Add HTTP call completion logging for exceptions and non-success status codes

src/ModelContextProtocol.Core/Authentication/ClientOAuthProvider.cs

@@ -341,6 +341,7 @@ private async Task<AuthorizationServerMetadata> GetAuthServerMetadataAsync(Uri a
                 var response = await _httpClient.GetAsync(wellKnownEndpoint, cancellationToken).ConfigureAwait(false);
                 if (!response.IsSuccessStatusCode)
                 {
+                    LogAuthServerMetadataNonSuccessStatusCode(wellKnownEndpoint, (int)response.StatusCode);
                     continue;
                 }
 
@@ -443,6 +444,7 @@ private static IEnumerable<Uri> GetWellKnownAuthorizationServerMetadataUris(Uri
 
         if (!httpResponse.IsSuccessStatusCode)
         {
+            LogOAuthTokenRefreshFailed((int)httpResponse.StatusCode);
             return null;
         }
 
@@ -542,6 +544,10 @@ private async Task<string> ExchangeCodeForTokenAsync(
         using var request = CreateTokenRequest(authServerMetadata.TokenEndpoint, formFields);
 
         using var httpResponse = await _httpClient.SendAsync(request, cancellationToken).ConfigureAwait(false);
+        if (!httpResponse.IsSuccessStatusCode)
+        {
+            LogOAuthTokenExchangeFailed((int)httpResponse.StatusCode);
+        }
         await httpResponse.EnsureSuccessStatusCodeWithResponseBodyAsync(cancellationToken).ConfigureAwait(false);
 
         var tokens = await HandleSuccessfulTokenResponseAsync(httpResponse, cancellationToken).ConfigureAwait(false);
@@ -619,10 +625,15 @@ private async Task<TokenContainer> HandleSuccessfulTokenResponseAsync(HttpRespon
         using var httpResponse = await _httpClient.GetAsync(metadataUrl, cancellationToken).ConfigureAwait(false);
         if (requireSuccess)
         {
+            if (!httpResponse.IsSuccessStatusCode)
+            {
+                LogProtectedResourceMetadataNonSuccessStatusCode(metadataUrl, (int)httpResponse.StatusCode);
+            }
             await httpResponse.EnsureSuccessStatusCodeWithResponseBodyAsync(cancellationToken).ConfigureAwait(false);
         }
         else if (!httpResponse.IsSuccessStatusCode)
         {
+            LogProtectedResourceMetadataNonSuccessStatusCode(metadataUrl, (int)httpResponse.StatusCode);
             return null;
         }
 
@@ -674,6 +685,7 @@ private async Task PerformDynamicClientRegistrationAsync(
 
         if (!httpResponse.IsSuccessStatusCode)
         {
+            LogDynamicClientRegistrationFailed((int)httpResponse.StatusCode);
             var errorContent = await httpResponse.Content.ReadAsStringAsync(cancellationToken).ConfigureAwait(false);
             ThrowFailedToHandleUnauthorizedResponse($"Dynamic client registration failed with status {httpResponse.StatusCode}: {errorContent}");
         }
@@ -1003,4 +1015,19 @@ private static void ThrowFailedToHandleUnauthorizedResponse(string message) =>
 
     [LoggerMessage(Level = LogLevel.Debug, Message = "Missing resource_metadata parameter from WWW-Authenticate header. Falling back to {MetadataUri}")]
     partial void LogMissingResourceMetadataParameter(Uri metadataUri);
+
+    [LoggerMessage(Level = LogLevel.Warning, Message = "Auth server metadata request to {Endpoint} received non-success status code {StatusCode}")]
+    partial void LogAuthServerMetadataNonSuccessStatusCode(Uri endpoint, int statusCode);
+
+    [LoggerMessage(Level = LogLevel.Warning, Message = "OAuth token refresh received non-success status code {StatusCode}")]
+    partial void LogOAuthTokenRefreshFailed(int statusCode);
+
+    [LoggerMessage(Level = LogLevel.Warning, Message = "OAuth token exchange received non-success status code {StatusCode}")]
+    partial void LogOAuthTokenExchangeFailed(int statusCode);
+
+    [LoggerMessage(Level = LogLevel.Warning, Message = "Protected resource metadata request to {MetadataUrl} received non-success status code {StatusCode}")]
+    partial void LogProtectedResourceMetadataNonSuccessStatusCode(Uri metadataUrl, int statusCode);
+
+    [LoggerMessage(Level = LogLevel.Warning, Message = "Dynamic client registration received non-success status code {StatusCode}")]
+    partial void LogDynamicClientRegistrationFailed(int statusCode);
 }

