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Avoid an async state machine allocation from CopyResponseBodyAsync #2586

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merged 1 commit into from
Aug 27, 2024
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Avoid an async state machine allocation from CopyResponseBodyAsync #2586

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26 changes: 8 additions & 18 deletions src/ReverseProxy/Forwarder/HttpForwarder.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -277,7 +277,14 @@ public async ValueTask<ForwarderError> SendAsync(
// and clients misbehave if the initial headers response does not indicate stream end.

// :: Step 7-B: Copy response body Client ◄-- Proxy ◄-- Destination
var (responseBodyCopyResult, responseBodyException) = await CopyResponseBodyAsync(destinationResponse.Content, context.Response.Body, activityCancellationSource);
StreamCopyResult responseBodyCopyResult;
Exception? responseBodyException;

using (var destinationResponseStream = await destinationResponse.Content.ReadAsStreamAsync(activityCancellationSource.Token))
{
// The response content-length is enforced by the server.
(responseBodyCopyResult, responseBodyException) = await StreamCopier.CopyAsync(isRequest: false, destinationResponseStream, context.Response.Body, StreamCopier.UnknownLength, _timeProvider, activityCancellationSource, activityCancellationSource.Token);
}

if (responseBodyCopyResult != StreamCopyResult.Success)
{
Expand Down Expand Up @@ -875,23 +882,6 @@ private ForwarderError FixupUpgradeResponseHeaders(HttpContext context, HttpResp
return ForwarderError.None;
}

private async ValueTask<(StreamCopyResult, Exception?)> CopyResponseBodyAsync(HttpContent destinationResponseContent, Stream clientResponseStream,
ActivityCancellationTokenSource activityCancellationSource)
{
// SocketHttpHandler and similar transports always provide an HttpContent object, even if it's empty.
// In 3.1 this is only likely to return null in tests.
// As of 5.0 HttpResponse.Content never returns null.
// https://github.com/dotnet/runtime/blame/8fc68f626a11d646109a758cb0fc70a0aa7826f1/src/libraries/System.Net.Http/src/System/Net/Http/HttpResponseMessage.cs#L46
if (destinationResponseContent is not null)
{
using var destinationResponseStream = await destinationResponseContent.ReadAsStreamAsync(activityCancellationSource.Token);
// The response content-length is enforced by the server.
return await StreamCopier.CopyAsync(isRequest: false, destinationResponseStream, clientResponseStream, StreamCopier.UnknownLength, _timeProvider, activityCancellationSource, activityCancellationSource.Token);
}

return (StreamCopyResult.Success, null);
}

private async ValueTask<ForwarderError> HandleResponseBodyErrorAsync(HttpContext context, StreamCopyHttpContent? requestContent, StreamCopyResult responseBodyCopyResult, Exception responseBodyException, ActivityCancellationTokenSource requestCancellationSource)
{
if (requestContent is not null && requestContent.Started)
Expand Down