Write the HTTP response only when all output has been formatted #858

wedgberto · 2023-03-10T17:37:52Z

Purpose

This PR "buffers" the OData message wrapper in a memory stream until the OData query has been enumerated, then copies it into the HTTP response body only when no exception has been thrown.

Scenario

A WebAPI endpoint is serviced by an Entity Framework 6.0 IQueryable.

[HttpGet]
[EnableQuery]
public IQueryable<dto> Get()
{
    return this.dtoService.GetDtos();
}

When the SQL query is executed but the configured SQL command timeout is exceeded, our exception handling middleware successfully catches the SqlException, but is unable to set the HTTP status code to 500 because the HTTP response body is already started.

The endpoint returns a 200 OK HTTP status code and a body containing malformed JSON:

{"@odata.count":2,"value":[

wedgberto · 2023-03-10T17:43:03Z

This might resolve: #704

wedgberto · 2023-03-10T17:43:41Z

@microsoft-github-policy-service agree

Airex · 2023-03-10T18:14:24Z

src/Microsoft.AspNetCore.OData/Formatter/ODataOutputFormatterHelper.cs

@@ -150,6 +151,7 @@ public static ODataSerializerContext BuildSerializerContext(HttpRequest request)
 }

 await serializer.WriteObjectAsync(value, type, messageWriter, writeContext).ConfigureAwait(false);
+ await request.HttpContext.Response.Body.WriteAsync(responseBody.ToArray());


do we really need to create array of unknown size here?

i used responseBody.CopyTo(request.HttpContext.Response.Body) initially, but it didn't work how I expected so I resorted to this. I'll find a better way

Ha, I was missing rewinding the buffer response body stream back to position zero

Airex · 2023-03-10T18:14:59Z

src/Microsoft.AspNetCore.OData/Formatter/ODataOutputFormatterHelper.cs

@@ -67,19 +67,20 @@ public static ODataSerializerContext BuildSerializerContext(HttpRequest request)

 ODataPath path = request.ODataFeature().Path;
 IEdmNavigationSource targetNavigationSource = path.GetNavigationSource();
- HttpResponse response = request.HttpContext.Response;
+ var responseBody = new MemoryStream();


Assume to use memory stream pooling

Do you mean Microsoft.IO.RecyclableMemoryStream ?

mikepizzo

@wedgberto -- thanks for your contribution!

Note that we do not want to buffer in memory by default -- this can have a significant performance impact for large responses, and we do everything possible to make sure that we are able to stream a response without buffering.

In order to support efficient streaming, the OData protocol specifically describes instream error scenarios, calling for the response body to be malformed JSON.

wedgberto · 2023-03-17T16:33:59Z

@wedgberto -- thanks for your contribution!

Note that we do not want to buffer in memory by default -- this can have a significant performance impact for large responses, and we do everything possible to make sure that we are able to stream a response without buffering.

In order to support efficient streaming, the OData protocol specifically describes instream error scenarios, calling for the response body to be malformed JSON.

So rather than return an appropriate HTTP error status code, the spec states to return a 200 OK with a malformed JSON response body. If that is the case then I guess this PR is obsolete and can be aborted. We'll just have to code our Angular consumer to compensate and not assume that 200 OK responses contain valid JSON.

There are other issues in this repo that mention incomplete JSON in the response that might find this specified behaviour useful. #760 #219 #109

wachugamaina · 2024-03-08T13:26:00Z

src/Microsoft.AspNetCore.OData/Formatter/ODataOutputFormatterHelper.cs

@@ -21,6 +21,7 @@
 using Microsoft.AspNetCore.OData.Formatter.Value;


Could we add a test for this functionality ?

David Wedgbury added 2 commits March 10, 2023 17:12

Write the HTTP response only when all output has been formatted

4097210

Remove commented code

9a6ac6c

Airex reviewed Mar 10, 2023

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David Wedgbury added 2 commits March 13, 2023 17:41

Copy buffer stream to response stream more efficiently

6d61c52

Use pooled memory stream

b17ad17

wedgberto requested a review from Airex March 14, 2023 16:34

mikepizzo requested changes Mar 16, 2023

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wachugamaina reviewed Mar 8, 2024

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Write the HTTP response only when all output has been formatted #858

Write the HTTP response only when all output has been formatted #858

wedgberto commented Mar 10, 2023

wedgberto commented Mar 10, 2023

wedgberto commented Mar 10, 2023

Airex Mar 10, 2023

wedgberto Mar 10, 2023 •

edited

wedgberto Mar 11, 2023

Airex Mar 10, 2023

wedgberto Mar 10, 2023

mikepizzo left a comment •

edited

wedgberto commented Mar 17, 2023 •

edited

wachugamaina Mar 8, 2024

		@@ -21,6 +21,7 @@
		using Microsoft.AspNetCore.OData.Formatter.Value;

Write the HTTP response only when all output has been formatted #858

Are you sure you want to change the base?

Write the HTTP response only when all output has been formatted #858

Conversation

wedgberto commented Mar 10, 2023

Purpose

Scenario

wedgberto commented Mar 10, 2023

wedgberto commented Mar 10, 2023

Airex Mar 10, 2023

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wedgberto Mar 10, 2023 • edited

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wedgberto commented Mar 17, 2023 • edited

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wedgberto Mar 10, 2023 •

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wedgberto commented Mar 17, 2023 •

edited