Add context.Context to HTTP middleware interface constructors (#14549)

#### Description

API change in extensionmiddleware, an unstable package to allow
middleware access to the start context.

HTTP only. gRPC is treated in #14536.

This is technically a breaking change in configmiddleware and for all
implementations of this extension. We believe no one is using this
feature outside of this repository, see memorylimiter is fixed here.

#### Link to tracking issue

Part of
#14523

#### Documentation

N/A

Author: jmacd

.chloggen/http-middlware-context.yaml

@@ -0,0 +1,9 @@
+change_type: bug_fix
+
+component: pkg/config/configmiddleware
+
+note: Add context.Context to HTTP middleware interface constructors. 
+
+subtext: This is a breaking API change for components that implement or use extensionmiddleware.
+
+issues: [14523]

config/confighttp/client.go

@@ -205,16 +205,15 @@ func (cc *ClientConfig) ToClient(ctx context.Context, extensions map[component.I
 		return nil, errors.New("middlewares were configured but this component or its host does not support extensions")
 	}
 	for i := len(cc.Middlewares) - 1; i >= 0; i-- {
-		var wrapper func(http.RoundTripper) (http.RoundTripper, error)
-		wrapper, err = cc.Middlewares[i].GetHTTPClientRoundTripper(ctx, extensions)
+		getClient, rerr := cc.Middlewares[i].GetHTTPClientRoundTripper(ctx, extensions)
 		// If we failed to get the middleware
-		if err != nil {
-			return nil, err
+		if rerr != nil {
+			return nil, rerr
 		}
-		clientTransport, err = wrapper(clientTransport)
+		clientTransport, rerr = getClient(ctx, clientTransport)
 		// If we failed to construct a wrapper
-		if err != nil {
-			return nil, err
+		if rerr != nil {
+			return nil, rerr
 		}
 	}
 

config/confighttp/client_middleware_test.go

@@ -32,30 +32,32 @@ type testClientMiddleware struct {
 func newTestClientMiddleware(name string) component.Component {
 	return &testClientMiddleware{
 		Extension: extensionmiddlewaretest.NewNop(),
-		GetHTTPRoundTripperFunc: func(transport http.RoundTripper) (http.RoundTripper, error) {
-			return extensionmiddlewaretest.RoundTripperFunc(
-				func(req *http.Request) (*http.Response, error) {
-					resp, err := transport.RoundTrip(req)
-					if err != nil {
-						return resp, err
-					}
-
-					// Read the original body
-					body, err := io.ReadAll(resp.Body)
-					if err != nil {
-						return resp, err
-					}
-					_ = resp.Body.Close()
-
-					// Create a new body with the appended text
-					newBody := string(body) + "\r\noutput by " + name
-
-					// Replace the response body
-					resp.Body = io.NopCloser(strings.NewReader(newBody))
-					resp.ContentLength = int64(len(newBody))
-
-					return resp, nil
-				}), nil
+		GetHTTPRoundTripperFunc: func(_ context.Context) (extensionmiddleware.WrapHTTPRoundTripperFunc, error) {
+			return func(_ context.Context, transport http.RoundTripper) (http.RoundTripper, error) {
+				return extensionmiddlewaretest.RoundTripperFunc(
+					func(req *http.Request) (*http.Response, error) {
+						resp, err := transport.RoundTrip(req)
+						if err != nil {
+							return resp, err
+						}
+
+						// Read the original body
+						body, err := io.ReadAll(resp.Body)
+						if err != nil {
+							return resp, err
+						}
+						_ = resp.Body.Close()
+
+						// Create a new body with the appended text
+						newBody := string(body) + "\r\noutput by " + name
+
+						// Replace the response body
+						resp.Body = io.NopCloser(strings.NewReader(newBody))
+						resp.ContentLength = int64(len(newBody))
+
+						return resp, nil
+					}), nil
+			}, nil
 		},
 	}
 }

config/confighttp/server.go

@@ -207,7 +207,7 @@ func (sc *ServerConfig) ToServer(ctx context.Context, extensions map[component.I
 		if err != nil {
 			return nil, err
 		}
-		handler, err = wrapper(handler)
+		handler, err = wrapper(ctx, handler)
 		// If we failed to construct a wrapper
 		if err != nil {
 			return nil, err

config/confighttp/server_middleware_test.go

@@ -32,17 +32,19 @@ type testServerMiddleware struct {
 func newTestServerMiddleware(name string) component.Component {
 	return &testServerMiddleware{
 		Extension: extensionmiddlewaretest.NewNop(),
-		GetHTTPHandlerFunc: func(handler http.Handler) (http.Handler, error) {
-			return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-				// Append middleware name to the URL path
-				r.URL.Path += name + "/"
+		GetHTTPHandlerFunc: func(_ context.Context) (extensionmiddleware.WrapHTTPHandlerFunc, error) {
+			return func(_ context.Context, handler http.Handler) (http.Handler, error) {
+				return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+					// Append middleware name to the URL path
+					r.URL.Path += name + "/"
 
