From 30f4bc11379fad311537db216f7b7171a89e00fe Mon Sep 17 00:00:00 2001
From: Joshua MacDonald <josh.macdonald@gmail.com>
Date: Mon, 14 Apr 2025 17:59:36 -0700
Subject: [PATCH 01/13] Middleware: HTTP support (part 3/4)

---
 .chloggen/middleware-http.yaml              |  25 +++
 config/confighttp/README.md                 |   2 +
 config/confighttp/client_middleware_test.go | 159 ++++++++++++++++++++
 config/confighttp/confighttp.go             |  45 +++++-
 config/confighttp/go.mod                    |   6 +
 config/confighttp/server_middleware_test.go | 138 +++++++++++++++++
 config/confighttp/xconfighttp/go.mod        |   6 +
 7 files changed, 380 insertions(+), 1 deletion(-)
 create mode 100644 .chloggen/middleware-http.yaml
 create mode 100644 config/confighttp/client_middleware_test.go
 create mode 100644 config/confighttp/server_middleware_test.go

diff --git a/.chloggen/middleware-http.yaml b/.chloggen/middleware-http.yaml
new file mode 100644
index 00000000000..a16d7b41323
--- /dev/null
+++ b/.chloggen/middleware-http.yaml
@@ -0,0 +1,25 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. otlpreceiver)
+component: configmiddleware
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add HTTP middleware support.
+
+# One or more tracking issues or pull requests related to the change
+issues: [12603, 9591]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [user]
diff --git a/config/confighttp/README.md b/config/confighttp/README.md
index 1f1cb1bba27..1ee56939814 100644
--- a/config/confighttp/README.md
+++ b/config/confighttp/README.md
@@ -58,6 +58,7 @@ README](../configtls/README.md).
 - [`http2_ping_timeout`](https://pkg.go.dev/golang.org/x/net/http2#Transport)
 - [`cookies`](https://pkg.go.dev/net/http#CookieJar)
   - [`enabled`] if enabled, the client will store cookies from server responses and reuse them in subsequent requests.
+- [`middlewares`](../configmiddleware/README.md)
 
 Example:
 
@@ -107,6 +108,7 @@ will not be enabled.
 - [`tls`](../configtls/README.md)
 - [`auth`](../configauth/README.md)
   - `request_params`: a list of query parameter names to add to the auth context, along with the HTTP headers
+- [`middlewares`](../configmiddleware/README.md)
 
 You can enable [`attribute processor`][attribute-processor] to append any http header to span's attribute using custom key. You also need to enable the "include_metadata"
 
diff --git a/config/confighttp/client_middleware_test.go b/config/confighttp/client_middleware_test.go
new file mode 100644
index 00000000000..a5424897d7e
--- /dev/null
+++ b/config/confighttp/client_middleware_test.go
@@ -0,0 +1,159 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package confighttp
+
+import (
+	"context"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"go.opentelemetry.io/collector/component"
+	"go.opentelemetry.io/collector/component/componenttest"
+	"go.opentelemetry.io/collector/config/configmiddleware"
+	"go.opentelemetry.io/collector/extension/extensionmiddleware"
+)
+
+// testClientMiddleware is a test middleware that appends a string to the response body
+type testClientMiddleware struct {
+	name string
+}
+
+func (*testClientMiddleware) Start(_ context.Context, _ component.Host) error {
+	return nil
+}
+
+func (*testClientMiddleware) Shutdown(_ context.Context) error {
+	return nil
+}
+
+var _ extensionmiddleware.HTTPClient = &testClientMiddleware{}
+
+// GetHTTPRoundTripper creates a round tripper that appends text to the response body
+func (m *testClientMiddleware) GetHTTPRoundTripper(transport http.RoundTripper) (http.RoundTripper, error) {
+	return &bodyAppenderRoundTripper{
+		name:      m.name,
+		transport: transport,
+	}, nil
+}
+
+// bodyAppenderRoundTripper is a round tripper that appends text to the response body
+type bodyAppenderRoundTripper struct {
+	name      string
+	transport http.RoundTripper
+}
+
+// RoundTrip appends text to the response body
+func (rt *bodyAppenderRoundTripper) RoundTrip(req *http.Request) (*http.Response, error) {
+	resp, err := rt.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 " + rt.name
+
+	// Replace the response body
+	resp.Body = io.NopCloser(strings.NewReader(newBody))
+	resp.ContentLength = int64(len(newBody))
+
+	return resp, nil
+}
+
+func newTestClientMiddleware(name string) component.Component {
+	return &testClientMiddleware{
+		name: name,
+	}
+}
+
+func newTestClientConfig(name string) configmiddleware.Middleware {
+	return configmiddleware.Middleware{
+		MiddlewareID: component.MustNewID(name),
+	}
+}
+
+func TestClientMiddlewares(t *testing.T) {
+	// Create a test server that returns "OK"
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		_, _ = w.Write([]byte("OK"))
+	}))
+	defer server.Close()
+
+	// Register two test extensions
+	host := &mockHost{
+		ext: map[component.ID]component.Component{
+			component.MustNewID("test1"): newTestClientMiddleware("test1"),
+			component.MustNewID("test2"): newTestClientMiddleware("test2"),
+		},
+	}
+
+	// Test with different middleware configurations
+	testCases := []struct {
+		name           string
+		middlewares    []configmiddleware.Middleware
+		expectedOutput string
+	}{
+		{
+			name:           "no_middlewares",
+			middlewares:    nil,
+			expectedOutput: "OK",
+		},
+		{
+			name: "single_middleware",
+			middlewares: []configmiddleware.Middleware{
+				newTestClientConfig("test1"),
+			},
+			expectedOutput: "OK\r\noutput by test1",
+		},
+		{
+			name: "multiple_middlewares",
+			middlewares: []configmiddleware.Middleware{
+				newTestClientConfig("test1"),
+				newTestClientConfig("test2"),
+			},
+			expectedOutput: "OK\r\noutput by test2\r\noutput by test1",
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			// Create HTTP client config with the test middlewares
+			clientConfig := ClientConfig{
+				Endpoint:    server.URL,
+				Middlewares: tc.middlewares,
+			}
+
+			// Create the client
+			client, err := clientConfig.ToClient(context.Background(), host, componenttest.NewNopTelemetrySettings())
+			require.NoError(t, err)
+
+			// Create a request to the test server
+			req, err := http.NewRequest(http.MethodGet, server.URL, nil)
+			require.NoError(t, err)
+
+			// Send the request
+			resp, err := client.Do(req)
+			require.NoError(t, err)
+			defer resp.Body.Close()
+
+			// Check the response
+			body, err := io.ReadAll(resp.Body)
+			require.NoError(t, err)
+			assert.Equal(t, tc.expectedOutput, string(body))
+		})
+	}
+}
diff --git a/config/confighttp/confighttp.go b/config/confighttp/confighttp.go
index 43193c957ee..1d8f8b68c48 100644
--- a/config/confighttp/confighttp.go
+++ b/config/confighttp/confighttp.go
@@ -27,6 +27,7 @@ import (
 	"go.opentelemetry.io/collector/config/configauth"
 	"go.opentelemetry.io/collector/config/configcompression"
 	"go.opentelemetry.io/collector/config/confighttp/internal"
+	"go.opentelemetry.io/collector/config/configmiddleware"
 	"go.opentelemetry.io/collector/config/configopaque"
 	"go.opentelemetry.io/collector/config/configtls"
 	"go.opentelemetry.io/collector/extension/extensionauth"
@@ -111,6 +112,11 @@ type ClientConfig struct {
 	HTTP2PingTimeout time.Duration `mapstructure:"http2_ping_timeout,omitempty"`
 	// Cookies configures the cookie management of the HTTP client.
 	Cookies *CookiesConfig `mapstructure:"cookies,omitempty"`
+
+	// Middlewares are used to add custom functionality to the HTTP client.
+	// Middleware handlers are applied in the order they appear in this list,
+	// with the first middleware becoming the outermost handler.
+	Middlewares []configmiddleware.Middleware `mapstructure:"middleware,omitempty"`
 }
 
 // CookiesConfig defines the configuration of the HTTP client regarding cookies served by the server.
@@ -194,6 +200,22 @@ func (hcs *ClientConfig) ToClient(ctx context.Context, host component.Host, sett
 
 	clientTransport := (http.RoundTripper)(transport)
 
+	// Apply middlewares in reverse order so they are applied in
+	// order. The first middleware runs after authentication.
+	for i := len(hcs.Middlewares) - 1; i >= 0; i-- {
+		var wrapper func(http.RoundTripper) (http.RoundTripper, error)
+		wrapper, err = hcs.Middlewares[i].GetHTTPClientRoundTripper(ctx, host.GetExtensions())
+		// If we failed to get the middleware
+		if err != nil {
+			return nil, err
+		}
+		clientTransport, err = wrapper(clientTransport)
+		// If we failed to construct a wrapper
+		if err != nil {
+			return nil, err
+		}
+	}
+
 	// The Auth RoundTripper should always be the innermost to ensure that
 	// request signing-based auth mechanisms operate after compression
 	// and header middleware modifies the request
@@ -338,6 +360,11 @@ type ServerConfig struct {
 	// is zero, the value of ReadTimeout is used. If both are
 	// zero, there is no timeout.
 	IdleTimeout time.Duration `mapstructure:"idle_timeout"`
+
+	// Middlewares are used to add custom functionality to the HTTP server.
+	// Middleware handlers are applied in the order they appear in this list,
+	// with the first middleware becoming the outermost handler.
+	Middlewares []configmiddleware.Middleware `mapstructure:"middleware,omitempty"`
 }
 
 // NewDefaultServerConfig returns ServerConfig type object with default values.
@@ -411,7 +438,7 @@ func WithDecoder(key string, dec func(body io.ReadCloser) (io.ReadCloser, error)
 }
 
 // ToServer creates an http.Server from settings object.
-func (hss *ServerConfig) ToServer(_ context.Context, host component.Host, settings component.TelemetrySettings, handler http.Handler, opts ...ToServerOption) (*http.Server, error) {
+func (hss *ServerConfig) ToServer(ctx context.Context, host component.Host, settings component.TelemetrySettings, handler http.Handler, opts ...ToServerOption) (*http.Server, error) {
 	serverOpts := &toServerOptions{}
 	serverOpts.Apply(opts...)
 
