Include Cloudflare Ray ID into log messages when the HTTP response is…

… not successful

src/ConfigCat.Client.Tests/BasicConfigCatClientIntegrationTests.cs

@@ -475,4 +475,29 @@ public async Task SpecialCharacters_Works(string settingKey, string userId, stri
         var actual = await client.GetValueAsync(settingKey, "NOT_CAT", new User(userId));
         Assert.AreEqual(expectedValue, actual);
     }
+
+    [TestMethod]
+    public async Task ShouldIncludeRayIdInLogMessagesWhenHttpResponseIsNotSuccessful()
+    {
+        var logEvents = new List<LogEvent>();
+        var logger = LoggingHelper.CreateCapturingLogger(logEvents, LogLevel.Info);
+
+        using IConfigCatClient client = ConfigCatClient.Get("configcat-sdk-1/~~~~~~~~~~~~~~~~~~~~~~/~~~~~~~~~~~~~~~~~~~~~~", options =>
+        {
+            options.PollingMode = PollingModes.ManualPoll;
+            options.Logger = logger;
+        });
+
+        await client.ForceRefreshAsync();
+
+        var errors = logEvents.Where(evt => evt.EventId == 1100).ToArray();
+        Assert.AreEqual(1, errors.Length);
+
+        var rayId = errors[0].Message.ArgValues[0] as string;
+        Assert.IsNotNull(rayId);
+        Assert.AreNotEqual("", rayId);
+        Assert.AreNotEqual(LoggerExtensions.FormatRayId(null), rayId);
+
+        StringAssert.Contains(errors[0].Message.InvariantFormattedMessage, rayId);
+    }
 }

src/ConfigCatClient/ConfigService/DefaultConfigFetcher.cs

@@ -89,7 +89,7 @@ private async ValueTask<FetchResult> FetchInternalAsync(ProjectConfig lastConfig
                     if (config is null)
                     {
                         var exception = deserializedResponse.Exception;
-                        logMessage = this.logger.FetchReceived200WithInvalidBody(exception);
+                        logMessage = this.logger.FetchReceived200WithInvalidBody(response.RayId, exception);
                         return FetchResult.Failure(lastConfig, RefreshErrorCode.InvalidHttpResponseContent, logMessage.ToLazyString(), exception);
                     }
 
@@ -104,21 +104,21 @@ private async ValueTask<FetchResult> FetchInternalAsync(ProjectConfig lastConfig
                 case HttpStatusCode.NotModified:
                     if (lastConfig.IsEmpty)
                     {
-                        logMessage = this.logger.FetchReceived304WhenLocalCacheIsEmpty((int)response.StatusCode, response.ReasonPhrase);
+                        logMessage = this.logger.FetchReceived304WhenLocalCacheIsEmpty((int)response.StatusCode, response.ReasonPhrase, response.RayId);
                         return FetchResult.Failure(lastConfig, RefreshErrorCode.InvalidHttpResponseWhenLocalCacheIsEmpty, logMessage.ToLazyString());
                     }
 
                     return FetchResult.NotModified(lastConfig.With(ProjectConfig.GenerateTimeStamp()));
 
                 case HttpStatusCode.Forbidden:
                 case HttpStatusCode.NotFound:
-                    logMessage = this.logger.FetchFailedDueToInvalidSdkKey();
+                    logMessage = this.logger.FetchFailedDueToInvalidSdkKey(response.RayId);
 
                     // We update the timestamp for extra protection against flooding.
                     return FetchResult.Failure(lastConfig.With(ProjectConfig.GenerateTimeStamp()), RefreshErrorCode.InvalidSdkKey, logMessage.ToLazyString());
 
                 default:
-                    logMessage = this.logger.FetchFailedDueToUnexpectedHttpResponse((int)response.StatusCode, response.ReasonPhrase);
+                    logMessage = this.logger.FetchFailedDueToUnexpectedHttpResponse((int)response.StatusCode, response.ReasonPhrase, response.RayId);
                     return FetchResult.Failure(lastConfig, RefreshErrorCode.UnexpectedHttpResponse, logMessage.ToLazyString());
             }
         }
@@ -193,7 +193,7 @@ private async ValueTask<DeserializedResponse> FetchRequestAsync(string? httpETag
 
                     if (maxExecutionCount <= 1)
                     {
-                        this.logger.FetchFailedDueToRedirectLoop();
+                        this.logger.FetchFailedDueToRedirectLoop(response.RayId);
                         return new DeserializedResponse(response, config);
                     }
 

src/ConfigCatClient/ConfigService/FetchResponse.cs

@@ -1,4 +1,7 @@
+using System.Linq;
 using System.Net;
+using System.Net.Http;
+using System.Net.Http.Headers;
 
 namespace ConfigCat.Client;
 
