Add livedebugging support for discovery components (#2309)

* Add livedebugging support for discovery components

* Add live debugging for discovery.process

* Simplifying docs

* Update docs/sources/troubleshoot/debug.md

Co-authored-by: Clayton Cornell <131809008+clayton-cornell@users.noreply.github.com>

* typo fix

* Fix test failures

---------

Co-authored-by: Clayton Cornell <131809008+clayton-cornell@users.noreply.github.com>

CHANGELOG.md

@@ -53,6 +53,7 @@ Main (unreleased)
 - Live Debugging button should appear in UI only for supported components (@ravishankar15)
 - Add three new stdlib functions to_base64, from_URLbase64 and to_URLbase64 (@ravishankar15)
 - Add `ignore_older_than` option for local.file_match (@ravishankar15)
+- Add livedebugging support for discovery components (@ravishankar15)
 - Add livedebugging support for `discover.relabel` (@ravishankar15)
 - Performance optimization for live debugging feature (@ravishankar15)
 

docs/sources/troubleshoot/debug.md

@@ -110,7 +110,7 @@ Supported components:
 * `otelcol.processor.*`
 * `otelcol.receiver.*`
 * `prometheus.relabel`
-* `discovery.relabel`
+* `discovery.*`
 {{< /admonition >}}
 
 ## Debug using the UI

internal/component/discovery/discovery.go

@@ -2,6 +2,7 @@ package discovery
 
 import (
 	"context"
+	"fmt"
 	"slices"
 	"sort"
 	"strings"
@@ -15,6 +16,7 @@ import (
 
 	"github.com/grafana/alloy/internal/component"
 	"github.com/grafana/alloy/internal/runtime/logging/level"
+	"github.com/grafana/alloy/internal/service/livedebugging"
 )
 
 // Target refers to a singular discovered endpoint found by a discovery
@@ -74,16 +76,26 @@ type Component struct {
 	latestDisc    DiscovererWithMetrics
 	newDiscoverer chan struct{}
 
-	creator Creator
+	creator            Creator
+	debugDataPublisher livedebugging.DebugDataPublisher
 }
 
+var _ component.Component = (*Component)(nil)
+var _ component.LiveDebugging = (*Component)(nil)
+
 // New creates a discovery component given arguments and a concrete Discovery implementation function.
 func New(o component.Options, args component.Arguments, creator Creator) (*Component, error) {
+	debugDataPublisher, err := o.GetServiceData(livedebugging.ServiceName)
+	if err != nil {
+		return nil, err
+	}
+
 	c := &Component{
 		opts:    o,
 		creator: creator,
 		// buffered to avoid deadlock from the first immediate update
-		newDiscoverer: make(chan struct{}, 1),
+		newDiscoverer:      make(chan struct{}, 1),
+		debugDataPublisher: debugDataPublisher.(livedebugging.DebugDataPublisher),
 	}
 	return c, c.Update(args)
 }
@@ -224,6 +236,10 @@ func (c *Component) runDiscovery(ctx context.Context, d DiscovererWithMetrics) {
 				allTargets = append(allTargets, labels)
 			}
 		}
+		componentID := livedebugging.ComponentID(c.opts.ID)
+		if c.debugDataPublisher.IsActive(componentID) {
+			c.debugDataPublisher.Publish(componentID, fmt.Sprintf("%s", allTargets))
+		}
 		c.opts.OnStateChange(Exports{Targets: allTargets})
 	}
 
@@ -257,3 +273,5 @@ func (c *Component) runDiscovery(ctx context.Context, d DiscovererWithMetrics) {
 		}
 	}
 }
+
+func (c *Component) LiveDebugging(_ int) {}

internal/component/discovery/discovery_test.go

@@ -2,6 +2,7 @@ package discovery
 
 import (
 	"context"
+	"fmt"
 	"os"
 	"sync"
 	"testing"
@@ -14,6 +15,7 @@ import (
 	"github.com/stretchr/testify/require"
 
 	"github.com/grafana/alloy/internal/component"
+	"github.com/grafana/alloy/internal/service/livedebugging"
 )
 