-				// Call the next handler in the chain
-				handler.ServeHTTP(w, r)
+					// Call the next handler in the chain
+					handler.ServeHTTP(w, r)
 
-				// Add middleware name to the response
-				_, _ = w.Write([]byte("\r\nserved by " + name))
-			}), nil
+					// Add middleware name to the response
+					_, _ = w.Write([]byte("\r\nserved by " + name))
+				}), nil
+			}, nil
 		},
 	}
 }

config/configmiddleware/configmiddleware.go

@@ -9,7 +9,6 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"net/http"
 
 	"google.golang.org/grpc"
 
@@ -38,10 +37,10 @@ type Config struct {
 // returns the HTTP client wrapper function. If a middleware is not
 // found, an error is returned.  This should only be used by HTTP
 // clients.
-func (m Config) GetHTTPClientRoundTripper(_ context.Context, extensions map[component.ID]component.Component) (func(http.RoundTripper) (http.RoundTripper, error), error) {
+func (m Config) GetHTTPClientRoundTripper(ctx context.Context, extensions map[component.ID]component.Component) (extensionmiddleware.WrapHTTPRoundTripperFunc, error) {
 	if ext, found := extensions[m.ID]; found {
 		if client, ok := ext.(extensionmiddleware.HTTPClient); ok {
-			return client.GetHTTPRoundTripper, nil
+			return client.GetHTTPRoundTripper(ctx)
 		}
 		return nil, errNotHTTPClient
 	}
@@ -53,10 +52,10 @@ func (m Config) GetHTTPClientRoundTripper(_ context.Context, extensions map[comp
 // returns the http.Handler wrapper function. If a middleware is not
 // found, an error is returned.  This should only be used by HTTP
 // servers.
-func (m Config) GetHTTPServerHandler(_ context.Context, extensions map[component.ID]component.Component) (func(http.Handler) (http.Handler, error), error) {
+func (m Config) GetHTTPServerHandler(ctx context.Context, extensions map[component.ID]component.Component) (extensionmiddleware.WrapHTTPHandlerFunc, error) {
 	if ext, found := extensions[m.ID]; found {
 		if server, ok := ext.(extensionmiddleware.HTTPServer); ok {
-			return server.GetHTTPHandler, nil
+			return server.GetHTTPHandler(ctx)
 		}
 		return nil, errNotHTTPServer
 	}

extension/extensionmiddleware/client.go

@@ -12,8 +12,12 @@ import (
 
 // HTTPClient is an interface for HTTP client middleware extensions.
 type HTTPClient interface {
-	// GetHTTPRoundTripper wraps the provided client RoundTripper.
-	GetHTTPRoundTripper(http.RoundTripper) (http.RoundTripper, error)
+	// GetHTTPRoundTripper initializes a client HTTP RoundTripper
+	// wrapper, this typically called when the Collector
+	// starts. If there is an error this returns a nil
+	// function. If the error is nil, the WrapHTTPRoundTripperFunc
+	// will never be nil.
+	GetHTTPRoundTripper(context.Context) (WrapHTTPRoundTripperFunc, error)
 }
 
 // GRPCClient is an interface for gRPC client middleware extensions.
@@ -25,13 +29,13 @@ type GRPCClient interface {
 var _ HTTPClient = (*GetHTTPRoundTripperFunc)(nil)
 
 // GetHTTPRoundTripperFunc is a function that implements HTTPClient.
-type GetHTTPRoundTripperFunc func(base http.RoundTripper) (http.RoundTripper, error)
+type GetHTTPRoundTripperFunc func(context.Context) (WrapHTTPRoundTripperFunc, error)
 
-func (f GetHTTPRoundTripperFunc) GetHTTPRoundTripper(base http.RoundTripper) (http.RoundTripper, error) {
+func (f GetHTTPRoundTripperFunc) GetHTTPRoundTripper(ctx context.Context) (WrapHTTPRoundTripperFunc, error) {
 	if f == nil {
-		return base, nil
+		return func(_ context.Context, rt http.RoundTripper) (http.RoundTripper, error) { return rt, nil }, nil
 	}
-	return f(base)
+	return f(ctx)
 }
 
 var _ GRPCClient = (*GetGRPCClientOptionsFunc)(nil)
@@ -45,3 +49,7 @@ func (f GetGRPCClientOptionsFunc) GetGRPCClientOptions(ctx context.Context) ([]g
 	}
 	return f(ctx)
 }
+
+// WrapHTTPRoundTripperFunc is called to initialize a new instance of
+// HTTP client middleware.
+type WrapHTTPRoundTripperFunc = func(context.Context, http.RoundTripper) (http.RoundTripper, error)

