[cmd/opampsupervisor] Implement Collector bootstrapping (#29848)

**Description:**

Utilize the OpAMP extension to get identifying attributes from the
Collector.

A few things I want to call out:
* I moved the Supervisor's various config fragments into separate files
that are embedded into the binary. I think this makes them easier to
edit. I can also move the changes for the existing fragments to a
separate PR if it adds too much to the diff.
* I opted to use the OTLP receiver instead of the filelog receiver
because it is included in both existing upstream distributions and I
expect it is slightly more common. Ideally we should look at other
approaches to solve this.

**Link to tracking Issue:**

Resolves
#21071

**Testing:**

Added an integration test.

---------

Co-authored-by: Antoine Toulme <antoine@toulme.name>
Co-authored-by: Evan Bradley <evan-bradley@users.noreply.github.com>

.chloggen/supervisor-bootstrapping.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: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: cmd/opampsupervisor
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Use a bootstrapping flow to get the Collector's agent description.
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [21071]
+
+# (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: []

cmd/opampsupervisor/e2e_test.go

@@ -15,6 +15,7 @@ import (
 	"net/http"
 	"net/http/httptest"
 	"os"
+	"os/exec"
 	"path"
 	"runtime"
 	"strings"
@@ -23,12 +24,18 @@ import (
 	"text/template"
 	"time"
 
+	"github.com/knadh/koanf/parsers/yaml"
+	"github.com/knadh/koanf/providers/file"
+	"github.com/knadh/koanf/providers/rawbytes"
+	"github.com/knadh/koanf/v2"
 	"github.com/open-telemetry/opamp-go/protobufs"
 	"github.com/open-telemetry/opamp-go/server"
 	"github.com/open-telemetry/opamp-go/server/types"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/cmd/opampsupervisor/supervisor"
+	"github.com/open-telemetry/opentelemetry-collector-contrib/cmd/opampsupervisor/supervisor/config"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	semconv "go.opentelemetry.io/collector/semconv/v1.21.0"
 	"go.uber.org/zap"
 )
 
@@ -122,6 +129,14 @@ func newOpAMPServer(t *testing.T, connectingCallback onConnectingFuncFactory, ca
 }
 
 func newSupervisor(t *testing.T, configType string, extraConfigData map[string]string) *supervisor.Supervisor {
+	cfgFile := getSupervisorConfig(t, configType, extraConfigData)
+	s, err := supervisor.NewSupervisor(zap.NewNop(), cfgFile.Name())
+	require.NoError(t, err)
+
+	return s
+}
+
+func getSupervisorConfig(t *testing.T, configType string, extraConfigData map[string]string) *os.File {
 	tpl, err := os.ReadFile(path.Join("testdata", "supervisor", "supervisor_"+configType+".yaml"))
 	require.NoError(t, err)
 
@@ -148,10 +163,7 @@ func newSupervisor(t *testing.T, configType string, extraConfigData map[string]s
 	_, err = cfgFile.Write(buf.Bytes())
 	require.NoError(t, err)
 
-	s, err := supervisor.NewSupervisor(zap.NewNop(), cfgFile.Name())
-	require.NoError(t, err)
-
-	return s
+	return cfgFile
 }
 
 func TestSupervisorStartsCollectorWithRemoteConfig(t *testing.T) {
@@ -323,6 +335,78 @@ func TestSupervisorConfiguresCapabilities(t *testing.T) {
 	}, 5*time.Second, 250*time.Millisecond)
 }
 