@@ -423,6 +450,22 @@ func (hss *ServerConfig) ToServer(_ context.Context, host component.Host, settin
 		hss.CompressionAlgorithms = defaultCompressionAlgorithms
 	}
 
+	// Apply middlewares in reverse order so they are applied in
+	// order.  The first middleware runs after decompression,
+	// below, preceded by Auth, CORS, etc.
+	for i := len(hss.Middlewares) - 1; i >= 0; i-- {
+		wrapper, err := hss.Middlewares[i].GetHTTPServerHandler(ctx, host.GetExtensions())
+		// If we failed to get the middleware
+		if err != nil {
+			return nil, err
+		}
+		handler, err = wrapper(handler)
+		// If we failed to construct a wrapper
+		if err != nil {
+			return nil, err
+		}
+	}
+
 	handler = httpContentDecompressor(
 		handler,
 		hss.MaxRequestBodySize,
diff --git a/config/confighttp/go.mod b/config/confighttp/go.mod
index 2b596b18edf..c9f28edf027 100644
--- a/config/confighttp/go.mod
+++ b/config/confighttp/go.mod
@@ -13,11 +13,13 @@ require (
 	go.opentelemetry.io/collector/component/componenttest v0.124.0
 	go.opentelemetry.io/collector/config/configauth v0.124.0
 	go.opentelemetry.io/collector/config/configcompression v1.30.0
+	go.opentelemetry.io/collector/config/configmiddleware v0.0.0-00010101000000-000000000000
 	go.opentelemetry.io/collector/config/configopaque v1.30.0
 	go.opentelemetry.io/collector/config/configtls v1.30.0
 	go.opentelemetry.io/collector/extension v1.30.0
 	go.opentelemetry.io/collector/extension/extensionauth v1.30.0
 	go.opentelemetry.io/collector/extension/extensionauth/extensionauthtest v0.124.0
+	go.opentelemetry.io/collector/extension/extensionmiddleware v0.0.0-00010101000000-000000000000
 	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.60.0
 	go.opentelemetry.io/otel v1.35.0
 	go.uber.org/goleak v1.3.0
@@ -58,6 +60,8 @@ replace go.opentelemetry.io/collector/config/configauth => ../configauth
 
 replace go.opentelemetry.io/collector/config/configcompression => ../configcompression
 
+replace go.opentelemetry.io/collector/config/configmiddleware => ../configmiddleware
+
 replace go.opentelemetry.io/collector/config/configopaque => ../configopaque
 
 replace go.opentelemetry.io/collector/config/configtls => ../configtls
@@ -66,6 +70,8 @@ replace go.opentelemetry.io/collector/extension => ../../extension
 
 replace go.opentelemetry.io/collector/extension/extensionauth => ../../extension/extensionauth
 
+replace go.opentelemetry.io/collector/extension/extensionmiddleware => ../../extension/extensionmiddleware
+
 replace go.opentelemetry.io/collector/pdata => ../../pdata
 
 replace go.opentelemetry.io/collector/component => ../../component
diff --git a/config/confighttp/server_middleware_test.go b/config/confighttp/server_middleware_test.go
new file mode 100644
index 00000000000..bc9c2ebec7a
--- /dev/null
+++ b/config/confighttp/server_middleware_test.go
@@ -0,0 +1,138 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package confighttp
+
+import (
+	"context"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"go.opentelemetry.io/collector/component"
+	"go.opentelemetry.io/collector/component/componenttest"
+	"go.opentelemetry.io/collector/config/configmiddleware"
+)
+
+// testServerMiddleware is a test implementation of configmiddleware.Middleware
+type testServerMiddleware struct {
+	name string
+}
+
+func (*testServerMiddleware) Start(_ context.Context, _ component.Host) error {
+	return nil
+}
+
+func (*testServerMiddleware) Shutdown(_ context.Context) error {
+	return nil
+}
+
+func (tm *testServerMiddleware) GetHTTPHandler(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 += tm.name + "/"
+
+		// Call the next handler in the chain
+		handler.ServeHTTP(w, r)
+
+		// Add middleware name to the response
+		_, _ = w.Write([]byte("\r\nserved by " + tm.name))
+	}), nil
+}
+
+func newTestServerMiddleware(name string) component.Component {
+	return &testServerMiddleware{
+		name: name,
+	}
+}
+
+func newTestServerConfig(name string) configmiddleware.Middleware {
+	return configmiddleware.Middleware{
+		MiddlewareID: component.MustNewID(name),
+	}
+}
+
+func TestServerMiddleware(t *testing.T) {
+	// Register two test extensions
+	host := &mockHost{
+		ext: map[component.ID]component.Component{
+			component.MustNewID("test1"): newTestServerMiddleware("test1"),
+			component.MustNewID("test2"): newTestServerMiddleware("test2"),
+		},
+	}
+
+	// Test with different middleware configurations
+	testCases := []struct {
+		name           string
+		middlewares    []configmiddleware.Middleware
+		expectedOutput string
+	}{
+		{
+			name:           "no_middlewares",
+			middlewares:    nil,
+			expectedOutput: "OK{/}",
+		},
+		{
+			name: "single_middleware",
+			middlewares: []configmiddleware.Middleware{
+				newTestServerConfig("test1"),
+			},
+			expectedOutput: "OK{/test1/}\r\nserved by test1",
+		},
+		{
+			name: "multiple_middlewares",
+			middlewares: []configmiddleware.Middleware{
+				newTestServerConfig("test1"),
+				newTestServerConfig("test2"),
+			},
+			expectedOutput: "OK{/test1/test2/}\r\nserved by test2\r\nserved by test1",
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			// Create server config with the test middlewares
+			cfg := ServerConfig{
+				Endpoint:    "localhost:0",
+				Middlewares: tc.middlewares,
+			}
+
+			// Create a test handler that responds with the request path
+			handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				_, _ = w.Write([]byte("OK{" + r.URL.Path + "}"))
+			})
+
+			// Create the server
+			srv, err := cfg.ToServer(
+				context.Background(),
+				host,
+				componenttest.NewNopTelemetrySettings(),
+				handler,
+			)
+			require.NoError(t, err)
+
+			// Create a test request
+			req := httptest.NewRequest(http.MethodGet, "/", nil)
+
+			// Create a response recorder
+			rec := httptest.NewRecorder()
+
+			// Serve the request
+			srv.Handler.ServeHTTP(rec, req)
+
+			// Get the response
+			resp := rec.Result()
+			defer resp.Body.Close()
+
+			// Check the response
+			body, err := io.ReadAll(resp.Body)
+			require.NoError(t, err)
+
+			assert.Equal(t, tc.expectedOutput, string(body))
+		})
+	}
+}
diff --git a/config/confighttp/xconfighttp/go.mod b/config/confighttp/xconfighttp/go.mod
index 53545c9d538..12da6a07518 100644
--- a/config/confighttp/xconfighttp/go.mod
+++ b/config/confighttp/xconfighttp/go.mod
@@ -30,9 +30,11 @@ require (
 	go.opentelemetry.io/collector/component v1.30.0 // indirect
 	go.opentelemetry.io/collector/config/configauth v0.124.0 // indirect
 	go.opentelemetry.io/collector/config/configcompression v1.30.0 // indirect
+	go.opentelemetry.io/collector/config/configmiddleware v0.0.0-00010101000000-000000000000 // indirect
 	go.opentelemetry.io/collector/config/configopaque v1.30.0 // indirect
 	go.opentelemetry.io/collector/config/configtls v1.30.0 // indirect
 	go.opentelemetry.io/collector/extension/extensionauth v1.30.0 // indirect
+	go.opentelemetry.io/collector/extension/extensionmiddleware v0.0.0-00010101000000-000000000000 // indirect
 	go.opentelemetry.io/collector/featuregate v1.30.0 // indirect
 	go.opentelemetry.io/collector/internal/telemetry v0.124.0 // indirect
 	go.opentelemetry.io/collector/pdata v1.30.0 // indirect
@@ -83,3 +85,7 @@ replace go.opentelemetry.io/collector/pipeline => ../../../pipeline
 replace go.opentelemetry.io/collector/internal/telemetry => ../../../internal/telemetry
 
 replace go.opentelemetry.io/collector/featuregate => ../../../featuregate
+
+replace go.opentelemetry.io/collector/extension/extensionmiddleware => ../../../extension/extensionmiddleware
+
+replace go.opentelemetry.io/collector/config/configmiddleware => ../../configmiddleware

From fd6c3735f95ca6c5b7bb15941eafa09370698f4d Mon Sep 17 00:00:00 2001
From: Joshua MacDonald <josh.macdonald@gmail.com>
Date: Mon, 14 Apr 2025 18:03:12 -0700
Subject: [PATCH 02/13] typo

---
 .chloggen/middleware-http.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.chloggen/middleware-http.yaml b/.chloggen/middleware-http.yaml
index a16d7b41323..1ba58fa04a0 100644
--- a/.chloggen/middleware-http.yaml
+++ b/.chloggen/middleware-http.yaml
@@ -4,7 +4,7 @@
 change_type: enhancement
 
 # The name of the component, or a single word describing the area of concern, (e.g. otlpreceiver)
-component: configmiddleware
+component: confighttp
 
 # A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
 note: Add HTTP middleware support.

From d3a42810fd02757716cb45ca7b06d061f4f1c5e7 Mon Sep 17 00:00:00 2001
From: Joshua MacDonald <josh.macdonald@gmail.com>
Date: Fri, 18 Apr 2025 09:33:22 -0700
Subject: [PATCH 03/13] tidy up the tests

