Feature: Implement a user controlled rate limit.

src/NzbDrone.Core/Indexers/HttpIndexerBase.cs

@@ -43,7 +43,7 @@ public abstract class HttpIndexerBase<TSettings> : IndexerBase<TSettings>
                     { Exception: HttpException { Response.HasHttpServerError: true } } => PredicateResult.True(),
                     _ => PredicateResult.False()
                 },
-                Delay = RateLimit,
+                Delay = GetResolvedRateLimit(),
                 MaxRetryAttempts = 2,
                 BackoffType = DelayBackoffType.Exponential,
                 UseJitter = true,
@@ -81,6 +81,31 @@ public abstract class HttpIndexerBase<TSettings> : IndexerBase<TSettings>
         public virtual int PageSize => 0;
         public virtual TimeSpan RateLimit => TimeSpan.FromSeconds(2);
 
+        private TimeSpan GetResolvedRateLimit(TimeSpan? requestDelay = null)
+        {
+            var systemDelay = requestDelay ?? TimeSpan.Zero;
+
+            if (systemDelay < RateLimit)
+            {
+                systemDelay = RateLimit;
+            }
+
+            if (Settings?.BaseSettings?.RequestDelay is null or < 2 or > 60)
+            {
+                return systemDelay;
+            }
+
+            var userDelay = TimeSpan.FromSeconds(Settings.BaseSettings.RequestDelay.Value);
+
+            if (userDelay > systemDelay)
+            {
+                _logger.Trace("Using user defined request delay of {0} seconds for indexer {1}", userDelay.TotalSeconds, Definition.Name);
+                return userDelay;
+            }
+
+            return systemDelay;
+        }
+
         public abstract IIndexerRequestGenerator GetRequestGenerator();
         public abstract IParseIndexerResponse GetParser();
 
@@ -236,11 +261,7 @@ public override async Task<IndexerDownloadResponse> Download(Uri link)
                 return new IndexerDownloadResponse(Encoding.UTF8.GetBytes(request.Url.FullUri));
             }
 
-            if (request.RateLimit < RateLimit)
-            {
-                request.RateLimit = RateLimit;
-            }
-
+            request.RateLimit = GetResolvedRateLimit(request.RateLimit);
             request.AllowAutoRedirect = false;
 
             byte[] fileData;
@@ -636,10 +657,7 @@ protected virtual async Task<IndexerResponse> FetchIndexerResponse(IndexerReques
         {
             _logger.Debug("Downloading Feed " + request.HttpRequest.ToString(false));
 
-            if (request.HttpRequest.RateLimit < RateLimit)
-            {
-                request.HttpRequest.RateLimit = RateLimit;
-            }
+            request.HttpRequest.RateLimit = GetResolvedRateLimit(request.HttpRequest.RateLimit);
 
             if (_configService.LogIndexerResponse)
             {
@@ -716,11 +734,7 @@ protected async Task<HttpResponse> ExecuteAuth(HttpRequest request)
                 request.RequestTimeout = TimeSpan.FromSeconds(15);
             }
 
-            if (request.RateLimit < RateLimit)
-            {
-                request.RateLimit = RateLimit;
-            }
-
+            request.RateLimit = GetResolvedRateLimit(request.RateLimit);
             var response = await _httpClient.ExecuteProxiedAsync(request, Definition);
 
             _eventAggregator.PublishEvent(new IndexerAuthEvent(Definition.Id, !response.HasHttpError, response.ElapsedTime));

src/NzbDrone.Core/Indexers/IndexerBaseSettings.cs

@@ -16,6 +16,10 @@ public IndexerCommonSettingsValidator()
                 .GreaterThan(0)
                 .When(c => c.GrabLimit.HasValue)
                 .WithMessage("Should be greater than zero");
+
+            RuleFor(c => c.RequestDelay)
+                .InclusiveBetween(2, 60)
+                .When(c => c.RequestDelay.HasValue);
         }
     }
 
@@ -29,6 +33,9 @@ public class IndexerBaseSettings
 
         [FieldDefinition(3, Type = FieldType.Select, Label = "IndexerSettingsLimitsUnit", SelectOptions = typeof(IndexerLimitsUnit), HelpText = "IndexerSettingsLimitsUnitHelpText", Advanced = true)]
         public int LimitsUnit { get; set; } = (int)IndexerLimitsUnit.Day;
+
+        [FieldDefinition(4, Type = FieldType.Number, Label = "IndexerSettingsRequestDelay", HelpText = "IndexerSettingsRequestDelayHelpText", Advanced = true)]
+        public double? RequestDelay { get; set; }
     }
 
     public enum IndexerLimitsUnit

src/NzbDrone.Core/Localization/Core/en.json

@@ -428,6 +428,8 @@
   "IndexerSettingsPreferMagnetUrlHelpText": "When enabled, this indexer will prefer the use of magnet URLs for grabs with fallback to torrent links",
   "IndexerSettingsQueryLimit": "Query Limit",
   "IndexerSettingsQueryLimitHelpText": "The number of max queries as specified by the respective unit that {appName} will allow to the site",
+  "IndexerSettingsRequestDelay": "Minimum Request Delay",
+  "IndexerSettingsRequestDelayHelpText": "Minimum delay in seconds between requests for this indexer. The rate limit can only be increased by this setting. Setting a lower value than the default delay will be ignored.",
   "IndexerSettingsRssKey": "RSS Key",
   "IndexerSettingsSeedRatio": "Seed Ratio",
   "IndexerSettingsSeedRatioHelpText": "The ratio a torrent should reach before stopping, empty uses the download client's default. Ratio should be at least 1.0 and follow the indexers rules",