@@ -7,17 +10,27 @@ namespace ConfigCat.Client;
 /// </summary>
 public readonly struct FetchResponse
 {
-    /// <summary>
-    /// Initializes a new instance of the <see cref="FetchResponse"/> struct.
-    /// </summary>
-    public FetchResponse(HttpStatusCode statusCode, string? reasonPhrase, string? eTag, string? body)
+    internal static FetchResponse From(HttpResponseMessage httpResponse, string? httpResponseBody = null)
+    {
+        return new FetchResponse(httpResponse.StatusCode, httpResponse.ReasonPhrase, httpResponse.Headers, httpResponseBody);
+    }
+
+    private readonly object? headersOrETag; // either null or a string or HttpResponseHeaders
+
+    private FetchResponse(HttpStatusCode statusCode, string? reasonPhrase, object? headersOrETag, string? body)
     {
         StatusCode = statusCode;
         ReasonPhrase = reasonPhrase;
-        ETag = eTag;
+        this.headersOrETag = headersOrETag;
         Body = body;
     }
 
+    /// <summary>
+    /// Initializes a new instance of the <see cref="FetchResponse"/> struct.
+    /// </summary>
+    public FetchResponse(HttpStatusCode statusCode, string? reasonPhrase, string? eTag, string? body)
+        : this(statusCode, reasonPhrase, (object?)eTag, body) { }
+
     /// <summary>
     /// The HTTP status code.
     /// </summary>
@@ -31,7 +44,9 @@ public FetchResponse(HttpStatusCode statusCode, string? reasonPhrase, string? eT
     /// <summary>
     /// The value of the <c>ETag</c> HTTP response header.
     /// </summary>
-    public string? ETag { get; }
+    public string? ETag => this.headersOrETag is HttpResponseHeaders headers ? headers.ETag?.Tag : (string?)this.headersOrETag;
+
+    internal string? RayId => this.headersOrETag is HttpResponseHeaders headers && headers.TryGetValues("CF-RAY", out var values) ? values.FirstOrDefault() : null;
 
     /// <summary>
     /// The response body.

src/ConfigCatClient/ConfigService/HttpClientConfigFetcher.cs

@@ -90,11 +90,11 @@ public async Task<FetchResponse> FetchAsync(FetchRequest request, CancellationTo
                 var httpResponseBody = await httpResponse.Content.ReadAsStringAsync().ConfigureAwait(TaskShim.ContinueOnCapturedContext);
 #endif
 
-                return new FetchResponse(httpResponse.StatusCode, httpResponse.ReasonPhrase, httpResponse.Headers.ETag?.Tag, httpResponseBody);
+                return FetchResponse.From(httpResponse, httpResponseBody);
             }
             else
             {
-                var response = new FetchResponse(httpResponse.StatusCode, httpResponse.ReasonPhrase, eTag: null, body: null);
+                var response = FetchResponse.From(httpResponse);
                 if (!response.IsExpected)
                 {
                     this.httpClient = null;

src/ConfigCatClient/Logging/LogMessages.cs

@@ -38,14 +38,15 @@ public static FormattableLogMessage ForceRefreshError(this LoggerWrapper logger,
         $"Error occurred in the `{methodName}` method.",
         "METHOD_NAME");
 
-    public static FormattableLogMessage FetchFailedDueToInvalidSdkKey(this LoggerWrapper logger) => logger.Log(
+    public static FormattableLogMessage FetchFailedDueToInvalidSdkKey(this LoggerWrapper logger, string? rayId) => logger.LogInterpolated(
         LogLevel.Error, 1100,
-        "Your SDK Key seems to be wrong. You can find the valid SDK Key at https://app.configcat.com/sdkkey");
+        $"Your SDK Key seems to be wrong. You can find the valid SDK Key at https://app.configcat.com/sdkkey (Ray ID: {FormatRayId(rayId)})",
+        "RAY_ID");
 