---
 cmd/otelcorecol/go.mod                        |  8 ++
 config/confighttp/client_middleware_test.go   | 92 ++++++++-----------
 config/confighttp/confighttp.go               |  4 +-
 config/confighttp/go.mod                      |  5 +-
 config/confighttp/server_middleware_test.go   | 55 +++++------
 config/confighttp/xconfighttp/go.mod          |  4 +-
 exporter/otlphttpexporter/go.mod              |  8 ++
 extension/extensionmiddleware/client_test.go  | 23 -----
 .../extensionmiddlewaretest/nop.go            |  9 ++
 extension/zpagesextension/go.mod              |  8 ++
 internal/e2e/go.mod                           |  8 ++
 otelcol/go.mod                                |  7 ++
 otelcol/otelcoltest/go.mod                    |  7 ++
 receiver/otlpreceiver/go.mod                  |  8 ++
 service/go.mod                                |  8 ++
 service/hostcapabilities/go.mod               |  6 ++
 16 files changed, 147 insertions(+), 113 deletions(-)

diff --git a/cmd/otelcorecol/go.mod b/cmd/otelcorecol/go.mod
index 05db670b0aa..444289030e8 100644
--- a/cmd/otelcorecol/go.mod
+++ b/cmd/otelcorecol/go.mod
@@ -89,6 +89,7 @@ require (
 	go.opentelemetry.io/collector/config/configcompression v1.30.0 // indirect
 	go.opentelemetry.io/collector/config/configgrpc v0.124.0 // indirect
 	go.opentelemetry.io/collector/config/confighttp v0.124.0 // indirect
+	go.opentelemetry.io/collector/config/configmiddleware v0.0.0-00010101000000-000000000000 // indirect
 	go.opentelemetry.io/collector/config/confignet v1.30.0 // indirect
 	go.opentelemetry.io/collector/config/configopaque v1.30.0 // indirect
 	go.opentelemetry.io/collector/config/configretry v1.30.0 // indirect
@@ -107,6 +108,7 @@ require (
 	go.opentelemetry.io/collector/exporter/xexporter v0.124.0 // indirect
 	go.opentelemetry.io/collector/extension/extensionauth v1.30.0 // indirect
 	go.opentelemetry.io/collector/extension/extensioncapabilities v0.124.0 // indirect
+	go.opentelemetry.io/collector/extension/extensionmiddleware v1.30.0 // indirect
 	go.opentelemetry.io/collector/extension/extensiontest v0.124.0 // indirect
 	go.opentelemetry.io/collector/extension/xextension v0.124.0 // indirect
 	go.opentelemetry.io/collector/featuregate v1.30.0 // indirect
@@ -313,3 +315,9 @@ replace go.opentelemetry.io/collector/semconv => ../../semconv
 replace go.opentelemetry.io/collector/service => ../../service
 
 replace go.opentelemetry.io/collector/service/hostcapabilities => ../../service/hostcapabilities
+
+replace go.opentelemetry.io/collector/extension/extensionmiddleware => ../../extension/extensionmiddleware
+
+replace go.opentelemetry.io/collector/config/configmiddleware => ../../config/configmiddleware
+
+replace go.opentelemetry.io/collector/extension/extensionmiddleware/extensionmiddlewaretest => ../../extension/extensionmiddleware/extensionmiddlewaretest
diff --git a/config/confighttp/client_middleware_test.go b/config/confighttp/client_middleware_test.go
index a5424897d7e..6e4f315fc4c 100644
--- a/config/confighttp/client_middleware_test.go
+++ b/config/confighttp/client_middleware_test.go
@@ -17,71 +17,51 @@ import (
 	"go.opentelemetry.io/collector/component"
 	"go.opentelemetry.io/collector/component/componenttest"
 	"go.opentelemetry.io/collector/config/configmiddleware"
+	"go.opentelemetry.io/collector/extension"
 	"go.opentelemetry.io/collector/extension/extensionmiddleware"
+	"go.opentelemetry.io/collector/extension/extensionmiddleware/extensionmiddlewaretest"
 )
 
 // testClientMiddleware is a test middleware that appends a string to the response body
 type testClientMiddleware struct {
-	name string
-}
-
-func (*testClientMiddleware) Start(_ context.Context, _ component.Host) error {
-	return nil
-}
-
-func (*testClientMiddleware) Shutdown(_ context.Context) error {
-	return nil
-}
-
-var _ extensionmiddleware.HTTPClient = &testClientMiddleware{}
-
-// GetHTTPRoundTripper creates a round tripper that appends text to the response body
-func (m *testClientMiddleware) GetHTTPRoundTripper(transport http.RoundTripper) (http.RoundTripper, error) {
-	return &bodyAppenderRoundTripper{
-		name:      m.name,
-		transport: transport,
-	}, nil
-}
-
-// bodyAppenderRoundTripper is a round tripper that appends text to the response body
-type bodyAppenderRoundTripper struct {
-	name      string
-	transport http.RoundTripper
-}
-
-// RoundTrip appends text to the response body
-func (rt *bodyAppenderRoundTripper) RoundTrip(req *http.Request) (*http.Response, error) {
-	resp, err := rt.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 " + rt.name
-
-	// Replace the response body
-	resp.Body = io.NopCloser(strings.NewReader(newBody))
-	resp.ContentLength = int64(len(newBody))
-
-	return resp, nil
+	extension.Extension
+	extensionmiddleware.GetHTTPRoundTripperFunc
 }
 
 func newTestClientMiddleware(name string) component.Component {
 	return &testClientMiddleware{
-		name: name,
+		Extension: extensionmiddlewaretest.NewNop(),
+		GetHTTPRoundTripperFunc: func(transport http.RoundTripper) (http.RoundTripper, error) {
+			return extensionmiddlewaretest.HTTPClientFunc(
+				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
+		},
 	}
 }
 
-func newTestClientConfig(name string) configmiddleware.Middleware {
-	return configmiddleware.Middleware{
-		MiddlewareID: component.MustNewID(name),
+func newTestClientConfig(name string) configmiddleware.Config {
+	return configmiddleware.Config{
+		ID: component.MustNewID(name),
 	}
 }
 
@@ -104,7 +84,7 @@ func TestClientMiddlewares(t *testing.T) {
 	// Test with different middleware configurations
 	testCases := []struct {
 		name           string
-		middlewares    []configmiddleware.Middleware
+		middlewares    []configmiddleware.Config
 		expectedOutput string
 	}{
 		{
@@ -114,14 +94,14 @@ func TestClientMiddlewares(t *testing.T) {
 		},
 		{
 			name: "single_middleware",
-			middlewares: []configmiddleware.Middleware{
+			middlewares: []configmiddleware.Config{
 				newTestClientConfig("test1"),
 			},
 			expectedOutput: "OK\r\noutput by test1",
 		},
 		{
 			name: "multiple_middlewares",
-			middlewares: []configmiddleware.Middleware{
+			middlewares: []configmiddleware.Config{
 				newTestClientConfig("test1"),
 				newTestClientConfig("test2"),
 			},
diff --git a/config/confighttp/confighttp.go b/config/confighttp/confighttp.go
index 96faedf65d2..360d4c773fc 100644
--- a/config/confighttp/confighttp.go
+++ b/config/confighttp/confighttp.go
@@ -116,7 +116,7 @@ type ClientConfig struct {
 	// Middlewares are used to add custom functionality to the HTTP client.
 	// Middleware handlers are applied in the order they appear in this list,
 	// with the first middleware becoming the outermost handler.
-	Middlewares []configmiddleware.Middleware `mapstructure:"middleware,omitempty"`
+	Middlewares []configmiddleware.Config `mapstructure:"middleware,omitempty"`
 }
 
 // CookiesConfig defines the configuration of the HTTP client regarding cookies served by the server.
@@ -365,7 +365,7 @@ type ServerConfig struct {
 	// Middlewares are used to add custom functionality to the HTTP server.
 	// Middleware handlers are applied in the order they appear in this list,
 	// with the first middleware becoming the outermost handler.
-	Middlewares []configmiddleware.Middleware `mapstructure:"middleware,omitempty"`
+	Middlewares []configmiddleware.Config `mapstructure:"middleware,omitempty"`
 }
 
 // NewDefaultServerConfig returns ServerConfig type object with default values.
diff --git a/config/confighttp/go.mod b/config/confighttp/go.mod
index c9f28edf027..1c738c63353 100644
--- a/config/confighttp/go.mod
+++ b/config/confighttp/go.mod
@@ -19,7 +19,8 @@ require (
 	go.opentelemetry.io/collector/extension v1.30.0
 	go.opentelemetry.io/collector/extension/extensionauth v1.30.0
 	go.opentelemetry.io/collector/extension/extensionauth/extensionauthtest v0.124.0
-	go.opentelemetry.io/collector/extension/extensionmiddleware v0.0.0-00010101000000-000000000000
+	go.opentelemetry.io/collector/extension/extensionmiddleware v1.30.0
+	go.opentelemetry.io/collector/extension/extensionmiddleware/extensionmiddlewaretest v0.0.0-00010101000000-000000000000
 	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.60.0
 	go.opentelemetry.io/otel v1.35.0
 	go.uber.org/goleak v1.3.0
@@ -89,3 +90,5 @@ replace go.opentelemetry.io/collector/internal/telemetry => ../../internal/telem
 replace go.opentelemetry.io/collector/pipeline => ../../pipeline
 
 replace go.opentelemetry.io/collector/featuregate => ../../featuregate
+
+replace go.opentelemetry.io/collector/extension/extensionmiddleware/extensionmiddlewaretest => ../../extension/extensionmiddleware/extensionmiddlewaretest
diff --git a/config/confighttp/server_middleware_test.go b/config/confighttp/server_middleware_test.go
index bc9c2ebec7a..e87506d5e55 100644
--- a/config/confighttp/server_middleware_test.go
+++ b/config/confighttp/server_middleware_test.go
@@ -16,43 +16,38 @@ import (
 	"go.opentelemetry.io/collector/component"
 	"go.opentelemetry.io/collector/component/componenttest"
 	"go.opentelemetry.io/collector/config/configmiddleware"
+	"go.opentelemetry.io/collector/extension"
+	"go.opentelemetry.io/collector/extension/extensionmiddleware"
+	"go.opentelemetry.io/collector/extension/extensionmiddleware/extensionmiddlewaretest"
 )
 