extension/extensionmiddleware/client_test.go

@@ -16,33 +16,36 @@ import (
 func TestGetHTTPRoundTripperFunc(t *testing.T) {
 	// Create a base round tripper for testing
 	baseRT := http.DefaultTransport
+	testctx := context.Background()
 
 	t.Run("nil function", func(t *testing.T) {
 		var nilFunc GetHTTPRoundTripperFunc
-		rt, err := nilFunc.GetHTTPRoundTripper(baseRT)
+		rtfunc, err := nilFunc.GetHTTPRoundTripper(testctx)
+		require.NoError(t, err)
+
+		rt, err := rtfunc(testctx, baseRT)
 		require.NoError(t, err)
 		require.Equal(t, baseRT, rt)
 	})
 
 	t.Run("identity function", func(t *testing.T) {
-		identityFunc := GetHTTPRoundTripperFunc(func(base http.RoundTripper) (http.RoundTripper, error) {
-			return base, nil
-		})
-		rt, err := identityFunc.GetHTTPRoundTripper(baseRT)
+		identityFunc := GetHTTPRoundTripperFunc(nil)
+		rtfunc, err := identityFunc.GetHTTPRoundTripper(testctx)
+		require.NoError(t, err)
+		rt, err := rtfunc(testctx, baseRT)
 		require.NoError(t, err)
 		require.Equal(t, baseRT, rt)
 	})
 
 	t.Run("error function", func(t *testing.T) {
 		expectedErr := errors.New("round tripper error")
-		errorFunc := GetHTTPRoundTripperFunc(func(_ http.RoundTripper) (http.RoundTripper, error) {
+		errorFunc := GetHTTPRoundTripperFunc(func(_ context.Context) (WrapHTTPRoundTripperFunc, error) {
 			return nil, expectedErr
 		})
-
-		rt, err := errorFunc.GetHTTPRoundTripper(baseRT)
+		rtfunc, err := errorFunc.GetHTTPRoundTripper(testctx)
 		require.Error(t, err)
 		require.Equal(t, expectedErr, err)
-		require.Nil(t, rt)
+		require.Nil(t, rtfunc)
 	})
 }
 

extension/extensionmiddleware/extensionmiddlewaretest/err.go

@@ -5,7 +5,6 @@ package extensionmiddlewaretest // import "go.opentelemetry.io/collector/extensi
 
 import (
 	"context"
-	"net/http"
 
 	"google.golang.org/grpc"
 
@@ -35,13 +34,13 @@ type baseExtension struct {
 // extensionmiddleware interface and always returns an error.
 func NewErr(err error) extension.Extension {
 	return &baseExtension{
-		GetHTTPRoundTripperFunc: func(http.RoundTripper) (http.RoundTripper, error) {
+		GetHTTPRoundTripperFunc: func(context.Context) (extensionmiddleware.WrapHTTPRoundTripperFunc, error) {
 			return nil, err
 		},
 		GetGRPCClientOptionsFunc: func(context.Context) ([]grpc.DialOption, error) {
 			return nil, err
 		},
-		GetHTTPHandlerFunc: func(http.Handler) (http.Handler, error) {
+		GetHTTPHandlerFunc: func(context.Context) (extensionmiddleware.WrapHTTPHandlerFunc, error) {
 			return nil, err
 		},
 		GetGRPCServerOptionsFunc: func(context.Context) ([]grpc.ServerOption, error) {

extension/extensionmiddleware/extensionmiddlewaretest/err_test.go

@@ -18,7 +18,7 @@ func TestErrClient(t *testing.T) {
 
 	httpClient, ok := client.(extensionmiddleware.HTTPClient)
 	require.True(t, ok)
-	_, err := httpClient.GetHTTPRoundTripper(nil)
+	_, err := httpClient.GetHTTPRoundTripper(context.Background())
 	require.Error(t, err)
 
 	grpcClient, ok := client.(extensionmiddleware.GRPCClient)
@@ -29,10 +29,11 @@ func TestErrClient(t *testing.T) {
 
 func TestErrServer(t *testing.T) {
 	server := NewErr(errors.New("error"))
+	testctx := context.Background()
 
 	httpServer, ok := server.(extensionmiddleware.HTTPServer)
 	require.True(t, ok)
-	_, err := httpServer.GetHTTPHandler(nil)
+	_, err := httpServer.GetHTTPHandler(testctx)
 	require.Error(t, err)
 
 	grpcServer, ok := server.(extensionmiddleware.GRPCServer)