+func TestSupervisorBootstrapsCollector(t *testing.T) {
+	agentDescription := atomic.Value{}
+
+	// Load the Supervisor config so we can get the location of
+	// the Collector that will be run.
+	var cfg config.Supervisor
+	cfgFile := getSupervisorConfig(t, "nocap", map[string]string{})
+	k := koanf.New("::")
+	err := k.Load(file.Provider(cfgFile.Name()), yaml.Parser())
+	require.NoError(t, err)
+	err = k.UnmarshalWithConf("", &cfg, koanf.UnmarshalConf{
+		Tag: "mapstructure",
+	})
+	require.NoError(t, err)
+
+	// Get the binary name and version from the Collector binary
+	// using the `components` command that prints a YAML-encoded
+	// map of information about the Collector build. Some of this
+	// information will be used as defaults for the telemetry
+	// attributes.
+	agentPath := cfg.Agent.Executable
+	componentsInfo, err := exec.Command(agentPath, "components").Output()
+	require.NoError(t, err)
+	k = koanf.New("::")
+	err = k.Load(rawbytes.Provider(componentsInfo), yaml.Parser())
+	require.NoError(t, err)
+	buildinfo := k.StringMap("buildinfo")
+	command := buildinfo["command"]
+	version := buildinfo["version"]
+
+	server := newOpAMPServer(
+		t,
+		defaultConnectingHandler,
+		server.ConnectionCallbacksStruct{
+			OnMessageFunc: func(_ types.Connection, message *protobufs.AgentToServer) *protobufs.ServerToAgent {
+				if message.AgentDescription != nil {
+					agentDescription.Store(message.AgentDescription)
+				}
+
+				return &protobufs.ServerToAgent{}
+			},
+		})
+
+	s := newSupervisor(t, "nocap", map[string]string{"url": server.addr})
+	defer s.Shutdown()
+
+	waitForSupervisorConnection(server.supervisorConnected, true)
+
+	require.Eventually(t, func() bool {
+		ad, ok := agentDescription.Load().(*protobufs.AgentDescription)
+		if !ok {
+			return false
+		}
+
+		var agentName, agentVersion string
+		identAttr := ad.IdentifyingAttributes
+		for _, attr := range identAttr {
+			switch attr.Key {
+			case semconv.AttributeServiceName:
+				agentName = attr.Value.GetStringValue()
+			case semconv.AttributeServiceVersion:
+				agentVersion = attr.Value.GetStringValue()
+			}
+		}
+
+		// By default the Collector should report its name and version
+		// from the component.BuildInfo struct built into the Collector
+		// binary.
+		return agentName == command && agentVersion == version
+	}, 5*time.Second, 250*time.Millisecond)
+}
+
 // Creates a Collector config that reads and writes logs to files and provides
 // file descriptors for I/O operations to those files. The files are placed
 // in a unique temp directory that is cleaned up after the test's completion.

cmd/opampsupervisor/go.mod

@@ -12,6 +12,7 @@ require (
 	github.com/open-telemetry/opamp-go v0.10.0
 	github.com/stretchr/testify v1.8.4
 	go.opentelemetry.io/collector/config/configtls v0.92.1-0.20240110091511-bf804d6c4ecc
+	go.opentelemetry.io/collector/semconv v0.92.1-0.20240110091511-bf804d6c4ecc
 	go.uber.org/zap v1.26.0
 )
 

cmd/opampsupervisor/specification/README.md

@@ -220,8 +220,8 @@ configuration.
 To overcome this problem the Supervisor starts the Collector with an
 "noop" configuration that collects nothing but allows the opamp
 extension to be started. The "noop" configuration is a single pipeline
-with a filelog receiver that points to a non-existing file and a logging
-exporter and the opamp extension. The purpose of the "noop"
+with an OTLP receiver that listens on a random port and a debug
+exporter, and the opamp extension. The purpose of the "noop"
 configuration is to make sure the Collector starts and the opamp
 extension communicates with the Supervisor.
 

cmd/opampsupervisor/supervisor/server.go

@@ -0,0 +1,45 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package supervisor
+
+import (
+	"net/http"
+
+	"github.com/open-telemetry/opamp-go/protobufs"
+	"github.com/open-telemetry/opamp-go/server"
+	serverTypes "github.com/open-telemetry/opamp-go/server/types"
+)
+
+type flattenedSettings struct {
+	onMessageFunc    func(conn serverTypes.Connection, message *protobufs.AgentToServer)
+	onConnectingFunc func(request *http.Request)
+	endpoint         string
+}
+
+func newServerSettings(fs flattenedSettings) server.StartSettings {
+	return server.StartSettings{
+		Settings: server.Settings{
+			Callbacks: server.CallbacksStruct{
+				OnConnectingFunc: func(request *http.Request) serverTypes.ConnectionResponse {
+					if fs.onConnectingFunc != nil {
+						fs.onConnectingFunc(request)
+					}
+					return serverTypes.ConnectionResponse{
+						Accept: true,
+						ConnectionCallbacks: server.ConnectionCallbacksStruct{
+							OnMessageFunc: func(conn serverTypes.Connection, message *protobufs.AgentToServer) *protobufs.ServerToAgent {
+								if fs.onMessageFunc != nil {
+									fs.onMessageFunc(conn, message)
+								}
+
+								return &protobufs.ServerToAgent{}
+							},
+						},
+					}
+				},
+			},
+		},
+		ListenEndpoint: fs.endpoint,
+	}
+}