-// testServerMiddleware is a test implementation of configmiddleware.Middleware
+// testServerMiddleware is a test implementation of configmiddleware.Config
 type testServerMiddleware struct {
-	name string
-}
-
-func (*testServerMiddleware) Start(_ context.Context, _ component.Host) error {
-	return nil
-}
-
-func (*testServerMiddleware) Shutdown(_ context.Context) error {
-	return nil
-}
-
-func (tm *testServerMiddleware) GetHTTPHandler(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 += tm.name + "/"
-
-		// Call the next handler in the chain
-		handler.ServeHTTP(w, r)
-
-		// Add middleware name to the response
-		_, _ = w.Write([]byte("\r\nserved by " + tm.name))
-	}), nil
+	extension.Extension
+	extensionmiddleware.GetHTTPHandlerFunc
 }
 
 func newTestServerMiddleware(name string) component.Component {
 	return &testServerMiddleware{
-		name: name,
+		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 + "/"
+
+				// 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
+		},
 	}
 }
 
-func newTestServerConfig(name string) configmiddleware.Middleware {
-	return configmiddleware.Middleware{
-		MiddlewareID: component.MustNewID(name),
+func newTestServerConfig(name string) configmiddleware.Config {
+	return configmiddleware.Config{
+		ID: component.MustNewID(name),
 	}
 }
 
@@ -68,7 +63,7 @@ func TestServerMiddleware(t *testing.T) {
 	// Test with different middleware configurations
 	testCases := []struct {
 		name           string
-		middlewares    []configmiddleware.Middleware
+		middlewares    []configmiddleware.Config
 		expectedOutput string
 	}{
 		{
@@ -78,14 +73,14 @@ func TestServerMiddleware(t *testing.T) {
 		},
 		{
 			name: "single_middleware",
-			middlewares: []configmiddleware.Middleware{
+			middlewares: []configmiddleware.Config{
 				newTestServerConfig("test1"),
 			},
 			expectedOutput: "OK{/test1/}\r\nserved by test1",
 		},
 		{
 			name: "multiple_middlewares",
-			middlewares: []configmiddleware.Middleware{
+			middlewares: []configmiddleware.Config{
 				newTestServerConfig("test1"),
 				newTestServerConfig("test2"),
 			},
diff --git a/config/confighttp/xconfighttp/go.mod b/config/confighttp/xconfighttp/go.mod
index 12da6a07518..242306f266d 100644
--- a/config/confighttp/xconfighttp/go.mod
+++ b/config/confighttp/xconfighttp/go.mod
@@ -34,7 +34,7 @@ require (
 	go.opentelemetry.io/collector/config/configopaque v1.30.0 // indirect
 	go.opentelemetry.io/collector/config/configtls v1.30.0 // indirect
 	go.opentelemetry.io/collector/extension/extensionauth v1.30.0 // indirect
-	go.opentelemetry.io/collector/extension/extensionmiddleware v0.0.0-00010101000000-000000000000 // indirect
+	go.opentelemetry.io/collector/extension/extensionmiddleware v1.30.0 // indirect
 	go.opentelemetry.io/collector/featuregate v1.30.0 // indirect
 	go.opentelemetry.io/collector/internal/telemetry v0.124.0 // indirect
 	go.opentelemetry.io/collector/pdata v1.30.0 // indirect
@@ -89,3 +89,5 @@ replace go.opentelemetry.io/collector/featuregate => ../../../featuregate
 replace go.opentelemetry.io/collector/extension/extensionmiddleware => ../../../extension/extensionmiddleware
 
 replace go.opentelemetry.io/collector/config/configmiddleware => ../../configmiddleware
+
+replace go.opentelemetry.io/collector/extension/extensionmiddleware/extensionmiddlewaretest => ../../../extension/extensionmiddleware/extensionmiddlewaretest
diff --git a/exporter/otlphttpexporter/go.mod b/exporter/otlphttpexporter/go.mod
index 779acf340a0..8a6fff2129f 100644
--- a/exporter/otlphttpexporter/go.mod
+++ b/exporter/otlphttpexporter/go.mod
@@ -56,11 +56,13 @@ require (
 	go.opentelemetry.io/auto/sdk v1.1.0 // indirect
 	go.opentelemetry.io/collector/client v1.30.0 // indirect
 	go.opentelemetry.io/collector/config/configauth v0.124.0 // indirect
+	go.opentelemetry.io/collector/config/configmiddleware v0.0.0-00010101000000-000000000000 // indirect
 	go.opentelemetry.io/collector/consumer/consumererror/xconsumererror v0.124.0 // indirect
 	go.opentelemetry.io/collector/consumer/consumertest v0.124.0 // indirect
 	go.opentelemetry.io/collector/consumer/xconsumer v0.124.0 // indirect
 	go.opentelemetry.io/collector/extension v1.30.0 // indirect
 	go.opentelemetry.io/collector/extension/extensionauth v1.30.0 // indirect
+	go.opentelemetry.io/collector/extension/extensionmiddleware v1.30.0 // indirect
 	go.opentelemetry.io/collector/extension/xextension v0.124.0 // indirect
 	go.opentelemetry.io/collector/featuregate v1.30.0 // indirect
 	go.opentelemetry.io/collector/internal/telemetry v0.124.0 // indirect
@@ -161,3 +163,9 @@ replace go.opentelemetry.io/collector/featuregate => ../../featuregate
 replace go.opentelemetry.io/collector/extension/xextension => ../../extension/xextension
 
 replace go.opentelemetry.io/collector/internal/telemetry => ../../internal/telemetry
+
+replace go.opentelemetry.io/collector/config/configmiddleware => ../../config/configmiddleware
+
+replace go.opentelemetry.io/collector/extension/extensionmiddleware => ../../extension/extensionmiddleware
+
+replace go.opentelemetry.io/collector/extension/extensionmiddleware/extensionmiddlewaretest => ../../extension/extensionmiddleware/extensionmiddlewaretest
diff --git a/extension/extensionmiddleware/client_test.go b/extension/extensionmiddleware/client_test.go
index c525ffa3b76..8d4eadcade2 100644
--- a/extension/extensionmiddleware/client_test.go
+++ b/extension/extensionmiddleware/client_test.go
@@ -32,19 +32,6 @@ func TestGetHTTPRoundTripperFunc(t *testing.T) {
 		require.Equal(t, baseRT, rt)
 	})
 
-	t.Run("wrapping function", func(t *testing.T) {
-		// Create a custom round tripper wrapper for testing
-		customRT := &testRoundTripper{base: baseRT}
-
-		wrapperFunc := GetHTTPRoundTripperFunc(func(base http.RoundTripper) (http.RoundTripper, error) {
-			return &testRoundTripper{base: base}, nil
-		})
-
-		rt, err := wrapperFunc.GetHTTPRoundTripper(baseRT)
-		require.NoError(t, err)
-		require.IsType(t, customRT, rt, "wrapper function should return the custom round tripper")
-	})
-
 	t.Run("error function", func(t *testing.T) {
 		expectedErr := errors.New("round tripper error")
 		errorFunc := GetHTTPRoundTripperFunc(func(_ http.RoundTripper) (http.RoundTripper, error) {
@@ -58,16 +45,6 @@ func TestGetHTTPRoundTripperFunc(t *testing.T) {
 	})
 }
 
-// testRoundTripper is a simple round tripper implementation for testing
-type testRoundTripper struct {
-	base http.RoundTripper
-}
-
-func (t *testRoundTripper) RoundTrip(req *http.Request) (*http.Response, error) {
-	// Just delegate to the base round tripper
-	return t.base.RoundTrip(req)
-}
-
 func TestGetGRPCClientOptionsFunc(t *testing.T) {
 	t.Run("nil function", func(t *testing.T) {
 		var nilFunc GetGRPCClientOptionsFunc
diff --git a/extension/extensionmiddleware/extensionmiddlewaretest/nop.go b/extension/extensionmiddleware/extensionmiddlewaretest/nop.go
index 7d8415577cf..6a928331582 100644
--- a/extension/extensionmiddleware/extensionmiddlewaretest/nop.go
+++ b/extension/extensionmiddleware/extensionmiddlewaretest/nop.go
@@ -4,6 +4,8 @@
 package extensionmiddlewaretest // import "go.opentelemetry.io/collector/extension/extensionmiddleware/extensionmiddlewaretest"
 
 import (
+	"net/http"
+
 	"go.opentelemetry.io/collector/extension"
 )
 
@@ -14,3 +16,10 @@ import (
 func NewNop() extension.Extension {
 	return &baseExtension{}
 }
+
+// HTTPClientFunc implements an HTTP client middleware function.
+type HTTPClientFunc func(*http.Request) (*http.Response, error)
+
+func (f HTTPClientFunc) RoundTrip(req *http.Request) (*http.Response, error) {
+	return f(req)
+}
diff --git a/extension/zpagesextension/go.mod b/extension/zpagesextension/go.mod
index 9ee9b204157..8858109b5c4 100644
--- a/extension/zpagesextension/go.mod
+++ b/extension/zpagesextension/go.mod
@@ -43,9 +43,11 @@ require (
 	go.opentelemetry.io/auto/sdk v1.1.0 // indirect
 	go.opentelemetry.io/collector/client v1.30.0 // indirect
 	go.opentelemetry.io/collector/config/configcompression v1.30.0 // indirect
+	go.opentelemetry.io/collector/config/configmiddleware v0.0.0-00010101000000-000000000000 // indirect
 	go.opentelemetry.io/collector/config/configopaque v1.30.0 // indirect
 	go.opentelemetry.io/collector/config/configtls v1.30.0 // indirect
 	go.opentelemetry.io/collector/extension/extensionauth v1.30.0 // indirect
+	go.opentelemetry.io/collector/extension/extensionmiddleware v1.30.0 // indirect
 	go.opentelemetry.io/collector/featuregate v1.30.0 // indirect
 	go.opentelemetry.io/collector/internal/telemetry v0.124.0 // indirect
 	go.opentelemetry.io/collector/pdata v1.30.0 // indirect
@@ -111,3 +113,9 @@ replace go.opentelemetry.io/collector/featuregate => ../../featuregate
 replace go.opentelemetry.io/collector/extension/extensionauth/extensionauthtest => ../../extension/extensionauth/extensionauthtest
 
