48 lines
1.9 KiB
Go
48 lines
1.9 KiB
Go
// +build go1.11
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package middleware
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import (
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"context"
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"fmt"
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"net/http"
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"net/http/httputil"
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"strings"
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"github.com/labstack/echo/v4"
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)
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// StatusCodeContextCanceled is a custom HTTP status code for situations
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// where a client unexpectedly closed the connection to the server.
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// As there is no standard error code for "client closed connection", but
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// various well-known HTTP clients and server implement this HTTP code we use
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// 499 too instead of the more problematic 5xx, which does not allow to detect this situation
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const StatusCodeContextCanceled = 499
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func proxyHTTP(tgt *ProxyTarget, c echo.Context, config ProxyConfig) http.Handler {
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proxy := httputil.NewSingleHostReverseProxy(tgt.URL)
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proxy.ErrorHandler = func(resp http.ResponseWriter, req *http.Request, err error) {
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desc := tgt.URL.String()
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if tgt.Name != "" {
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desc = fmt.Sprintf("%s(%s)", tgt.Name, tgt.URL.String())
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}
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// If the client canceled the request (usually by closing the connection), we can report a
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// client error (4xx) instead of a server error (5xx) to correctly identify the situation.
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// The Go standard library (at of late 2020) wraps the exported, standard
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// context.Canceled error with unexported garbage value requiring a substring check, see
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// https://github.com/golang/go/blob/6965b01ea248cabb70c3749fd218b36089a21efb/src/net/net.go#L416-L430
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if err == context.Canceled || strings.Contains(err.Error(), "operation was canceled") {
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httpError := echo.NewHTTPError(StatusCodeContextCanceled, fmt.Sprintf("client closed connection: %v", err))
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httpError.Internal = err
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c.Set("_error", httpError)
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} else {
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httpError := echo.NewHTTPError(http.StatusBadGateway, fmt.Sprintf("remote %s unreachable, could not forward: %v", desc, err))
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httpError.Internal = err
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c.Set("_error", httpError)
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}
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}
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proxy.Transport = config.Transport
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proxy.ModifyResponse = config.ModifyResponse
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return proxy
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}
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