Adding generated correlation id to response

sample/SampleWebApp/SampleWebApp.csproj

@@ -8,9 +8,12 @@
 
   <ItemGroup>
     <PackageReference Include="Serilog.AspNetCore" Version="8.0.2" />
-    <PackageReference Include="Serilog.Enrichers.ClientInfo" Version="2.1.1" />
     <PackageReference Include="Serilog.Sinks.Console" Version="6.0.0" />
     <PackageReference Include="Serilog.Sinks.File" Version="6.0.0" />
     <PackageReference Include="Swashbuckle.AspNetCore" Version="6.8.1" />
   </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\src\Serilog.Enrichers.ClientInfo\Serilog.Enrichers.ClientInfo.csproj" />
+  </ItemGroup>
 </Project>

sample/SampleWebApp/appsettings.json

@@ -31,7 +31,8 @@
       {
         "Name": "WithCorrelationId",
         "Args": {
-          "addValueIfHeaderAbsence": true
+          "addValueIfHeaderAbsence": true,
+          "addCorrelationIdToResponse": true
         }
       },
       {

src/Serilog.Enrichers.ClientInfo/Enrichers/CorrelationIdEnricher.cs

@@ -11,6 +11,7 @@ public class CorrelationIdEnricher : ILogEventEnricher
 {
     private const string CorrelationIdItemKey = "Serilog_CorrelationId";
     private const string PropertyName = "CorrelationId";
+    private readonly bool _addCorrelationIdToResponse;
     private readonly bool _addValueIfHeaderAbsence;
     private readonly IHttpContextAccessor _contextAccessor;
     private readonly string _headerKey;
@@ -24,15 +25,30 @@ public class CorrelationIdEnricher : ILogEventEnricher
     /// <param name="addValueIfHeaderAbsence">
     ///     Determines whether to add a new correlation ID value if the header is absent.
     /// </param>
-    public CorrelationIdEnricher(string headerKey, bool addValueIfHeaderAbsence)
-        : this(headerKey, addValueIfHeaderAbsence, new HttpContextAccessor())
+    /// <param name="addCorrelationIdToResponse">
+    ///     Determines whether to add correlation ID value to <see cref="HttpContext.Response" /> header collection.
+    /// </param>
+    public CorrelationIdEnricher(
+        string headerKey,
+        bool addValueIfHeaderAbsence,
+        bool addCorrelationIdToResponse)
+        : this(
+              headerKey,
+              addValueIfHeaderAbsence,
+              addCorrelationIdToResponse,
+              new HttpContextAccessor())
     {
     }
 
-    internal CorrelationIdEnricher(string headerKey, bool addValueIfHeaderAbsence, IHttpContextAccessor contextAccessor)
+    internal CorrelationIdEnricher(
+        string headerKey,
+        bool addValueIfHeaderAbsence,
+        bool addCorrelationIdToResponse,
+        IHttpContextAccessor contextAccessor)
     {
         _headerKey = headerKey;
         _addValueIfHeaderAbsence = addValueIfHeaderAbsence;
+        _addCorrelationIdToResponse = addCorrelationIdToResponse;
         _contextAccessor = contextAccessor;
     }
 
@@ -57,24 +73,47 @@ public void Enrich(LogEvent logEvent, ILogEventPropertyFactory propertyFactory)
             return;
         }
 
-        StringValues requestHeader = httpContext.Request.Headers[_headerKey];
-        StringValues responseHeader = httpContext.Response.Headers[_headerKey];
+        string correlationId = PrepareCorrelationId(httpContext);
 
-        string correlationId;
-
-        if (!string.IsNullOrWhiteSpace(requestHeader))
-            correlationId = requestHeader;
-        else if (!string.IsNullOrWhiteSpace(responseHeader))
-            correlationId = responseHeader;
-        else if (_addValueIfHeaderAbsence)
-            correlationId = Guid.NewGuid().ToString();
-        else
-            correlationId = null;
+        AddCorrelationIdToResponse(httpContext, correlationId);
 