 replace go.opentelemetry.io/collector/internal/telemetry => ../../internal/telemetry
+
+replace go.opentelemetry.io/collector/extension/extensionmiddleware => ../extensionmiddleware
+
+replace go.opentelemetry.io/collector/config/configmiddleware => ../../config/configmiddleware
+
+replace go.opentelemetry.io/collector/extension/extensionmiddleware/extensionmiddlewaretest => ../extensionmiddleware/extensionmiddlewaretest
diff --git a/internal/e2e/go.mod b/internal/e2e/go.mod
index a2aa3087a0d..006d2ff67b9 100644
--- a/internal/e2e/go.mod
+++ b/internal/e2e/go.mod
@@ -83,6 +83,7 @@ require (
 	go.opentelemetry.io/auto/sdk v1.1.0 // indirect
 	go.opentelemetry.io/collector/client v1.30.0 // indirect
 	go.opentelemetry.io/collector/config/configcompression v1.30.0 // indirect
+	go.opentelemetry.io/collector/config/configmiddleware v0.0.0-00010101000000-000000000000 // indirect
 	go.opentelemetry.io/collector/connector/xconnector v0.124.0 // indirect
 	go.opentelemetry.io/collector/consumer/consumererror v0.124.0 // indirect
 	go.opentelemetry.io/collector/consumer/consumererror/xconsumererror v0.124.0 // indirect
@@ -91,6 +92,7 @@ require (
 	go.opentelemetry.io/collector/exporter/xexporter v0.124.0 // indirect
 	go.opentelemetry.io/collector/extension/extensionauth v1.30.0 // indirect
 	go.opentelemetry.io/collector/extension/extensioncapabilities v0.124.0 // indirect
+	go.opentelemetry.io/collector/extension/extensionmiddleware v1.30.0 // indirect
 	go.opentelemetry.io/collector/extension/extensiontest v0.124.0 // indirect
 	go.opentelemetry.io/collector/extension/xextension v0.124.0 // indirect
 	go.opentelemetry.io/collector/featuregate v1.30.0 // indirect
@@ -261,3 +263,9 @@ replace go.opentelemetry.io/collector/confmap/provider/yamlprovider => ../../con
 replace go.opentelemetry.io/collector/confmap/provider/fileprovider => ../../confmap/provider/fileprovider
 
 replace go.opentelemetry.io/collector/service/hostcapabilities => ../../service/hostcapabilities
+
+replace go.opentelemetry.io/collector/extension/extensionmiddleware/extensionmiddlewaretest => ../../extension/extensionmiddleware/extensionmiddlewaretest
+
+replace go.opentelemetry.io/collector/extension/extensionmiddleware => ../../extension/extensionmiddleware
+
+replace go.opentelemetry.io/collector/config/configmiddleware => ../../config/configmiddleware
diff --git a/otelcol/go.mod b/otelcol/go.mod
index 1815d666143..7aefd6ad37e 100644
--- a/otelcol/go.mod
+++ b/otelcol/go.mod
@@ -74,6 +74,7 @@ require (
 	github.com/yusufpapurcu/wmi v1.2.4 // indirect
 	go.opentelemetry.io/auto/sdk v1.1.0 // indirect
 	go.opentelemetry.io/collector/component/componenttest v0.124.0 // indirect
+	go.opentelemetry.io/collector/config/configmiddleware v0.0.0-00010101000000-000000000000 // indirect
 	go.opentelemetry.io/collector/connector/xconnector v0.124.0 // indirect
 	go.opentelemetry.io/collector/consumer v1.30.0 // indirect
 	go.opentelemetry.io/collector/consumer/consumererror v0.124.0 // indirect
@@ -220,3 +221,9 @@ replace go.opentelemetry.io/collector/confmap/provider/fileprovider => ../confma
 replace go.opentelemetry.io/collector/confmap/provider/yamlprovider => ../confmap/provider/yamlprovider
 
 replace go.opentelemetry.io/collector/internal/telemetry => ../internal/telemetry
+
+replace go.opentelemetry.io/collector/config/configmiddleware => ../config/configmiddleware
+
+replace go.opentelemetry.io/collector/extension/extensionmiddleware => ../extension/extensionmiddleware
+
+replace go.opentelemetry.io/collector/extension/extensionmiddleware/extensionmiddlewaretest => ../extension/extensionmiddleware/extensionmiddlewaretest
diff --git a/otelcol/otelcoltest/go.mod b/otelcol/otelcoltest/go.mod
index f8a4d687273..b1c5bf071a9 100644
--- a/otelcol/otelcoltest/go.mod
+++ b/otelcol/otelcoltest/go.mod
@@ -74,6 +74,7 @@ require (
 	go.opentelemetry.io/collector/exporter/xexporter v0.124.0 // indirect
 	go.opentelemetry.io/collector/extension v1.30.0 // indirect
 	go.opentelemetry.io/collector/extension/extensioncapabilities v0.124.0 // indirect
+	go.opentelemetry.io/collector/extension/extensionmiddleware v0.0.0-00010101000000-000000000000 // indirect
 	go.opentelemetry.io/collector/featuregate v1.30.0 // indirect
 	go.opentelemetry.io/collector/internal/fanoutconsumer v0.124.0 // indirect
 	go.opentelemetry.io/collector/internal/telemetry v0.124.0 // indirect
@@ -229,3 +230,9 @@ replace go.opentelemetry.io/collector/processor/processortest => ../../processor
 replace go.opentelemetry.io/collector/pdata/testdata => ../../pdata/testdata
 
 replace go.opentelemetry.io/collector/internal/telemetry => ../../internal/telemetry
+
+replace go.opentelemetry.io/collector/config/configmiddleware => ../../config/configmiddleware
+
+replace go.opentelemetry.io/collector/extension/extensionmiddleware/extensionmiddlewaretest => ../../extension/extensionmiddleware/extensionmiddlewaretest
+
+replace go.opentelemetry.io/collector/extension/extensionmiddleware => ../../extension/extensionmiddleware
diff --git a/receiver/otlpreceiver/go.mod b/receiver/otlpreceiver/go.mod
index 1cb923fe48e..f4538d79c44 100644
--- a/receiver/otlpreceiver/go.mod
+++ b/receiver/otlpreceiver/go.mod
@@ -65,7 +65,9 @@ require (
 	go.opentelemetry.io/auto/sdk v1.1.0 // indirect
 	go.opentelemetry.io/collector/client v1.30.0 // indirect
 	go.opentelemetry.io/collector/config/configcompression v1.30.0 // indirect
+	go.opentelemetry.io/collector/config/configmiddleware v0.0.0-00010101000000-000000000000 // indirect
 	go.opentelemetry.io/collector/extension/extensionauth v1.30.0 // indirect
+	go.opentelemetry.io/collector/extension/extensionmiddleware v1.30.0 // indirect
 	go.opentelemetry.io/collector/featuregate v1.30.0 // indirect
 	go.opentelemetry.io/collector/pipeline v0.124.0 // indirect
 	go.opentelemetry.io/contrib/bridges/otelzap v0.10.0 // indirect
@@ -151,3 +153,9 @@ retract (
 replace go.opentelemetry.io/collector/featuregate => ../../featuregate
 
 replace go.opentelemetry.io/collector/extension/extensionauth/extensionauthtest => ../../extension/extensionauth/extensionauthtest
+
+replace go.opentelemetry.io/collector/extension/extensionmiddleware => ../../extension/extensionmiddleware
+
+replace go.opentelemetry.io/collector/config/configmiddleware => ../../config/configmiddleware
+
+replace go.opentelemetry.io/collector/extension/extensionmiddleware/extensionmiddlewaretest => ../../extension/extensionmiddleware/extensionmiddlewaretest
diff --git a/service/go.mod b/service/go.mod
index 6ab66b2ee64..65549bc6f3d 100644
--- a/service/go.mod
+++ b/service/go.mod
@@ -103,10 +103,12 @@ require (
 	go.opentelemetry.io/collector/client v1.30.0 // indirect
 	go.opentelemetry.io/collector/config/configauth v0.124.0 // indirect
 	go.opentelemetry.io/collector/config/configcompression v1.30.0 // indirect
+	go.opentelemetry.io/collector/config/configmiddleware v0.0.0-00010101000000-000000000000 // indirect
 	go.opentelemetry.io/collector/config/configopaque v1.30.0 // indirect
 	go.opentelemetry.io/collector/config/configtls v1.30.0 // indirect
 	go.opentelemetry.io/collector/consumer/consumererror v0.124.0 // indirect
 	go.opentelemetry.io/collector/extension/extensionauth v1.30.0 // indirect
+	go.opentelemetry.io/collector/extension/extensionmiddleware v1.30.0 // indirect
 	go.opentelemetry.io/contrib/bridges/otelzap v0.10.0 // indirect
 	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.60.0 // indirect
 	go.opentelemetry.io/contrib/zpages v0.60.0 // indirect
@@ -234,3 +236,9 @@ replace go.opentelemetry.io/collector/otelcol => ../otelcol
 replace go.opentelemetry.io/collector/confmap/provider/yamlprovider => ../confmap/provider/yamlprovider
 
 replace go.opentelemetry.io/collector/confmap/provider/fileprovider => ../confmap/provider/fileprovider
+
+replace go.opentelemetry.io/collector/extension/extensionmiddleware => ../extension/extensionmiddleware
+
+replace go.opentelemetry.io/collector/config/configmiddleware => ../config/configmiddleware
+
+replace go.opentelemetry.io/collector/extension/extensionmiddleware/extensionmiddlewaretest => ../extension/extensionmiddleware/extensionmiddlewaretest
diff --git a/service/hostcapabilities/go.mod b/service/hostcapabilities/go.mod
index 02833db0656..9e33baab67e 100644
--- a/service/hostcapabilities/go.mod
+++ b/service/hostcapabilities/go.mod
@@ -89,3 +89,9 @@ replace go.opentelemetry.io/collector/otelcol => ../../otelcol
 replace go.opentelemetry.io/collector/confmap/provider/fileprovider => ../../confmap/provider/fileprovider
 
 replace go.opentelemetry.io/collector/confmap/provider/yamlprovider => ../../confmap/provider/yamlprovider
+
+replace go.opentelemetry.io/collector/extension/extensionmiddleware/extensionmiddlewaretest => ../../extension/extensionmiddleware/extensionmiddlewaretest
+
+replace go.opentelemetry.io/collector/config/configmiddleware => ../../config/configmiddleware
+
+replace go.opentelemetry.io/collector/extension/extensionmiddleware => ../../extension/extensionmiddleware

