Fixed: Don't apply indexer backoff on DNS and connection issues.

Fixes #751

src/NzbDrone.Core/Indexers/HttpIndexerBase.cs

@@ -202,7 +202,16 @@ namespace NzbDrone.Core.Indexers
             }
             catch (WebException webException)
             {
-                _indexerStatusService.RecordFailure(Definition.Id);
+                if (webException.Status == WebExceptionStatus.NameResolutionFailure ||
+                    webException.Status == WebExceptionStatus.ConnectFailure)
+                {
+                    _indexerStatusService.RecordConnectionFailure(Definition.Id);
+                }
+                else
+                {
+                    _indexerStatusService.RecordFailure(Definition.Id);
+                }
+
                 if (webException.Message.Contains("502") || webException.Message.Contains("503") ||
                     webException.Message.Contains("timed out"))
                 {

src/NzbDrone.Core/Indexers/IndexerStatusService.cs

@@ -15,6 +15,7 @@ namespace NzbDrone.Core.Indexers
         ReleaseInfo GetLastRssSyncReleaseInfo(int indexerId);
         void RecordSuccess(int indexerId);
         void RecordFailure(int indexerId, TimeSpan minimumBackOff = default(TimeSpan));
+        void RecordConnectionFailure(int indexerId);
 
         void UpdateRssSyncStatus(int indexerId, ReleaseInfo releaseInfo);
     }
@@ -85,7 +86,7 @@ namespace NzbDrone.Core.Indexers
             }
         }
 
-        public void RecordFailure(int indexerId, TimeSpan minimumBackOff = default(TimeSpan))
+        protected void RecordFailure(int indexerId, TimeSpan minimumBackOff, bool escalate)
         {
             lock (_syncRoot)
             {
@@ -99,7 +100,10 @@ namespace NzbDrone.Core.Indexers
                 }
 
                 status.MostRecentFailure = now;
-                status.EscalationLevel = Math.Min(MaximumEscalationLevel, status.EscalationLevel + 1);
+                if (escalate)
+                {
+                    status.EscalationLevel = Math.Min(MaximumEscalationLevel, status.EscalationLevel + 1);
+                }
 
                 if (minimumBackOff != TimeSpan.Zero)
                 {
@@ -115,6 +119,17 @@ namespace NzbDrone.Core.Indexers
             }
         }
 
+        public void RecordFailure(int indexerId, TimeSpan minimumBackOff = default(TimeSpan))
+        {
+            RecordFailure(indexerId, minimumBackOff, true);
+        }
+
+        public void RecordConnectionFailure(int indexerId)
+        {
+            RecordFailure(indexerId, default(TimeSpan), false);
+        }
+
+
         public void UpdateRssSyncStatus(int indexerId, ReleaseInfo releaseInfo)
         {
             lock (_syncRoot)