         LogEventProperty correlationIdProperty = new(PropertyName, new ScalarValue(correlationId));
         logEvent.AddOrUpdateProperty(correlationIdProperty);
 
         httpContext.Items.Add(CorrelationIdItemKey, correlationIdProperty);
         httpContext.Items.Add(Constants.CorrelationIdValueKey, correlationId);
     }
+
+    private void AddCorrelationIdToResponse(HttpContext httpContext, string correlationId)
+    {
+        if (_addCorrelationIdToResponse
+            && !httpContext.Response.Headers.ContainsKey(_headerKey))
+        {
+            httpContext.Response.Headers[_headerKey] = correlationId;
+        }
+    }
+
+    private string PrepareCorrelationId(HttpContext httpContext)
+    {
+        StringValues requestHeader = httpContext.Request.Headers[_headerKey];
+
+        if (!string.IsNullOrWhiteSpace(requestHeader))
+        {
+            return requestHeader;
+        }
+
+        StringValues responseHeader = httpContext.Response.Headers[_headerKey];
+
+        if (!string.IsNullOrWhiteSpace(responseHeader))
+        {
+            return responseHeader;
+        }
+
+        if (_addValueIfHeaderAbsence)
+        {
+            return Guid.NewGuid().ToString();
+        }
+
+        return null;
+    }
 }

src/Serilog.Enrichers.ClientInfo/Extensions/ClientInfoLoggerConfigurationExtensions.cs

@@ -56,16 +56,20 @@ public static LoggerConfiguration WithClientIp(
     ///     Add generated correlation id value if correlation id header not available in
     ///     <see cref="HttpContext" /> header collection.
     /// </param>
+    /// <param name="addCorrelationIdToResponse">
+    ///     Add correlation id value to <see cref="HttpContext.Response" /> header collection.
+    /// </param>
     /// <exception cref="ArgumentNullException">enrichmentConfiguration</exception>
     /// <returns>The logger configuration so that multiple calls can be chained.</returns>
     public static LoggerConfiguration WithCorrelationId(
         this LoggerEnrichmentConfiguration enrichmentConfiguration,
         string headerName = "x-correlation-id",
-        bool addValueIfHeaderAbsence = false)
+        bool addValueIfHeaderAbsence = false,
+        bool addCorrelationIdToResponse = false)
     {
         ArgumentNullException.ThrowIfNull(enrichmentConfiguration, nameof(enrichmentConfiguration));
 
-        return enrichmentConfiguration.With(new CorrelationIdEnricher(headerName, addValueIfHeaderAbsence));
+        return enrichmentConfiguration.With(new CorrelationIdEnricher(headerName, addValueIfHeaderAbsence, addCorrelationIdToResponse));
     }
 
     /// <summary>

test/Serilog.Enrichers.ClientInfo.Tests/CorrelationIdEnricherTests.cs

@@ -26,31 +26,7 @@ public void EnrichLogWithCorrelationId_WhenHttpRequestContainCorrelationHeader_S
         // Arrange
         string correlationId = Guid.NewGuid().ToString();
         _contextAccessor.HttpContext!.Request!.Headers[HeaderKey] = correlationId;
-        CorrelationIdEnricher correlationIdEnricher = new(HeaderKey, false, _contextAccessor);
-
-        LogEvent evt = null;
-        Logger log = new LoggerConfiguration()
-            .Enrich.With(correlationIdEnricher)
-            .WriteTo.Sink(new DelegatingSink(e => evt = e))
-            .CreateLogger();
-
-        // Act
-        log.Information("Has a correlation id.");
-
-        // Assert
-        Assert.NotNull(evt);
-        Assert.True(evt.Properties.ContainsKey(LogPropertyName));
-        Assert.Equal(correlationId, evt.Properties[LogPropertyName].LiteralValue().ToString());
-    }
-
-    [Fact]
-    public void
-        EnrichLogWithCorrelationId_WhenHttpRequestContainCorrelationHeader_ShouldCreateCorrelationIdPropertyHasValue()
-    {
-        // Arrange
-        string correlationId = Guid.NewGuid().ToString();
-        _contextAccessor.HttpContext!.Request!.Headers[HeaderKey] = correlationId;
-        CorrelationIdEnricher correlationIdEnricher = new(HeaderKey, false, _contextAccessor);
+        CorrelationIdEnricher correlationIdEnricher = new(HeaderKey, false, true, _contextAccessor);
 
         LogEvent evt = null;
         Logger log = new LoggerConfiguration()
@@ -65,14 +41,15 @@ public void
         Assert.NotNull(evt);
         Assert.True(evt.Properties.ContainsKey(LogPropertyName));
         Assert.Equal(correlationId, evt.Properties[LogPropertyName].LiteralValue().ToString());
+        Assert.Equal(correlationId, _contextAccessor.HttpContext!.Response.Headers[HeaderKey]);
     }
 