From 5fad04b7db6548694c124108570805be2deffb36 Mon Sep 17 00:00:00 2001
From: Joshua MacDonald <josh.macdonald@gmail.com>
Date: Fri, 18 Apr 2025 09:38:34 -0700
Subject: [PATCH 04/13] small test

---
 .../extensionmiddlewaretest/nop_test.go          | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/extension/extensionmiddleware/extensionmiddlewaretest/nop_test.go b/extension/extensionmiddleware/extensionmiddlewaretest/nop_test.go
index 4b136369f75..bebd0355a9a 100644
--- a/extension/extensionmiddleware/extensionmiddlewaretest/nop_test.go
+++ b/extension/extensionmiddleware/extensionmiddlewaretest/nop_test.go
@@ -4,6 +4,7 @@
 package extensionmiddlewaretest
 
 import (
+	"net/http"
 	"testing"
 
 	"github.com/stretchr/testify/require"
@@ -42,3 +43,18 @@ func TestNopServer(t *testing.T) {
 	require.NoError(t, err)
 	require.Nil(t, grpcOpts)
 }
+
+func TestHTTPClientFunc(t *testing.T) {
+	called := false
+	req := &http.Request{}
+	resp := &http.Response{}
+
+	f := HTTPClientFunc(func(r *http.Request) (*http.Response, error) {
+		called = true
+		return resp, nil
+	})
+
+	result, _ := f.RoundTrip(req)
+	require.True(t, called)
+	require.Equal(t, resp, result)
+}

From 16a4d92afa719a859763ffda29977028e6077404 Mon Sep 17 00:00:00 2001
From: Joshua MacDonald <josh.macdonald@gmail.com>
Date: Fri, 18 Apr 2025 10:08:56 -0700
Subject: [PATCH 05/13] update builder-config.yaml

---
 cmd/otelcorecol/builder-config.yaml                |  3 +++
 cmd/otelcorecol/go.mod                             | 14 +++++++-------
 .../extensionmiddlewaretest/nop_test.go            |  1 +
 otelcol/go.mod                                     |  1 -
 otelcol/otelcoltest/go.mod                         |  1 -
 5 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/cmd/otelcorecol/builder-config.yaml b/cmd/otelcorecol/builder-config.yaml
index 47585926e72..a0dd3029a1f 100644
--- a/cmd/otelcorecol/builder-config.yaml
+++ b/cmd/otelcorecol/builder-config.yaml
@@ -46,6 +46,7 @@ replaces:
   - go.opentelemetry.io/collector/config/configcompression => ../../config/configcompression
   - go.opentelemetry.io/collector/config/configgrpc => ../../config/configgrpc
   - go.opentelemetry.io/collector/config/confighttp => ../../config/confighttp
+  - go.opentelemetry.io/collector/config/configmiddleware => ../../config/configmiddleware
   - go.opentelemetry.io/collector/config/confignet => ../../config/confignet
   - go.opentelemetry.io/collector/config/configopaque => ../../config/configopaque
   - go.opentelemetry.io/collector/config/configretry => ../../config/configretry
@@ -79,6 +80,8 @@ replaces:
   - go.opentelemetry.io/collector/extension/extensionauth => ../../extension/extensionauth
   - go.opentelemetry.io/collector/extension/extensionauth/extensionauthtest => ../../extension/extensionauth/extensionauthtest
   - go.opentelemetry.io/collector/extension/extensioncapabilities => ../../extension/extensioncapabilities
+  - go.opentelemetry.io/collector/extension/extensionmiddleware => ../../extension/extensionmiddleware
+  - go.opentelemetry.io/collector/extension/extensionmiddleware/extensionmiddlewaretest => ../../extension/extensionmiddleware/extensionmiddlewaretest
   - go.opentelemetry.io/collector/extension/extensiontest => ../../extension/extensiontest
   - go.opentelemetry.io/collector/extension/memorylimiterextension => ../../extension/memorylimiterextension
   - go.opentelemetry.io/collector/extension/xextension => ../../extension/xextension
diff --git a/cmd/otelcorecol/go.mod b/cmd/otelcorecol/go.mod
index 444289030e8..bd98ec7fea2 100644
--- a/cmd/otelcorecol/go.mod
+++ b/cmd/otelcorecol/go.mod
@@ -4,7 +4,7 @@ module go.opentelemetry.io/collector/cmd/otelcorecol
 
 go 1.23.0
 
-toolchain go1.23.8
+toolchain go1.24.1
 
 require (
 	go.opentelemetry.io/collector/component v1.30.0
@@ -188,6 +188,8 @@ replace go.opentelemetry.io/collector/config/configgrpc => ../../config/configgr
 
 replace go.opentelemetry.io/collector/config/confighttp => ../../config/confighttp
 
+replace go.opentelemetry.io/collector/config/configmiddleware => ../../config/configmiddleware
+
 replace go.opentelemetry.io/collector/config/confignet => ../../config/confignet
 
 replace go.opentelemetry.io/collector/config/configopaque => ../../config/configopaque
@@ -254,6 +256,10 @@ replace go.opentelemetry.io/collector/extension/extensionauth/extensionauthtest
 
 replace go.opentelemetry.io/collector/extension/extensioncapabilities => ../../extension/extensioncapabilities
 
+replace go.opentelemetry.io/collector/extension/extensionmiddleware => ../../extension/extensionmiddleware
+
+replace go.opentelemetry.io/collector/extension/extensionmiddleware/extensionmiddlewaretest => ../../extension/extensionmiddleware/extensionmiddlewaretest
+
 replace go.opentelemetry.io/collector/extension/extensiontest => ../../extension/extensiontest
 
 replace go.opentelemetry.io/collector/extension/memorylimiterextension => ../../extension/memorylimiterextension
@@ -315,9 +321,3 @@ replace go.opentelemetry.io/collector/semconv => ../../semconv
 replace go.opentelemetry.io/collector/service => ../../service
 
 replace go.opentelemetry.io/collector/service/hostcapabilities => ../../service/hostcapabilities
-
-replace go.opentelemetry.io/collector/extension/extensionmiddleware => ../../extension/extensionmiddleware
-
-replace go.opentelemetry.io/collector/config/configmiddleware => ../../config/configmiddleware
-
-replace go.opentelemetry.io/collector/extension/extensionmiddleware/extensionmiddlewaretest => ../../extension/extensionmiddleware/extensionmiddlewaretest
diff --git a/extension/extensionmiddleware/extensionmiddlewaretest/nop_test.go b/extension/extensionmiddleware/extensionmiddlewaretest/nop_test.go
index bebd0355a9a..fe5d12408d8 100644
--- a/extension/extensionmiddleware/extensionmiddlewaretest/nop_test.go
+++ b/extension/extensionmiddleware/extensionmiddlewaretest/nop_test.go
@@ -50,6 +50,7 @@ func TestHTTPClientFunc(t *testing.T) {
 	resp := &http.Response{}
 
 	f := HTTPClientFunc(func(r *http.Request) (*http.Response, error) {
+		require.Equal(t, r, resp)
 		called = true
 		return resp, nil
 	})
diff --git a/otelcol/go.mod b/otelcol/go.mod
index 7aefd6ad37e..d3aafc87a7d 100644
--- a/otelcol/go.mod
+++ b/otelcol/go.mod
@@ -74,7 +74,6 @@ require (
 	github.com/yusufpapurcu/wmi v1.2.4 // indirect
 	go.opentelemetry.io/auto/sdk v1.1.0 // indirect
 	go.opentelemetry.io/collector/component/componenttest v0.124.0 // indirect
-	go.opentelemetry.io/collector/config/configmiddleware v0.0.0-00010101000000-000000000000 // indirect
 	go.opentelemetry.io/collector/connector/xconnector v0.124.0 // indirect
 	go.opentelemetry.io/collector/consumer v1.30.0 // indirect
 	go.opentelemetry.io/collector/consumer/consumererror v0.124.0 // indirect
diff --git a/otelcol/otelcoltest/go.mod b/otelcol/otelcoltest/go.mod
index b1c5bf071a9..24c4b1ab08f 100644
--- a/otelcol/otelcoltest/go.mod
+++ b/otelcol/otelcoltest/go.mod
@@ -74,7 +74,6 @@ require (
 	go.opentelemetry.io/collector/exporter/xexporter v0.124.0 // indirect
 	go.opentelemetry.io/collector/extension v1.30.0 // indirect
 	go.opentelemetry.io/collector/extension/extensioncapabilities v0.124.0 // indirect
-	go.opentelemetry.io/collector/extension/extensionmiddleware v0.0.0-00010101000000-000000000000 // indirect
 	go.opentelemetry.io/collector/featuregate v1.30.0 // indirect
 	go.opentelemetry.io/collector/internal/fanoutconsumer v0.124.0 // indirect
 	go.opentelemetry.io/collector/internal/telemetry v0.124.0 // indirect

From a8141565154312e54b48262fddadc6d7cf6d6124 Mon Sep 17 00:00:00 2001
From: Joshua MacDonald <josh.macdonald@gmail.com>
Date: Fri, 18 Apr 2025 10:11:11 -0700
Subject: [PATCH 06/13] more comment nop

---
 extension/extensionmiddleware/extensionmiddlewaretest/nop.go | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/extension/extensionmiddleware/extensionmiddlewaretest/nop.go b/extension/extensionmiddleware/extensionmiddlewaretest/nop.go
index 6a928331582..b15addccf2d 100644
--- a/extension/extensionmiddleware/extensionmiddlewaretest/nop.go
+++ b/extension/extensionmiddleware/extensionmiddlewaretest/nop.go
@@ -17,7 +17,9 @@ func NewNop() extension.Extension {
 	return &baseExtension{}
 }
 
-// HTTPClientFunc implements an HTTP client middleware function.
+// HTTPClientFunc implements an HTTP client middleware function.  This
+// is the equivalent of net/http.HandlerFunc for creating a
+// net/http.RoundTripper from a function.
 type HTTPClientFunc func(*http.Request) (*http.Response, error)
 
 func (f HTTPClientFunc) RoundTrip(req *http.Request) (*http.Response, error) {

From bf02835f5cc9c17902e805de11d756bb8ea8d24c Mon Sep 17 00:00:00 2001
From: Joshua MacDonald <josh.macdonald@gmail.com>
Date: Fri, 18 Apr 2025 10:16:42 -0700
Subject: [PATCH 07/13] lint

---
 .chloggen/middleware-http.yaml | 2 +-
 CHANGELOG.md                   | 2 +-
 docs/rfcs/env-vars.md          | 5 ++---
 3 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/.chloggen/middleware-http.yaml b/.chloggen/middleware-http.yaml
index 1ba58fa04a0..2b916615cd8 100644
--- a/.chloggen/middleware-http.yaml
+++ b/.chloggen/middleware-http.yaml
@@ -10,7 +10,7 @@ component: confighttp
 note: Add HTTP middleware support.
 
