[extension/remotetap] add basic implementation of the extension

.chloggen/remotetap_impl.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: new_component
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: remotetapextension
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: First implementation of remotetapextension
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [29726]
+
+# (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:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# 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: []

extension/remotetapextension/config.go

@@ -4,18 +4,34 @@
 package remotetapextension // import "github.com/open-telemetry/opentelemetry-collector-contrib/extension/remotetapextension"
 
 import (
+	"errors"
+
 	"go.opentelemetry.io/collector/component"
 	"go.opentelemetry.io/collector/config/confighttp"
 )
 
+const defaultEndpoint = "127.0.0.1:11000"
+
+type TapInfo struct {
+	Name     string `mapstructure:"name" json:"name"`
+	Endpoint string `mapstructure:"endpoint" json:"endpoint"`
+}
 type Config struct {
 	confighttp.HTTPServerSettings `mapstructure:",squash"` // squash ensures fields are correctly decoded in embedded struct
+	Taps                          []TapInfo                `mapstructure:"taps"`
 }
 
 func createDefaultConfig() component.Config {
 	return &Config{
 		HTTPServerSettings: confighttp.HTTPServerSettings{
-			Endpoint: "127.0.0.1:11000",
+			Endpoint: defaultEndpoint,
 		},
 	}
 }
+
+func (c *Config) Validate() error {
+	if len(c.Taps) == 0 {
+		return errors.New("no taps defined")
+	}
+	return nil
+}

extension/remotetapextension/config_test.go

@@ -0,0 +1,74 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package remotetapextension
+
+import (
+	"errors"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	"go.opentelemetry.io/collector/component"
+	"go.opentelemetry.io/collector/config/confighttp"
+	"go.opentelemetry.io/collector/confmap/confmaptest"
+)
+
+func Test_Config_Validate(t *testing.T) {
+	tests := []struct {
+		name    string
+		cfg     *Config
+		wantErr error
+	}{
+		{
+			"valid",
+			func() *Config {
+				return &Config{
+					HTTPServerSettings: confighttp.HTTPServerSettings{
+						Endpoint: "localhost:5678",
+					},
+					Taps: []TapInfo{
+						{
+							Name:     "foo",
+							Endpoint: "localhost:8082",
+						},
+					},
+				}
+			}(),
+			nil,
+		},
+		{
+			"no taps",
+			func() *Config {
+				return &Config{
+					HTTPServerSettings: confighttp.HTTPServerSettings{
+						Endpoint: "localhost:5678",
+					},
+					Taps: []TapInfo{},
+				}
+			}(),
+			errors.New("no taps defined"),
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			err := test.cfg.Validate()
+			if test.wantErr == nil {
+				require.NoError(t, err)
+			} else {
+				require.Equal(t, test.wantErr, err)
+			}
+		})
+	}
+}
+
+func Test_LoadConfig(t *testing.T) {
+	cm, err := confmaptest.LoadConf(filepath.Join("testdata", "config.yaml"))
+	require.NoError(t, err)
+	sub, err := cm.Sub("remotetap")
+	require.NoError(t, err)
+	var cfg Config
+	require.NoError(t, component.UnmarshalConfig(sub, &cfg))
+	require.NoError(t, cfg.Validate())
+}

extension/remotetapextension/extension.go

@@ -6,15 +6,17 @@ package remotetapextension // import "github.com/open-telemetry/opentelemetry-co
 import (
 	"context"
 	"embed"
+	"encoding/json"
 	"errors"
 	"io/fs"
 	"net/http"
 
 	"go.opentelemetry.io/collector/component"
 	"go.opentelemetry.io/collector/extension"
+	"go.uber.org/zap"
 )
 
-//go:embed http/*
+//go:embed html/*
 var httpFS embed.FS
 
 type remoteObserverExtension struct {
@@ -23,21 +25,38 @@ type remoteObserverExtension struct {
 	server   *http.Server
 }
 
-func (s *remoteObserverExtension) Start(_ context.Context, host component.Host) error {
+func (s *remoteObserverExtension) handleTaps(resp http.ResponseWriter, _ *http.Request) {
+	b, err := json.Marshal(s.config.Taps)
+	if err != nil {
+		s.settings.Logger.Error("error marshaling taps info", zap.Error(err))
+		resp.WriteHeader(500)
+	} else {
+		if _, err = resp.Write(b); err != nil {
+			s.settings.Logger.Error("error sending taps info", zap.Error(err))
+		}
+	}
+}
 
+func (s *remoteObserverExtension) Start(_ context.Context, host component.Host) error {
 	htmlContent, err := fs.Sub(httpFS, "html")
 	if err != nil {
 		return err
 	}
 	mux := http.NewServeMux()
 	mux.Handle("/", http.FileServer(http.FS(htmlContent)))
+	mux.HandleFunc("/taps", s.handleTaps)
 	s.server, err = s.config.HTTPServerSettings.ToServer(host, s.settings.TelemetrySettings, mux)
 	if err != nil {
 		return err
 	}
 
