Class HttpTransformer

Inheritance
System.Object
HttpTransformer
Namespace: Yarp.ReverseProxy.Forwarder
Assembly: Yarp.ReverseProxy.dll
Syntax
public class HttpTransformer : object

Constructors

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HttpTransformer()

Used to create derived instances.

Declaration
protected HttpTransformer()

Fields

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Default

A default set of transforms that adds X-Forwarded-* headers, removes the original Host value and copies all other request and response fields and headers, except for some protocol specific values.

Declaration
public static readonly HttpTransformer Default
Field Value
Type Description
HttpTransformer
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Empty

An empty transformer that copies all request and response fields and headers, except for some protocol specific values.

Declaration
public static readonly HttpTransformer Empty
Field Value
Type Description
HttpTransformer

Methods

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TransformRequestAsync(HttpContext, HttpRequestMessage, String)

A callback that is invoked prior to sending the proxied request. All HttpRequestMessage fields are initialized except RequestUri, which will be initialized after the callback if no value is provided. See MakeDestinationAddress(String, PathString, QueryString) for constructing a custom request Uri. The string parameter represents the destination URI prefix that should be used when constructing the RequestUri. The headers are copied by the base implementation, excluding some protocol headers like HTTP/2 pseudo headers (":authority"). This method may be overridden to conditionally produce a response, such as for error conditions, and prevent the request from being proxied. This is indicated by setting the HttpResponse.StatusCode to a value other than 200, or calling HttpResponse.StartAsync(), or writing to the HttpResponse.Body or BodyWriter.

Declaration
public virtual ValueTask TransformRequestAsync(HttpContext httpContext, HttpRequestMessage proxyRequest, string destinationPrefix)
Parameters
Type Name Description
HttpContext httpContext

The incoming request.
HttpRequestMessage proxyRequest

The outgoing proxy request.
System.String destinationPrefix

The uri prefix for the selected destination server which can be used to create the RequestUri.
Returns
Type Description
ValueTask
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TransformRequestAsync(HttpContext, HttpRequestMessage, String, CancellationToken)

A callback that is invoked prior to sending the proxied request. All HttpRequestMessage fields are initialized except RequestUri, which will be initialized after the callback if no value is provided. See MakeDestinationAddress(String, PathString, QueryString) for constructing a custom request Uri. The string parameter represents the destination URI prefix that should be used when constructing the RequestUri. The headers are copied by the base implementation, excluding some protocol headers like HTTP/2 pseudo headers (":authority"). This method may be overridden to conditionally produce a response, such as for error conditions, and prevent the request from being proxied. This is indicated by setting the HttpResponse.StatusCode to a value other than 200, or calling HttpResponse.StartAsync(), or writing to the HttpResponse.Body or BodyWriter.

Declaration
public virtual ValueTask TransformRequestAsync(HttpContext httpContext, HttpRequestMessage proxyRequest, string destinationPrefix, CancellationToken cancellationToken)
Parameters
Type Name Description
HttpContext httpContext

The incoming request.
HttpRequestMessage proxyRequest

The outgoing proxy request.
System.String destinationPrefix

The uri prefix for the selected destination server which can be used to create the RequestUri.
CancellationToken cancellationToken

Indicates that the request is being canceled.
Returns
Type Description
ValueTask
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TransformResponseAsync(HttpContext, Nullable<HttpResponseMessage>)

A callback that is invoked when the proxied response is received. The status code and reason phrase will be copied to the HttpContext.Response before the callback is invoked, but may still be modified there. The headers will be copied to HttpContext.Response.Headers by the base implementation, excludes certain protocol headers like Transfer-Encoding: chunked.

Declaration
public virtual ValueTask<bool> TransformResponseAsync(HttpContext httpContext, HttpResponseMessage? proxyResponse)
Parameters
Type Name Description
HttpContext httpContext

The incoming request.
System.Nullable<HttpResponseMessage> proxyResponse

The response from the destination. This can be null if the destination did not respond.
Returns
Type Description
ValueTask<System.Boolean>

A bool indicating if the response should be proxied to the client or not. A derived implementation that returns false may send an alternate response inline or return control to the caller for it to retry, respond, etc.
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TransformResponseAsync(HttpContext, Nullable<HttpResponseMessage>, CancellationToken)

A callback that is invoked when the proxied response is received. The status code and reason phrase will be copied to the HttpContext.Response before the callback is invoked, but may still be modified there. The headers will be copied to HttpContext.Response.Headers by the base implementation, excludes certain protocol headers like Transfer-Encoding: chunked.

Declaration
public virtual ValueTask<bool> TransformResponseAsync(HttpContext httpContext, HttpResponseMessage? proxyResponse, CancellationToken cancellationToken)
Parameters
Type Name Description
HttpContext httpContext

The incoming request.
System.Nullable<HttpResponseMessage> proxyResponse

The response from the destination. This can be null if the destination did not respond.
CancellationToken cancellationToken

Indicates that the request is being canceled.
Returns
Type Description
ValueTask<System.Boolean>

A bool indicating if the response should be proxied to the client or not. A derived implementation that returns false may send an alternate response inline or return control to the caller for it to retry, respond, etc.
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TransformResponseTrailersAsync(HttpContext, HttpResponseMessage)

A callback that is invoked after the response body to modify trailers, if supported. The trailers will be copied to the HttpContext.Response by the base implementation.

Declaration
public virtual ValueTask TransformResponseTrailersAsync(HttpContext httpContext, HttpResponseMessage proxyResponse)
Parameters
Type Name Description
HttpContext httpContext

The incoming request.
HttpResponseMessage proxyResponse

The response from the destination.
Returns
Type Description
ValueTask
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TransformResponseTrailersAsync(HttpContext, HttpResponseMessage, CancellationToken)

A callback that is invoked after the response body to modify trailers, if supported. The trailers will be copied to the HttpContext.Response by the base implementation.

Declaration
public virtual ValueTask TransformResponseTrailersAsync(HttpContext httpContext, HttpResponseMessage proxyResponse, CancellationToken cancellationToken)
Parameters
Type Name Description
HttpContext httpContext

The incoming request.
HttpResponseMessage proxyResponse

The response from the destination.
CancellationToken cancellationToken

Indicates that the request is being canceled.
Returns
Type Description
ValueTask