-    public static FormattableLogMessage FetchFailedDueToUnexpectedHttpResponse(this LoggerWrapper logger, int statusCode, string? reasonPhrase) => logger.LogInterpolated(
+    public static FormattableLogMessage FetchFailedDueToUnexpectedHttpResponse(this LoggerWrapper logger, int statusCode, string? reasonPhrase, string? rayId) => logger.LogInterpolated(
         LogLevel.Error, 1101,
-        $"Unexpected HTTP response was received while trying to fetch config JSON: {statusCode} {reasonPhrase}",
-        "STATUS_CODE", "REASON_PHRASE");
+        $"Unexpected HTTP response was received while trying to fetch config JSON: {statusCode} {reasonPhrase} (Ray ID: {FormatRayId(rayId)})",
+        "STATUS_CODE", "REASON_PHRASE", "RAY_ID");
 
     public static FormattableLogMessage FetchFailedDueToRequestTimeout(this LoggerWrapper logger, TimeSpan timeout, Exception ex) => logger.LogInterpolated(
         LogLevel.Error, 1102, ex,
@@ -56,18 +57,20 @@ public static FormattableLogMessage FetchFailedDueToUnexpectedError(this LoggerW
         LogLevel.Error, 1103, ex,
         "Unexpected error occurred while trying to fetch config JSON. It is most likely due to a local network issue. Please make sure your application can reach the ConfigCat CDN servers (or your proxy server) over HTTP.");
 
-    public static FormattableLogMessage FetchFailedDueToRedirectLoop(this LoggerWrapper logger) => logger.Log(
+    public static FormattableLogMessage FetchFailedDueToRedirectLoop(this LoggerWrapper logger, string? rayId) => logger.LogInterpolated(
         LogLevel.Error, 1104,
-        "Redirection loop encountered while trying to fetch config JSON. Please contact us at https://configcat.com/support/");
+        $"Redirection loop encountered while trying to fetch config JSON. Please contact us at https://configcat.com/support/ (Ray ID: {FormatRayId(rayId)})",
+       "RAY_ID");
 
-    public static FormattableLogMessage FetchReceived200WithInvalidBody(this LoggerWrapper logger, Exception? ex) => logger.Log(
+    public static FormattableLogMessage FetchReceived200WithInvalidBody(this LoggerWrapper logger, string? rayId, Exception? ex) => logger.LogInterpolated(
         LogLevel.Error, 1105, ex,
-        "Fetching config JSON was successful but the HTTP response content was invalid.");
+        $"Fetching config JSON was successful but the HTTP response content was invalid. (Ray ID: {FormatRayId(rayId)})",
+        "RAY_ID");
 
-    public static FormattableLogMessage FetchReceived304WhenLocalCacheIsEmpty(this LoggerWrapper logger, int statusCode, string? reasonPhrase) => logger.LogInterpolated(
+    public static FormattableLogMessage FetchReceived304WhenLocalCacheIsEmpty(this LoggerWrapper logger, int statusCode, string? reasonPhrase, string? rayId) => logger.LogInterpolated(
         LogLevel.Error, 1106,
-        $"Unexpected HTTP response was received when no config JSON is cached locally: {statusCode} {reasonPhrase}",
-        "STATUS_CODE", "REASON_PHRASE");
+        $"Unexpected HTTP response was received when no config JSON is cached locally: {statusCode} {reasonPhrase} (Ray ID: {FormatRayId(rayId)})",
+        "STATUS_CODE", "REASON_PHRASE", "RAY_ID");
 
     public static FormattableLogMessage AutoPollConfigServiceErrorDuringPolling(this LoggerWrapper logger, Exception ex) => logger.Log(
         LogLevel.Error, 1200, ex,
@@ -194,4 +197,6 @@ public static FormattableLogMessage LocalFileDataSourceReloadsFile(this LoggerWr
     #region SDK-specific info messages (6000-6999)
 
     #endregion
+
+    internal static string FormatRayId(string? value) => value ?? "n/a";
 }