+	listener, err := s.config.HTTPServerSettings.ToListener()
+	if err != nil {
+		return err
+	}
+
 	go func() {
-		err := s.server.ListenAndServe()
+		err := s.server.Serve(listener)
 		if err != nil && !errors.Is(err, http.ErrServerClosed) {
 			_ = s.settings.TelemetrySettings.ReportComponentStatus(component.NewFatalErrorEvent(err))
 		}

extension/remotetapextension/extension_test.go

@@ -0,0 +1,64 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package remotetapextension
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+	"go.opentelemetry.io/collector/component/componenttest"
+	"go.opentelemetry.io/collector/config/confighttp"
+)
+
+func Test_handleTaps(t *testing.T) {
+	r := &remoteObserverExtension{
+		config: &Config{Taps: []TapInfo{{
+			Name:     "foo",
+			Endpoint: "localhost:1234",
+		}}},
+	}
+	req := httptest.NewRequest("GET", "/taps", bytes.NewReader([]byte{}))
+	resp := httptest.NewRecorder()
+	r.handleTaps(resp, req)
+	require.Equal(t, 200, resp.Code)
+	b, err := io.ReadAll(resp.Body)
+	require.NoError(t, err)
+	require.Equal(t, `[{"name":"foo","endpoint":"localhost:1234"}]`, string(b))
+}
+
+func Test_ServeHTTP(t *testing.T) {
+	r := &remoteObserverExtension{
+		config: &Config{
+			HTTPServerSettings: confighttp.HTTPServerSettings{
+				Endpoint: defaultEndpoint,
+			},
+			Taps: []TapInfo{{
+				Name:     "foo",
+				Endpoint: "localhost:1234",
+			}}},
+	}
+	err := r.Start(context.Background(), componenttest.NewNopHost())
+	require.NoError(t, err)
+	t.Cleanup(func() {
+		require.NoError(t, r.Shutdown(context.Background()))
+	})
+	time.Sleep(1 * time.Second)
+	client := http.DefaultClient
+	resp, err := client.Get(fmt.Sprintf("http://%s/taps", defaultEndpoint))
+	require.NoError(t, err)
+	b, err := io.ReadAll(resp.Body)
+	require.NoError(t, err)
+	require.Equal(t, `[{"name":"foo","endpoint":"localhost:1234"}]`, string(b))
+
+	resp, err = client.Get(fmt.Sprintf("http://%s/index.js", defaultEndpoint))
+	require.NoError(t, err)
+	require.Equal(t, 200, resp.StatusCode)
+}

extension/remotetapextension/go.mod

@@ -3,12 +3,16 @@ module github.com/open-telemetry/opentelemetry-collector-contrib/extension/remot
 go 1.20
 
 require (
+	github.com/stretchr/testify v1.8.4
 	go.opentelemetry.io/collector/component v0.90.2-0.20231208183206-eed3b4e9c5ef
 	go.opentelemetry.io/collector/config/confighttp v0.90.2-0.20231208183206-eed3b4e9c5ef
+	go.opentelemetry.io/collector/confmap v0.90.2-0.20231208183206-eed3b4e9c5ef
 	go.opentelemetry.io/collector/extension v0.90.2-0.20231208183206-eed3b4e9c5ef
+	go.uber.org/zap v1.26.0
 )
 
 require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/felixge/httpsnoop v1.0.4 // indirect
 	github.com/fsnotify/fsnotify v1.7.0 // indirect
 	github.com/go-logr/logr v1.3.0 // indirect
@@ -24,6 +28,7 @@ require (
 	github.com/mitchellh/copystructure v1.2.0 // indirect
 	github.com/mitchellh/mapstructure v1.5.1-0.20220423185008-bf980b35cac4 // indirect
 	github.com/mitchellh/reflectwalk v1.0.2 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/rs/cors v1.10.1 // indirect
 	go.opentelemetry.io/collector v0.90.2-0.20231208183206-eed3b4e9c5ef // indirect
 	go.opentelemetry.io/collector/config/configauth v0.90.2-0.20231208183206-eed3b4e9c5ef // indirect
@@ -32,7 +37,6 @@ require (
 	go.opentelemetry.io/collector/config/configtelemetry v0.90.2-0.20231208183206-eed3b4e9c5ef // indirect
 	go.opentelemetry.io/collector/config/configtls v0.90.2-0.20231208183206-eed3b4e9c5ef // indirect
 	go.opentelemetry.io/collector/config/internal v0.90.2-0.20231208183206-eed3b4e9c5ef // indirect
-	go.opentelemetry.io/collector/confmap v0.90.2-0.20231208183206-eed3b4e9c5ef // indirect
 	go.opentelemetry.io/collector/extension/auth v0.90.2-0.20231208183206-eed3b4e9c5ef // indirect
 	go.opentelemetry.io/collector/featuregate v1.0.1-0.20231208183206-eed3b4e9c5ef // indirect
 	go.opentelemetry.io/collector/pdata v1.0.1-0.20231208183206-eed3b4e9c5ef // indirect
@@ -41,11 +45,11 @@ require (
 	go.opentelemetry.io/otel/metric v1.21.0 // indirect
 	go.opentelemetry.io/otel/trace v1.21.0 // indirect
 	go.uber.org/multierr v1.11.0 // indirect
-	go.uber.org/zap v1.26.0 // indirect
 	golang.org/x/net v0.19.0 // indirect
 	golang.org/x/sys v0.15.0 // indirect
 	golang.org/x/text v0.14.0 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20230822172742-b8732ec3820d // indirect
 	google.golang.org/grpc v1.59.0 // indirect
 	google.golang.org/protobuf v1.31.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

extension/remotetapextension/html/index.html

@@ -0,0 +1,22 @@
+<!DOCTYPE html>
+<!--
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+-->
+<html lang="en">
+<head>
+  <meta charset="UTF-8">
+  <title>OpenTelemetry Collector Remote Taps Viewer</title>
+</head>
+<body>
+  <h1>OpenTelemetry Collector Remote Taps Viewer</h1>
+  <select id="tap" name="tap">
+  </select>
+  <p>
+    <textarea cols="200" contenteditable="false" id="data" rows="50">
+    </textarea>
+  </p>
+
+  <script src="index.js" type="text/javascript"></script>
+</body>
+</html>