 // discovererUpdateTestCase is a test case for testing discovery updates. A discovery component is created and the
@@ -128,17 +130,28 @@ func TestDiscoveryUpdates(t *testing.T) {
 		t.Run(tc.name, func(t *testing.T) {
 			var publishedExports []component.Exports
 			publishedExportsMut := sync.Mutex{}
-			comp := &Component{
-				opts: component.Options{
-					ID: "discovery.test",
-					OnStateChange: func(e component.Exports) {
-						publishedExportsMut.Lock()
-						defer publishedExportsMut.Unlock()
-						publishedExports = append(publishedExports, e)
-					},
-					Logger: log.NewLogfmtLogger(os.Stdout),
+			opts := component.Options{
+				ID: "discovery.test",
+				OnStateChange: func(e component.Exports) {
+					publishedExportsMut.Lock()
+					defer publishedExportsMut.Unlock()
+					publishedExports = append(publishedExports, e)
+				},
+				Logger: log.NewLogfmtLogger(os.Stdout),
+				GetServiceData: func(name string) (interface{}, error) {
+					switch name {
+					case livedebugging.ServiceName:
+						return livedebugging.NewLiveDebugging(), nil
+					default:
+						return nil, fmt.Errorf("service %q does not exist", name)
+					}
 				},
-				newDiscoverer: make(chan struct{}, 1),
+			}
+			debugDataPublisher, _ := opts.GetServiceData(livedebugging.ServiceName)
+			comp := &Component{
+				opts:               opts,
+				newDiscoverer:      make(chan struct{}, 1),
+				debugDataPublisher: debugDataPublisher.(livedebugging.DebugDataPublisher),
 			}
 
 			discoverer := newFakeDiscoverer()

internal/component/discovery/http/http_test.go

@@ -2,6 +2,7 @@ package http
 
 import (
 	"context"
+	"fmt"
 	"net/http"
 	"net/http/httptest"
 	"net/url"
@@ -19,6 +20,7 @@ import (
 	"github.com/grafana/alloy/internal/component"
 	"github.com/grafana/alloy/internal/component/common/config"
 	"github.com/grafana/alloy/internal/component/discovery"
+	"github.com/grafana/alloy/internal/service/livedebugging"
 	"github.com/grafana/alloy/syntax"
 )
 
@@ -95,6 +97,14 @@ func TestComponent(t *testing.T) {
 				cancel()
 			},
 			Registerer: prometheus.NewRegistry(),
+			GetServiceData: func(name string) (interface{}, error) {
+				switch name {
+				case livedebugging.ServiceName:
+					return livedebugging.NewLiveDebugging(), nil
+				default:
+					return nil, fmt.Errorf("service %q does not exist", name)
+				}
+			},
 		},
 		Arguments{
 			RefreshInterval:  time.Second,

internal/component/discovery/process/process.go

@@ -4,12 +4,14 @@ package process
 
 import (
 	"context"
+	"fmt"
 	"time"
 
 	"github.com/go-kit/log"
 	"github.com/grafana/alloy/internal/component"
 	"github.com/grafana/alloy/internal/component/discovery"
 	"github.com/grafana/alloy/internal/featuregate"
+	"github.com/grafana/alloy/internal/service/livedebugging"
 )
 
 func init() {
@@ -26,24 +28,37 @@ func init() {
 }
 
 func New(opts component.Options, args Arguments) (*Component, error) {
+	debugDataPublisher, err := opts.GetServiceData(livedebugging.ServiceName)
+	if err != nil {
+		return nil, err
+	}
+
 	c := &Component{
-		l:             opts.Logger,
-		onStateChange: opts.OnStateChange,
-		argsUpdates:   make(chan Arguments),
-		args:          args,
+		opts:               opts,
+		l:                  opts.Logger,
+		onStateChange:      opts.OnStateChange,
+		argsUpdates:        make(chan Arguments),
+		args:               args,
+		debugDataPublisher: debugDataPublisher.(livedebugging.DebugDataPublisher),
 	}
 
 	return c, nil
 }
 
 type Component struct {
+	opts          component.Options
 	l             log.Logger
 	onStateChange func(e component.Exports)
 	processes     []discovery.Target
 	argsUpdates   chan Arguments
 	args          Arguments
+
+	debugDataPublisher livedebugging.DebugDataPublisher
 }
 
+var _ component.Component = (*Component)(nil)
+var _ component.LiveDebugging = (*Component)(nil)
+
 func (c *Component) Run(ctx context.Context) error {
 	doDiscover := func() error {
 		processes, err := discover(c.l, &c.args.DiscoverConfig)
@@ -53,6 +68,11 @@ func (c *Component) Run(ctx context.Context) error {
 		c.processes = convertProcesses(processes)
 		c.changed()
 
+		componentID := livedebugging.ComponentID(c.opts.ID)
+		if c.debugDataPublisher.IsActive(componentID) {
+			c.debugDataPublisher.Publish(componentID, fmt.Sprintf("%s", c.processes))
+		}
+
 		return nil
 	}
 	if err := doDiscover(); err != nil {
@@ -88,3 +108,5 @@ func (c *Component) changed() {
 		Targets: join(c.processes, c.args.Join),
 	})
 }
+
+func (c *Component) LiveDebugging(_ int) {}