ThreeMammals · vijay-karavadra · Jul 13, 2025 · Jul 13, 2025 · Jul 13, 2025 · raman-m
diff --git a/src/Ocelot/Requester/SseDelegatingHandler.cs b/src/Ocelot/Requester/SseDelegatingHandler.cs
@@ -0,0 +1,64 @@
+using Microsoft.AspNetCore.Http;
+
+namespace Ocelot.Requester
+{
+    public class SseDelegatingHandler : DelegatingHandler
+    {
+        private readonly IHttpContextAccessor _httpContextAccessor;
+
+        public SseDelegatingHandler(IHttpContextAccessor httpContextAccessor)
+        {
+            _httpContextAccessor = httpContextAccessor;
+        }
+
+        protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
+        {
+            var httpContext = _httpContextAccessor.HttpContext;
+
+            var isSse = request.Headers.Accept.Any(h => h.MediaType == "text/event-stream");
+            if (!isSse)
+            {
+                return await base.SendAsync(request, cancellationToken);
+            }
+
+            // Correct overload: only 2 parameters
+            var response = await base.SendAsync(request, cancellationToken);
+
+            httpContext.Response.StatusCode = (int)response.StatusCode;
+            httpContext.Response.ContentType = "text/event-stream";
+
+            // Forward response headers
+            foreach (var header in response.Headers)
+            {
+                httpContext.Response.Headers[header.Key] = header.Value.ToArray();
+            }
+            foreach (var header in response.Content.Headers)
+            {
+                httpContext.Response.Headers[header.Key] = header.Value.ToArray();
+            }
+
+            httpContext.Response.Headers.Remove("transfer-encoding");
+
+            // Stream content
+            await using var downstreamStream = await response.Content.ReadAsStreamAsync(cancellationToken);
+            using var reader = new StreamReader(downstreamStream, Encoding.UTF8);
+
+            while (!reader.EndOfStream && !cancellationToken.IsCancellationRequested)
+            {
+                var line = await reader.ReadLineAsync();
+                if (line != null)
+                {
+                    var buffer = Encoding.UTF8.GetBytes(line + "\n");
+                    await httpContext.Response.Body.WriteAsync(buffer, 0, buffer.Length, cancellationToken);
+                    await httpContext.Response.Body.FlushAsync(cancellationToken);
+                }
+            }
+
+            // Dummy response to complete pipeline
+            return new HttpResponseMessage(response.StatusCode)
+            {
+                ReasonPhrase = "SSE stream has been forwarded"
+            };
+        }
+    }
+}
diff --git a/test/Ocelot.UnitTests/Requester/SseDelegatingHandlerTests.cs b/test/Ocelot.UnitTests/Requester/SseDelegatingHandlerTests.cs
@@ -0,0 +1,44 @@
+using Microsoft.AspNetCore.Http;
+using Moq.Protected;
+using Ocelot.Requester;
+
+namespace Ocelot.UnitTests.Requester
+{
+    public class SseDelegatingHandlerTests
+    {
+        [Fact]
+        public async Task SendAsync_ForNonSseRequest_CallsBaseHandler()
+        {
+            // Arrange
+            var mockHttpContext = new DefaultHttpContext();
+            var mockAccessor = new Mock<IHttpContextAccessor>();
+            mockAccessor.Setup(a => a.HttpContext).Returns(mockHttpContext);
+
+            var mockInnerHandler = new Mock<HttpMessageHandler>();
+            mockInnerHandler
+                .Protected()
+                .Setup<Task<HttpResponseMessage>>(
+                    "SendAsync",
+                    ItExpr.IsAny<HttpRequestMessage>(),
+                    ItExpr.IsAny<CancellationToken>())
+                .ReturnsAsync(new HttpResponseMessage(HttpStatusCode.OK));
+
+            var handler = new SseDelegatingHandler(mockAccessor.Object)
+            {
+                InnerHandler = mockInnerHandler.Object
+            };
+
+            var client = new HttpClient(handler);
+            var request = new HttpRequestMessage(HttpMethod.Get, "http://example.com");
+            request.Headers.Accept.Add(new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/json"));
+
+            // Act
+            var response = await client.SendAsync(request);
+
+            // Assert
+            Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+            mockInnerHandler.Protected().Verify("SendAsync", Times.Once(), ItExpr.IsAny<HttpRequestMessage>(), ItExpr.IsAny<CancellationToken>());
+        }
+    }
+
+}