src/ModelContextProtocol.Core/Client/SseClientSessionTransport.cs

@@ -160,6 +160,7 @@ private async Task ReceiveMessagesAsync(CancellationToken cancellationToken)
             if (!response.IsSuccessStatusCode)
             {
                 failureStatusCode = response.StatusCode;
+                LogHttpGetSseNonSuccessStatusCode(Name, (int)response.StatusCode);
             }
 
             await response.EnsureSuccessStatusCodeWithResponseBodyAsync(cancellationToken).ConfigureAwait(false);
@@ -257,12 +258,12 @@ private void HandleEndpointEvent(string data)
         _connectionEstablished.TrySetResult(true);
     }
 
-    [LoggerMessage(Level = LogLevel.Information, Message = "{EndpointName} accepted SSE transport POST for message ID '{MessageId}'.")]
-    private partial void LogAcceptedPost(string endpointName, string messageId);
-
-    [LoggerMessage(Level = LogLevel.Information, Message = "{EndpointName} rejected SSE transport POST for message ID '{MessageId}'.")]
+    [LoggerMessage(Level = LogLevel.Warning, Message = "{EndpointName} rejected SSE transport POST for message ID '{MessageId}'.")]
     private partial void LogRejectedPost(string endpointName, string messageId);
 
     [LoggerMessage(Level = LogLevel.Trace, Message = "{EndpointName} rejected SSE transport POST for message ID '{MessageId}'. Server response: '{responseContent}'.")]
     private partial void LogRejectedPostSensitive(string endpointName, string messageId, string responseContent);
+
+    [LoggerMessage(Level = LogLevel.Warning, Message = "{EndpointName} HTTP GET SSE received non-success status code {StatusCode}.")]
+    private partial void LogHttpGetSseNonSuccessStatusCode(string endpointName, int statusCode);
 }

src/ModelContextProtocol.Core/Client/StreamableHttpClientSessionTransport.cs

@@ -91,11 +91,22 @@ internal async Task<HttpResponseMessage> SendHttpRequestAsync(JsonRpcMessage mes
 
         CopyAdditionalHeaders(httpRequestMessage.Headers, _options.AdditionalHeaders, SessionId, _negotiatedProtocolVersion);
 
-        var response = await _httpClient.SendAsync(httpRequestMessage, message, cancellationToken).ConfigureAwait(false);
+        HttpResponseMessage response;
+        try
+        {
+            response = await _httpClient.SendAsync(httpRequestMessage, message, cancellationToken).ConfigureAwait(false);
+        }
+        catch (Exception ex) when (ex is not OperationCanceledException)
+        {
+            LogHttpPostRequestFailed(Name, ex);
+            throw;
+        }
 
