        var error = await Assert.ThrowsAsync<HttpError>(() => MusicBrainzQueryExtensions.RetryOnTransientErrorAsync<string>(
+            async _ =>
+            {
+                attempts++;
+                throw await CreateErrorAsync(HttpStatusCode.ServiceUnavailable, TimeSpan.Zero);
+            },
+            "test",
+            NullLogger.Instance,
+            CancellationToken.None));
+
+        Assert.Equal(HttpStatusCode.ServiceUnavailable, error.Status);
+        Assert.Equal(3, attempts);
+    }
+
+    [Fact]
+    public static async Task RetryOnTransientErrorAsync_NotFound_DoesNotRetry()
+    {
+        var attempts = 0;
+
+        await Assert.ThrowsAsync<HttpError>(() => MusicBrainzQueryExtensions.RetryOnTransientErrorAsync<string>(
+            async _ =>
+            {
+                attempts++;
+                throw await CreateErrorAsync(HttpStatusCode.NotFound, null);
+            },
+            "test",
+            NullLogger.Instance,
+            CancellationToken.None));
+
+        Assert.Equal(1, attempts);
+    }
+
+    [Fact]
+    public static async Task GetRetryDelay_NoHint_BacksOffExponentially()
+    {
+        var error = await CreateErrorAsync(HttpStatusCode.ServiceUnavailable, null);
+
+        Assert.Equal(TimeSpan.FromSeconds(1), MusicBrainzQueryExtensions.GetRetryDelay(error, 1));
+        Assert.Equal(TimeSpan.FromSeconds(2), MusicBrainzQueryExtensions.GetRetryDelay(error, 2));
+    }
+
+    [Fact]
+    public static async Task GetRetryDelay_RetryAfterZero_WaitsMinimum()
+    {
+        var error = await CreateErrorAsync(HttpStatusCode.ServiceUnavailable, TimeSpan.Zero);
+
+        Assert.Equal(TimeSpan.FromSeconds(1), MusicBrainzQueryExtensions.GetRetryDelay(error, 1));
+    }
+
+    [Fact]
+    public static async Task GetRetryDelay_RetryAfterLongerThanBackoff_UsesRetryAfter()
+    {
+        var error = await CreateErrorAsync(HttpStatusCode.ServiceUnavailable, TimeSpan.FromSeconds(10));
+
+        Assert.Equal(TimeSpan.FromSeconds(10), MusicBrainzQueryExtensions.GetRetryDelay(error, 1));
+    }
+
+    [Fact]
+    public static async Task GetRetryDelay_LongRetryAfter_IsCapped()
+    {
+        var error = await CreateErrorAsync(HttpStatusCode.ServiceUnavailable, TimeSpan.FromHours(1));
+
+        Assert.Equal(TimeSpan.FromSeconds(15), MusicBrainzQueryExtensions.GetRetryDelay(error, 1));
+    }
+
+    [Fact]
+    public static async Task GetRetryDelay_RateLimitWindow_WaitsForReset()
+    {
+        var error = await CreateErrorAsync(
+            HttpStatusCode.ServiceUnavailable,
+            null,
+            headers => headers.TryAddWithoutValidation("X-RateLimit-Reset", DateTimeOffset.UtcNow.AddSeconds(8).ToUnixTimeSeconds().ToString(CultureInfo.InvariantCulture)));
+
+        var delay = MusicBrainzQueryExtensions.GetRetryDelay(error, 1);
+
+        Assert.InRange(delay, TimeSpan.FromSeconds(6), TimeSpan.FromSeconds(8));
+    }
+
+    private static async Task<HttpError> CreateErrorAsync(HttpStatusCode status, TimeSpan? retryAfter, Action<HttpResponseHeaders>? configureHeaders = null)
+    {
+        using var response = new HttpResponseMessage(status);
+        if (retryAfter is not null)
+        {
+            response.Headers.RetryAfter = new RetryConditionHeaderValue(retryAfter.Value);
+        }
+
+        configureHeaders?.Invoke(response.Headers);
+
+        return await HttpError.FromResponseAsync(response);
+    }
+}
-- 
cgit v1.2.3