 # One or more tracking issues or pull requests related to the change
-issues: [12603, 9591]
+issues: [12603, 9591, 7441]
 
 # (Optional) One or more lines of additional information to render under the primary note.
 # These lines will be padded with 2 spaces and then inserted directly into the document.
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6bbc41e44ba..adfb77288b1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3464,7 +3464,7 @@ This release is marked as "bad" since the metrics pipelines will produce bad dat
 - Rename ForEach (in pdata) with Range to be consistent with sync.Map (#2931)
 - Rename `componenthelper.Start` to `componenthelper.StartFunc` (#2880)
 - Rename `componenthelper.Stop` to `componenthelper.StopFunc` (#2880)
-- Remove `exporterheleper.WithCustomUnmarshaler`, `processorhelper.WithCustomUnmarshaler`, `receiverhelper.WithCustomUnmarshaler`, `extensionheleper.WithCustomUnmarshaler`, implement `config.CustomUnmarshaler` interface instead (#2867)
+- Remove `exporterhelper.WithCustomUnmarshaler`, `processorhelper.WithCustomUnmarshaler`, `receiverhelper.WithCustomUnmarshaler`, `extensionhelper.WithCustomUnmarshaler`, implement `config.CustomUnmarshaler` interface instead (#2867)
 - Remove `component.CustomUnmarshaler` implement `config.CustomUnmarshaler` interface instead (#2867)
 - Remove `testutil.HostPortFromAddr`, users can write their own parsing helper (#2919)
 - Remove `configparser.DecodeTypeAndName`, use `config.IDFromString` (#2869)
diff --git a/docs/rfcs/env-vars.md b/docs/rfcs/env-vars.md
index afff3dd2c00..9c6b6e9224f 100644
--- a/docs/rfcs/env-vars.md
+++ b/docs/rfcs/env-vars.md
@@ -104,9 +104,8 @@ environment variable whose name is stored in the URL
 The environment variable value is parsed by the yaml.v3 parser to an
 any-typed variable. The yaml.v3 parser mostly follows the YAML v1.2
 specification with [*some exceptions*](https://github.com/go-yaml/yaml#compatibility). 
-You can see
-how it works for some edge cases in this example:
-[`go.dev/play/p/3vNLznwSZQe`](https://go.dev/play/p/3vNLznwSZQe).
+You can see how it works for some edge cases in
+[this go.dev/play example](https://go.dev/play/p/3vNLznwSZQe).
 
 ### Issues of current behavior
 

From 981de8b9d2163db91c50677d4699a62d5317659c Mon Sep 17 00:00:00 2001
From: Joshua MacDonald <josh.macdonald@gmail.com>
Date: Fri, 18 Apr 2025 10:26:35 -0700
Subject: [PATCH 08/13] revert toolchain

---
 cmd/otelcorecol/go.mod | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/cmd/otelcorecol/go.mod b/cmd/otelcorecol/go.mod
index bd98ec7fea2..75241b1b7e1 100644
--- a/cmd/otelcorecol/go.mod
+++ b/cmd/otelcorecol/go.mod
@@ -4,7 +4,7 @@ module go.opentelemetry.io/collector/cmd/otelcorecol
 
 go 1.23.0
 
-toolchain go1.24.1
+toolchain go1.23.8
 
 require (
 	go.opentelemetry.io/collector/component v1.30.0

From 17573e2cadbb539c87de0134a5f611ea450e911d Mon Sep 17 00:00:00 2001
From: Joshua MacDonald <josh.macdonald@gmail.com>
Date: Fri, 18 Apr 2025 10:32:13 -0700
Subject: [PATCH 09/13] replaces for builder command

---
 cmd/builder/internal/builder/main_test.go | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/cmd/builder/internal/builder/main_test.go b/cmd/builder/internal/builder/main_test.go
index 0d49d538b6f..0d6cf0d528e 100644
--- a/cmd/builder/internal/builder/main_test.go
+++ b/cmd/builder/internal/builder/main_test.go
@@ -47,6 +47,7 @@ var replaceModules = []string{
 	"/config/configcompression",
 	"/config/configgrpc",
 	"/config/confighttp",
+	"/config/configmiddleware",
 	"/config/confignet",
 	"/config/configopaque",
 	"/config/configretry",
@@ -79,6 +80,8 @@ var replaceModules = []string{
 	"/extension/extensionauth",
 	"/extension/extensionauth/extensionauthtest",
 	"/extension/extensioncapabilities",
+	"/extension/extensionmiddleware",
+	"/extension/extensionmiddleware/extensionmiddlewaretest",
 	"/extension/extensiontest",
 	"/extension/zpagesextension",
 	"/extension/xextension",

From ece76951a7e5ff5abda7fcb986874a36f1a116d1 Mon Sep 17 00:00:00 2001
From: Joshua MacDonald <josh.macdonald@gmail.com>
Date: Fri, 18 Apr 2025 10:40:01 -0700
Subject: [PATCH 10/13] test fix

---
 .../extensionmiddleware/extensionmiddlewaretest/nop_test.go     | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/extension/extensionmiddleware/extensionmiddlewaretest/nop_test.go b/extension/extensionmiddleware/extensionmiddlewaretest/nop_test.go
index fe5d12408d8..8c92eca20fe 100644
--- a/extension/extensionmiddleware/extensionmiddlewaretest/nop_test.go
+++ b/extension/extensionmiddleware/extensionmiddlewaretest/nop_test.go
@@ -50,7 +50,7 @@ func TestHTTPClientFunc(t *testing.T) {
 	resp := &http.Response{}
 
 	f := HTTPClientFunc(func(r *http.Request) (*http.Response, error) {
-		require.Equal(t, r, resp)
+		require.Equal(t, r, req)
 		called = true
 		return resp, nil
 	})

From e88240187ec66ce078841ddd3fac3118765f89af Mon Sep 17 00:00:00 2001
From: Joshua MacDonald <josh.macdonald@gmail.com>
Date: Fri, 18 Apr 2025 10:45:32 -0700
Subject: [PATCH 11/13] comments

---
 config/confighttp/confighttp.go | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/config/confighttp/confighttp.go b/config/confighttp/confighttp.go
index 360d4c773fc..a7c069048d6 100644
--- a/config/confighttp/confighttp.go
+++ b/config/confighttp/confighttp.go
@@ -114,7 +114,7 @@ type ClientConfig struct {
 	Cookies *CookiesConfig `mapstructure:"cookies,omitempty"`
 
 	// Middlewares are used to add custom functionality to the HTTP client.
-	// Middleware handlers are applied in the order they appear in this list,
+	// Middleware handlers are called in the order they appear in this list,
 	// with the first middleware becoming the outermost handler.
 	Middlewares []configmiddleware.Config `mapstructure:"middleware,omitempty"`
 }
@@ -201,8 +201,8 @@ func (hcs *ClientConfig) ToClient(ctx context.Context, host component.Host, sett
 
 	clientTransport := (http.RoundTripper)(transport)
 
-	// Apply middlewares in reverse order so they are applied in
-	// order. The first middleware runs after authentication.
+	// Apply middlewares in reverse order so they execute in
+	// forward order. The first middleware runs after authentication.
 	for i := len(hcs.Middlewares) - 1; i >= 0; i-- {
 		var wrapper func(http.RoundTripper) (http.RoundTripper, error)
 		wrapper, err = hcs.Middlewares[i].GetHTTPClientRoundTripper(ctx, host.GetExtensions())
@@ -363,7 +363,7 @@ type ServerConfig struct {
 	IdleTimeout time.Duration `mapstructure:"idle_timeout"`
 
 	// Middlewares are used to add custom functionality to the HTTP server.
-	// Middleware handlers are applied in the order they appear in this list,
+	// Middleware handlers are called in the order they appear in this list,
 	// with the first middleware becoming the outermost handler.
 	Middlewares []configmiddleware.Config `mapstructure:"middleware,omitempty"`
 }
@@ -453,9 +453,9 @@ func (hss *ServerConfig) ToServer(ctx context.Context, host component.Host, sett
 		hss.CompressionAlgorithms = defaultCompressionAlgorithms
 	}
 
-	// Apply middlewares in reverse order so they are applied in
-	// order.  The first middleware runs after decompression,
-	// below, preceded by Auth, CORS, etc.
+	// Apply middlewares in reverse order so they execute in
+	// forward order.  The first middleware runs after
+	// decompression, below, preceded by Auth, CORS, etc.
 	for i := len(hss.Middlewares) - 1; i >= 0; i-- {
 		wrapper, err := hss.Middlewares[i].GetHTTPServerHandler(ctx, host.GetExtensions())
 		// If we failed to get the middleware

From 472a2e962888765ba52f28ec7ca32fe6a08d3b1a Mon Sep 17 00:00:00 2001
From: Joshua MacDonald <josh.macdonald@gmail.com>
Date: Fri, 18 Apr 2025 11:25:31 -0700
Subject: [PATCH 12/13] improve coverage