     [Fact]
     public void
         EnrichLogWithCorrelationId_WhenHttpRequestNotContainCorrelationHeaderAndAddDefaultValueIsFalse_ShouldCreateCorrelationIdPropertyWithNoValue()
     {
         // Arrange
-        CorrelationIdEnricher correlationIdEnricher = new(HeaderKey, false, _contextAccessor);
+        CorrelationIdEnricher correlationIdEnricher = new(HeaderKey, false, false, _contextAccessor);
 
         LogEvent evt = null;
         Logger log = new LoggerConfiguration()
@@ -87,14 +64,15 @@ public void
         Assert.NotNull(evt);
         Assert.True(evt.Properties.ContainsKey(LogPropertyName));
         Assert.Null(evt.Properties[LogPropertyName].LiteralValue());
+        Assert.False(_contextAccessor.HttpContext!.Response.Headers.ContainsKey(HeaderKey));
     }
 
     [Fact]
     public void
         EnrichLogWithCorrelationId_WhenHttpRequestNotContainCorrelationHeaderAndAddDefaultValueIsTrue_ShouldCreateCorrelationIdPropertyHasValue()
     {
         // Arrange
-        CorrelationIdEnricher correlationIdEnricher = new(HeaderKey, true, _contextAccessor);
+        CorrelationIdEnricher correlationIdEnricher = new(HeaderKey, true, true, _contextAccessor);
 
         LogEvent evt = null;
         Logger log = new LoggerConfiguration()
@@ -109,6 +87,8 @@ public void
         Assert.NotNull(evt);
         Assert.True(evt.Properties.ContainsKey(LogPropertyName));
         Assert.NotNull(evt.Properties[LogPropertyName].LiteralValue().ToString());
+        Assert.NotNull(_contextAccessor.HttpContext!.Response.Headers[HeaderKey]);
+        Assert.Equal(evt.Properties[LogPropertyName].LiteralValue(), _contextAccessor.HttpContext!.Response.Headers[HeaderKey].ToString());
     }
 
     [Fact]
@@ -118,7 +98,7 @@ public void
         // Arrange
         string correlationId = Guid.NewGuid().ToString();
         _contextAccessor.HttpContext!.Request!.Headers[HeaderKey] = correlationId;
-        CorrelationIdEnricher correlationIdEnricher = new(HeaderKey, false, _contextAccessor);
+        CorrelationIdEnricher correlationIdEnricher = new(HeaderKey, false, true, _contextAccessor);
 
         LogEvent evt = null;
         Logger log = new LoggerConfiguration()
@@ -133,6 +113,7 @@ public void
         Assert.NotNull(evt);
         Assert.True(evt.Properties.ContainsKey(LogPropertyName));
         Assert.Equal(correlationId, evt.Properties[LogPropertyName].LiteralValue().ToString());
+        Assert.Equal(correlationId, _contextAccessor.HttpContext!.Response.Headers[HeaderKey]);
     }
 
     [Fact]
@@ -144,7 +125,7 @@ public void
         string responseCorrelationId = Guid.NewGuid().ToString();
         _contextAccessor.HttpContext!.Request!.Headers[HeaderKey] = requestCorrelationId;
         _contextAccessor.HttpContext!.Response!.Headers[HeaderKey] = responseCorrelationId;
-        CorrelationIdEnricher correlationIdEnricher = new(HeaderKey, false, _contextAccessor);
+        CorrelationIdEnricher correlationIdEnricher = new(HeaderKey, false, true, _contextAccessor);
 
         LogEvent evt = null;
         Logger log = new LoggerConfiguration()
@@ -159,6 +140,7 @@ public void
         Assert.NotNull(evt);
         Assert.True(evt.Properties.ContainsKey(LogPropertyName));
         Assert.Equal(requestCorrelationId, evt.Properties[LogPropertyName].LiteralValue().ToString());
+        Assert.Equal(responseCorrelationId, _contextAccessor.HttpContext!.Response.Headers[HeaderKey]);
     }
 
     [Fact]
@@ -167,7 +149,7 @@ public void GetCorrelationId_WhenHttpRequestContainCorrelationHeader_ShouldRetur
         // Arrange
         string correlationId = Guid.NewGuid().ToString();
         _contextAccessor.HttpContext!.Request!.Headers[HeaderKey] = correlationId;
-        CorrelationIdEnricher correlationIdEnricher = new(HeaderKey, false, _contextAccessor);
+        CorrelationIdEnricher correlationIdEnricher = new(HeaderKey, false, true, _contextAccessor);
 
