From ee9a2ac617b7042c19741837bd27d7283c41de13 Mon Sep 17 00:00:00 2001
From: Paulo Janotti <pjanotti@splunk.com>
Date: Thu, 22 Apr 2021 22:49:15 -0700
Subject: [PATCH] Expose initial and effective config for debugging purposes

(Still incomplete, just the initial ideas)
---
 internal/configprovider/config_server.go      | 145 ++++++++++++++++++
 .../configprovider/config_source_provider.go  |   9 ++
 2 files changed, 154 insertions(+)
 create mode 100644 internal/configprovider/config_server.go

diff --git a/internal/configprovider/config_server.go b/internal/configprovider/config_server.go
new file mode 100644
index 0000000000..f748eb34b3
--- /dev/null
+++ b/internal/configprovider/config_server.go
@@ -0,0 +1,145 @@
+// Copyright Splunk, Inc.
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//       http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package configprovider
+
+import (
+	"net"
+	"net/http"
+	"os"
+	"strings"
+
+	"go.uber.org/zap"
+	"gopkg.in/yaml.v2"
+)
+
+const (
+	defaultEndpoint = "localhost:5555"
+)
+
+type configServer struct {
+	logger    *zap.Logger
+	initial   map[string]interface{}
+	effective map[string]interface{}
+	server    *http.Server
+	doneCh    chan struct{}
+}
+
+func newConfigServer(logger *zap.Logger, initial, effective map[string]interface{}) *configServer {
+	return &configServer{
+		logger:    logger,
+		initial:   initial,
+		effective: effective,
+	}
+}
+
+func (cs *configServer) start() error {
+	endpoint := defaultEndpoint
+	if portOverride, ok := os.LookupEnv("SPLUNK_CONFIG_SERVER_PORT"); ok {
+		if portOverride == "" {
+			// If explicitly set to empty do not start the server.
+			return nil
+		}
+
+		endpoint = "localhost:" + portOverride
+	}
+
+	listener, err := net.Listen("tcp", endpoint)
+	if err != nil {
+		return err
+	}
+
+	mux := http.NewServeMux()
+
+	initialHandleFunc, err := cs.muxHandleFunc(cs.initial)
+	if err != nil {
+		return err
+	}
+	mux.HandleFunc("/debug/configz/initial", initialHandleFunc)
+
+	effectiveHandleFunc, err := cs.muxHandleFunc(simpleRedact(cs.effective))
+	if err != nil {
+		return err
+	}
+	mux.HandleFunc("/debug/configz/effective", effectiveHandleFunc)
+
+	cs.server = &http.Server{
+		Handler: mux,
+	}
+	cs.doneCh = make(chan struct{})
+	go func() {
+		defer close(cs.doneCh)
+
+		if httpErr := cs.server.Serve(listener); httpErr != http.ErrServerClosed {
+			cs.logger.Error("config server error", zap.Error(err))
+		}
+	}()
+
+	return nil
+}
+
+func (cs *configServer) shutdown() error {
+	var err error
+	if cs.server != nil {
+		err = cs.server.Close()
+		// If launched wait for Serve goroutine exit.
+		<-cs.doneCh
+	}
+
+	return err
+}
+
+func (cs *configServer) muxHandleFunc(config map[string]interface{}) (func(http.ResponseWriter, *http.Request), error) {
+	configYAML, err := yaml.Marshal(config)
+	if err != nil {
+		return nil, err
+	}
+
+	return func(writer http.ResponseWriter, request *http.Request) {
+		_, _ = writer.Write(configYAML)
+	}, nil
+}
+
+func simpleRedact(config map[string]interface{}) map[string]interface{} {
+	redactedConfig := make(map[string]interface{})
+	for k, v := range config {
+		switch value := v.(type) {
+		case string:
+			if shouldRedactKey(k) {
+				v = "<redacted>"
+			}
+		case map[string]interface{}:
+			v = simpleRedact(value)
+		}
+
+		redactedConfig[k] = v
+	}
+
+	return redactedConfig
+}
+
+// shouldRedactKey applies a simple check to see if the contents of the given key
+// should be redacted or not.
+func shouldRedactKey(k string) bool {
+	fragments := []string{"access", "auth", "credential", "creds", "login", "password", "pwd", "user"}
+
+	for _, fragment := range fragments {
+		if strings.Contains(k, fragment) {
+			return true
+		}
+	}
+
+	return false
+}
diff --git a/internal/configprovider/config_source_provider.go b/internal/configprovider/config_source_provider.go
index 9329e3eb48..56d74cb4e5 100644
--- a/internal/configprovider/config_source_provider.go
+++ b/internal/configprovider/config_source_provider.go
@@ -30,6 +30,7 @@ type errDuplicatedConfigSourceFactory struct{ error }
 type configSourceParserProvider struct {
 	logger       *zap.Logger
 	csm          *Manager
+	configServer *configServer
 	pp           parserprovider.ParserProvider
 	appStartInfo component.ApplicationStartInfo
 	factories    []Factory
@@ -69,6 +70,11 @@ func (c *configSourceParserProvider) Get() (*config.Parser, error) {
 		return nil, err
 	}
 
+	c.configServer = newConfigServer(c.logger, defaultParser.ToStringMap(), parser.ToStringMap())
+	if err = c.configServer.start(); err != nil {
+		return nil, err
+	}
+
 	c.csm = csm
 	return parser, nil
 }
@@ -82,6 +88,9 @@ func (c *configSourceParserProvider) WatchForUpdate() error {
 // Close ends the watch for updates and closes the parser provider and respective
 // config sources.
 func (c *configSourceParserProvider) Close(ctx context.Context) error {
+	if c.configServer != nil {
+		_ = c.configServer.shutdown()
+	}
 	return c.csm.Close(ctx)
 }