         // We'll let the caller decide whether to throw or fall back given an unsuccessful response.
         if (!response.IsSuccessStatusCode)
         {
+            LogHttpPostNonSuccessStatusCode(Name, (int)response.StatusCode);
+
             // Per the MCP spec, a 404 response to a request containing an Mcp-Session-Id
             // indicates the session has ended. Signal completion so McpClient.Completion resolves.
             if (response.StatusCode == HttpStatusCode.NotFound && SessionId is not null)
@@ -273,8 +284,9 @@ await SendGetSseRequestWithRetriesAsync(
             {
                 response = await _httpClient.SendAsync(request, message: null, cancellationToken).ConfigureAwait(false);
             }
-            catch (HttpRequestException)
+            catch (HttpRequestException ex)
             {
+                LogHttpGetSseRequestFailed(Name, ex);
                 attempt++;
                 continue;
             }
@@ -284,12 +296,15 @@ await SendGetSseRequestWithRetriesAsync(
                 if (response.StatusCode >= HttpStatusCode.InternalServerError)
                 {
                     // Server error; retry.
+                    LogHttpGetSseNonSuccessStatusCode(Name, (int)response.StatusCode);
                     attempt++;
                     continue;
                 }
 
                 if (!response.IsSuccessStatusCode)
                 {
+                    LogHttpGetSseNonSuccessStatusCode(Name, (int)response.StatusCode);
+
                     // Per the MCP spec, a 404 response to a request containing an Mcp-Session-Id
                     // indicates the session has ended. Signal completion so McpClient.Completion resolves.
                     if (response.StatusCode == HttpStatusCode.NotFound && SessionId is not null)
@@ -406,8 +421,25 @@ private async Task SendDeleteRequest()
         using var deleteRequest = new HttpRequestMessage(HttpMethod.Delete, _options.Endpoint);
         CopyAdditionalHeaders(deleteRequest.Headers, _options.AdditionalHeaders, SessionId, _negotiatedProtocolVersion);
 
-        // Do not validate we get a successful status code, because server support for the DELETE request is optional
-        (await _httpClient.SendAsync(deleteRequest, message: null, CancellationToken.None).ConfigureAwait(false)).Dispose();
+        HttpResponseMessage response;
+        try
+        {
+            response = await _httpClient.SendAsync(deleteRequest, message: null, CancellationToken.None).ConfigureAwait(false);
+        }
+        catch (Exception ex) when (ex is not OperationCanceledException)
+        {
+            LogHttpDeleteRequestFailed(Name, ex);
+            return;
+        }
+
+        using (response)
+        {
+            // Server support for the DELETE request is optional, so a 405 Method Not Allowed is expected.
+            if (!response.IsSuccessStatusCode)
+            {
+                LogHttpDeleteNonSuccessStatusCode(Name, (int)response.StatusCode);
+            }
+        }
     }
 
     private void LogJsonException(JsonException ex, string data)
@@ -505,4 +537,22 @@ private void SetSessionExpired()
 
         SetDisconnected(_disconnectError);
     }
+
+    [LoggerMessage(Level = LogLevel.Warning, Message = "{EndpointName} HTTP POST request failed.")]
+    private partial void LogHttpPostRequestFailed(string endpointName, Exception exception);
+
+    [LoggerMessage(Level = LogLevel.Warning, Message = "{EndpointName} HTTP POST received non-success status code {StatusCode}.")]
+    private partial void LogHttpPostNonSuccessStatusCode(string endpointName, int statusCode);
+
+    [LoggerMessage(Level = LogLevel.Warning, Message = "{EndpointName} HTTP GET SSE request failed.")]
+    private partial void LogHttpGetSseRequestFailed(string endpointName, Exception exception);
+
+    [LoggerMessage(Level = LogLevel.Warning, Message = "{EndpointName} HTTP GET SSE received non-success status code {StatusCode}.")]
+    private partial void LogHttpGetSseNonSuccessStatusCode(string endpointName, int statusCode);
+
+    [LoggerMessage(Level = LogLevel.Warning, Message = "{EndpointName} HTTP DELETE request failed.")]
+    private partial void LogHttpDeleteRequestFailed(string endpointName, Exception exception);
+
+    [LoggerMessage(Level = LogLevel.Information, Message = "{EndpointName} HTTP DELETE received non-success status code {StatusCode}.")]
+    private partial void LogHttpDeleteNonSuccessStatusCode(string endpointName, int statusCode);
 }