         LogEvent evt = null;
         Logger log = new LoggerConfiguration()
@@ -182,14 +164,15 @@ public void GetCorrelationId_WhenHttpRequestContainCorrelationHeader_ShouldRetur
         // Assert
         Assert.NotNull(evt);
         Assert.Equal(correlationId, retrievedCorrelationId);
+        Assert.Equal(correlationId, _contextAccessor.HttpContext!.Response.Headers[HeaderKey]);
     }
 
     [Fact]
     public void
         GetCorrelationId_WhenHttpRequestNotContainCorrelationHeaderAndAddDefaultValueIsTrue_ShouldReturnGeneratedCorrelationIdFromHttpContext()
     {
         // Arrange
-        CorrelationIdEnricher correlationIdEnricher = new(HeaderKey, true, _contextAccessor);
+        CorrelationIdEnricher correlationIdEnricher = new(HeaderKey, true, true, _contextAccessor);
 
         LogEvent evt = null;
         Logger log = new LoggerConfiguration()
@@ -200,11 +183,13 @@ public void
         // Act
         log.Information("Has a correlation id.");
         string retrievedCorrelationId = _contextAccessor.HttpContext!.GetCorrelationId();
+        string correlationIdFromResponse = _contextAccessor.HttpContext!.Response.Headers[HeaderKey];
 
         // Assert
         Assert.NotNull(evt);
         Assert.NotNull(retrievedCorrelationId);
         Assert.NotEmpty(retrievedCorrelationId);
+        Assert.Equal(retrievedCorrelationId, correlationIdFromResponse);
         // Verify it's a valid GUID format
         Assert.True(Guid.TryParse(retrievedCorrelationId, out _));
     }
@@ -214,7 +199,7 @@ public void
         GetCorrelationId_WhenHttpRequestNotContainCorrelationHeaderAndAddDefaultValueIsFalse_ShouldReturnNullFromHttpContext()
     {
         // Arrange
-        CorrelationIdEnricher correlationIdEnricher = new(HeaderKey, false, _contextAccessor);
+        CorrelationIdEnricher correlationIdEnricher = new(HeaderKey, false, false, _contextAccessor);
 
         LogEvent evt = null;
         Logger log = new LoggerConfiguration()
@@ -229,6 +214,7 @@ public void
         // Assert
         Assert.NotNull(evt);
         Assert.Null(retrievedCorrelationId);
+        Assert.False(_contextAccessor.HttpContext!.Response.Headers.ContainsKey(HeaderKey));
     }
 
     [Fact]
@@ -237,7 +223,7 @@ public void GetCorrelationId_WhenCalledMultipleTimes_ShouldReturnSameCorrelation
         // Arrange
         string correlationId = Guid.NewGuid().ToString();
         _contextAccessor.HttpContext!.Request!.Headers[HeaderKey] = correlationId;
-        CorrelationIdEnricher correlationIdEnricher = new(HeaderKey, false, _contextAccessor);
+        CorrelationIdEnricher correlationIdEnricher = new(HeaderKey, false, false, _contextAccessor);
 
         Logger log = new LoggerConfiguration()
             .Enrich.With(correlationIdEnricher)
@@ -255,6 +241,7 @@ public void GetCorrelationId_WhenCalledMultipleTimes_ShouldReturnSameCorrelation
         Assert.Equal(correlationId, firstRetrieval);
         Assert.Equal(correlationId, secondRetrieval);
         Assert.Equal(firstRetrieval, secondRetrieval);
+        Assert.False(_contextAccessor.HttpContext!.Response.Headers.ContainsKey(HeaderKey));
     }
 
     [Fact]
@@ -273,7 +260,7 @@ public void EnrichLogWithCorrelationId_BackwardCompatibility_OldRetrievalMethodS
         // Arrange
         string correlationId = Guid.NewGuid().ToString();
         _contextAccessor.HttpContext!.Request!.Headers[HeaderKey] = correlationId;
-        CorrelationIdEnricher correlationIdEnricher = new(HeaderKey, false, _contextAccessor);
+        CorrelationIdEnricher correlationIdEnricher = new(HeaderKey, false, true, _contextAccessor);
 
         LogEvent evt = null;
         Logger log = new LoggerConfiguration()
@@ -300,6 +287,7 @@ public void EnrichLogWithCorrelationId_BackwardCompatibility_OldRetrievalMethodS
         Assert.Equal(correlationId, retrievedCorrelationIdOldWay);
         Assert.Equal(correlationId, retrievedCorrelationIdNewWay);
         Assert.Equal(retrievedCorrelationIdOldWay, retrievedCorrelationIdNewWay);
+        Assert.Equal(correlationId, _contextAccessor.HttpContext!.Response.Headers[HeaderKey]);
     }
 
     [Fact]