---
 config/confighttp/client_middleware_test.go | 116 +++++++++++++++++++
 config/confighttp/server_middleware_test.go | 118 ++++++++++++++++++++
 2 files changed, 234 insertions(+)

diff --git a/config/confighttp/client_middleware_test.go b/config/confighttp/client_middleware_test.go
index 6e4f315fc4c..c9427d9fd02 100644
--- a/config/confighttp/client_middleware_test.go
+++ b/config/confighttp/client_middleware_test.go
@@ -5,6 +5,7 @@ package confighttp
 
 import (
 	"context"
+	"errors"
 	"io"
 	"net/http"
 	"net/http/httptest"
@@ -137,3 +138,118 @@ func TestClientMiddlewares(t *testing.T) {
 		})
 	}
 }
+
+func TestClientMiddlewareErrors(t *testing.T) {
+	// Create a test server that returns "OK"
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		_, _ = w.Write([]byte("OK"))
+	}))
+	defer server.Close()
+
+	// Test cases for HTTP client middleware errors
+	httpTests := []struct {
+		name    string
+		host    component.Host
+		config  ClientConfig
+		errText string
+	}{
+		{
+			name: "extension_not_found",
+			host: &mockHost{
+				ext: map[component.ID]component.Component{},
+			},
+			config: ClientConfig{
+				Endpoint: server.URL,
+				Middlewares: []configmiddleware.Config{
+					{
+						ID: component.MustNewID("nonexistent"),
+					},
+				},
+			},
+			errText: "failed to resolve middleware \"nonexistent\": middleware not found",
+		},
+		{
+			name: "get_round_tripper_fails",
+			host: &mockHost{
+				ext: map[component.ID]component.Component{
+					component.MustNewID("errormw"): extensionmiddlewaretest.NewErr(errors.New("http middleware error")),
+				},
+			},
+			config: ClientConfig{
+				Endpoint: server.URL,
+				Middlewares: []configmiddleware.Config{
+					{
+						ID: component.MustNewID("errormw"),
+					},
+				},
+			},
+			errText: "http middleware error",
+		},
+	}
+
+	for _, tc := range httpTests {
+		t.Run(tc.name, func(t *testing.T) {
+			// Trying to create the client should fail
+			_, err := tc.config.ToClient(context.Background(), tc.host, componenttest.NewNopTelemetrySettings())
+			require.Error(t, err)
+			assert.Contains(t, err.Error(), tc.errText)
+		})
+	}
+}
+
+// Test failures for gRPC client middlewares by creating a mock implementation
+// that can fail in similar ways to HTTP clients
+func TestGRPCClientMiddlewareErrors(t *testing.T) {
+	// Test cases for gRPC client middleware errors
+	grpcTests := []struct {
+		name    string
+		host    component.Host
+		config  ClientConfig
+		errText string
+	}{
+		{
+			name: "grpc_extension_not_found",
+			host: &mockHost{
+				ext: map[component.ID]component.Component{},
+			},
+			config: ClientConfig{
+				Endpoint: "localhost:1234",
+				Middlewares: []configmiddleware.Config{
+					{
+						ID: component.MustNewID("nonexistent"),
+					},
+				},
+			},
+			errText: "failed to resolve middleware \"nonexistent\": middleware not found",
+		},
+		{
+			name: "grpc_get_client_options_fails",
+			host: &mockHost{
+				ext: map[component.ID]component.Component{
+					component.MustNewID("errormw"): extensionmiddlewaretest.NewErr(errors.New("grpc middleware error")),
+				},
+			},
+			config: ClientConfig{
+				Endpoint: "localhost:1234",
+				Middlewares: []configmiddleware.Config{
+					{
+						ID: component.MustNewID("errormw"),
+					},
+				},
+			},
+			errText: "grpc middleware error",
+		},
+	}
+
+	for _, tc := range grpcTests {
+		t.Run(tc.name, func(t *testing.T) {
+			// For gRPC, we need to use the configgrpc.ClientConfig structure
+			// We'll test the middleware failure path here using the HTTP client approach,
+			// as the middleware resolution logic is the same
+			_, err := tc.config.ToClient(context.Background(), tc.host, componenttest.NewNopTelemetrySettings())
+			require.Error(t, err)
+			assert.Contains(t, err.Error(), tc.errText)
+		})
+	}
+}
diff --git a/config/confighttp/server_middleware_test.go b/config/confighttp/server_middleware_test.go
index e87506d5e55..ca383ccfe38 100644
--- a/config/confighttp/server_middleware_test.go
+++ b/config/confighttp/server_middleware_test.go
@@ -5,6 +5,7 @@ package confighttp
 
 import (
 	"context"
+	"errors"
 	"io"
 	"net/http"
 	"net/http/httptest"
@@ -131,3 +132,120 @@ func TestServerMiddleware(t *testing.T) {
 		})
 	}
 }
+
+func TestServerMiddlewareErrors(t *testing.T) {
+	// Create a basic handler for testing
+	handler := http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		_, _ = w.Write([]byte("OK"))
+	})
+
+	// Test cases for HTTP server middleware errors
+	httpTests := []struct {
+		name    string
+		host    component.Host
+		config  ServerConfig
+		errText string
+	}{
+		{
+			name: "extension_not_found",
+			host: &mockHost{
+				ext: map[component.ID]component.Component{},
+			},
+			config: ServerConfig{
+				Endpoint: "localhost:0",
+				Middlewares: []configmiddleware.Config{
+					{
+						ID: component.MustNewID("nonexistent"),
+					},
+				},
+			},
+			errText: "failed to resolve middleware \"nonexistent\": middleware not found",
+		},
+		{
+			name: "get_http_handler_fails",
+			host: &mockHost{
+				ext: map[component.ID]component.Component{
+					component.MustNewID("errormw"): extensionmiddlewaretest.NewErr(errors.New("http middleware error")),
+				},
+			},
+			config: ServerConfig{
+				Endpoint: "localhost:0",
+				Middlewares: []configmiddleware.Config{
+					{
+						ID: component.MustNewID("errormw"),
+					},
+				},
+			},
+			errText: "http middleware error",
+		},
+	}
+
+	for _, tc := range httpTests {
+		t.Run(tc.name, func(t *testing.T) {
+			// Trying to create the server should fail
+			_, err := tc.config.ToServer(
+				context.Background(),
+				tc.host,
+				componenttest.NewNopTelemetrySettings(),
+				handler,
+			)
+			require.Error(t, err)
+			assert.Contains(t, err.Error(), tc.errText)
+		})
+	}
+
+	// Test cases for gRPC server middleware errors
+	grpcTests := []struct {
+		name    string
+		host    component.Host
+		config  ServerConfig
+		errText string
+	}{
+		{
+			name: "grpc_extension_not_found",
+			host: &mockHost{
+				ext: map[component.ID]component.Component{},
+			},
+			config: ServerConfig{
+				Endpoint: "localhost:0",
+				Middlewares: []configmiddleware.Config{
+					{
+						ID: component.MustNewID("nonexistent"),
+					},
+				},
+			},
+			errText: "failed to resolve middleware \"nonexistent\": middleware not found",
+		},
+		{
+			name: "get_grpc_handler_fails",
+			host: &mockHost{
+				ext: map[component.ID]component.Component{
+					component.MustNewID("errormw"): extensionmiddlewaretest.NewErr(errors.New("grpc middleware error")),
+				},
+			},
+			config: ServerConfig{
+				Endpoint: "localhost:0",
+				Middlewares: []configmiddleware.Config{
+					{
+						ID: component.MustNewID("errormw"),
+					},
+				},
+			},
+			errText: "grpc middleware error",
+		},
+	}
+
+	for _, tc := range grpcTests {
+		t.Run(tc.name, func(t *testing.T) {
+			// Trying to create the server should fail
+			_, err := tc.config.ToServer(
+				context.Background(),
+				tc.host,
+				componenttest.NewNopTelemetrySettings(),
+				handler,
+			)
+			require.Error(t, err)
+			assert.Contains(t, err.Error(), tc.errText)
+		})
+	}
+}

From abc302dcd9d39259d0b102991b3644060571b22b Mon Sep 17 00:00:00 2001
From: Joshua MacDonald <josh.macdonald@gmail.com>
Date: Fri, 18 Apr 2025 11:33:21 -0700
Subject: [PATCH 13/13] Revert

---
 CHANGELOG.md          | 2 +-
 docs/rfcs/env-vars.md | 5 +++--
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index adfb77288b1..6bbc41e44ba 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3464,7 +3464,7 @@ This release is marked as "bad" since the metrics pipelines will produce bad dat
 - Rename ForEach (in pdata) with Range to be consistent with sync.Map (#2931)
 - Rename `componenthelper.Start` to `componenthelper.StartFunc` (#2880)
 - Rename `componenthelper.Stop` to `componenthelper.StopFunc` (#2880)
-- Remove `exporterhelper.WithCustomUnmarshaler`, `processorhelper.WithCustomUnmarshaler`, `receiverhelper.WithCustomUnmarshaler`, `extensionhelper.WithCustomUnmarshaler`, implement `config.CustomUnmarshaler` interface instead (#2867)
+- Remove `exporterheleper.WithCustomUnmarshaler`, `processorhelper.WithCustomUnmarshaler`, `receiverhelper.WithCustomUnmarshaler`, `extensionheleper.WithCustomUnmarshaler`, implement `config.CustomUnmarshaler` interface instead (#2867)
 - Remove `component.CustomUnmarshaler` implement `config.CustomUnmarshaler` interface instead (#2867)
 - Remove `testutil.HostPortFromAddr`, users can write their own parsing helper (#2919)
 - Remove `configparser.DecodeTypeAndName`, use `config.IDFromString` (#2869)
diff --git a/docs/rfcs/env-vars.md b/docs/rfcs/env-vars.md
index 9c6b6e9224f..afff3dd2c00 100644
--- a/docs/rfcs/env-vars.md
+++ b/docs/rfcs/env-vars.md
@@ -104,8 +104,9 @@ environment variable whose name is stored in the URL
 The environment variable value is parsed by the yaml.v3 parser to an
 any-typed variable. The yaml.v3 parser mostly follows the YAML v1.2
 specification with [*some exceptions*](https://github.com/go-yaml/yaml#compatibility). 
-You can see how it works for some edge cases in
-[this go.dev/play example](https://go.dev/play/p/3vNLznwSZQe).
+You can see
+how it works for some edge cases in this example:
+[`go.dev/play/p/3vNLznwSZQe`](https://go.dev/play/p/3vNLznwSZQe).
 
 ### Issues of current behavior