fix: Add wrapper around libbeat instrumentation to propagate missing …

…tracer config (#13653)

Add wrapper to libbeat instrumentation to propagate missing tracer
config via apm environmental variables.

(cherry picked from commit 0a57bbe)

changelogs/8.15.asciidoc

@@ -33,5 +33,5 @@ https://github.com/elastic/apm-server/compare/v8.14.2\...v8.15.0[View commits]
 - Upgraded bundled APM Java agent attacher CLI to version 1.50.0 {pull}13326[13326]
 - Enable Kibana curated UIs to work with hostmetrics from OpenTelemetry's https://pkg.go.dev/go.opentelemetry.io/collector/receiver/hostmetricsreceiver[hostmetricsreceiver] {pull}13196[13196]
 - Add require data stream to bulk index requests {pull}13398[13398]
-- Support self-instrumentation when in managed mode by getting tracing configs via reloader {pull}13514[13514]
+- Support self-instrumentation when in managed mode by getting tracing configs via reloader {pull}13514[13514] {pull}13653[13653]
 - Add mapping for OpenTelemetry attribute `messaging.destination.name` to derive `service.target` correctly {pull}13472[13472]

internal/beater/beater.go

@@ -292,7 +292,7 @@ func (s *Runner) Run(ctx context.Context) error {
 		}
 	}
 
-	instrumentation, err := instrumentation.New(s.rawConfig, "apm-server", version.Version)
+	instrumentation, err := newInstrumentation(s.rawConfig)
 	if err != nil {
 		return err
 	}
@@ -537,6 +537,57 @@ func (s *Runner) Run(ctx context.Context) error {
 	return errors.Join(result, closeErr)
 }
 
+// newInstrumentation is a thin wrapper around libbeat instrumentation that
+// sets missing tracer configuration from elastic agent.
+func newInstrumentation(rawConfig *agentconfig.C) (instrumentation.Instrumentation, error) {
+	// This config struct contains missing fields from elastic agent APMConfig
+	// https://github.com/elastic/elastic-agent/blob/main/internal/pkg/core/monitoring/config/config.go#L127
+	// that are not directly handled by libbeat instrumentation below.
+	//
+	// Note that original config keys were additionally marshalled by
+	// https://github.com/elastic/elastic-agent/blob/main/pkg/component/runtime/apm_config_mapper.go#L18
+	// that's why the keys are different from the original APMConfig struct.
+	var apmCfg struct {
+		GlobalLabels string `config:"globallabels"`
+		TLS          struct {
+			SkipVerify        bool   `config:"skipverify"`
+			ServerCertificate string `config:"servercert"`
+			ServerCA          string `config:"serverca"`
+		} `config:"tls"`
+	}
+	cfg, err := rawConfig.Child("instrumentation", -1)
+	if err != nil {
+		// Fallback to instrumentation.New if the configs are not present.
+		return instrumentation.New(rawConfig, "apm-server", version.Version)
+	}
+	if err := cfg.Unpack(&apmCfg); err != nil {
+		return nil, err
+	}
+	const (
+		envVerifyServerCert = "ELASTIC_APM_VERIFY_SERVER_CERT"
+		envServerCert       = "ELASTIC_APM_SERVER_CERT"
+		envCACert           = "ELASTIC_APM_SERVER_CA_CERT_FILE"
+		envGlobalLabels     = "ELASTIC_APM_GLOBAL_LABELS"
+	)
+	if apmCfg.TLS.SkipVerify {
+		os.Setenv(envVerifyServerCert, "false")
+		defer os.Unsetenv(envVerifyServerCert)
+	}
+	if apmCfg.TLS.ServerCertificate != "" {
+		os.Setenv(envServerCert, apmCfg.TLS.ServerCertificate)
+		defer os.Unsetenv(envServerCert)
+	}
+	if apmCfg.TLS.ServerCA != "" {
+		os.Setenv(envCACert, apmCfg.TLS.ServerCA)
+		defer os.Unsetenv(envCACert)
+	}
+	if len(apmCfg.GlobalLabels) > 0 {
+		os.Setenv(envGlobalLabels, apmCfg.GlobalLabels)
+		defer os.Unsetenv(envGlobalLabels)
+	}
+	return instrumentation.New(rawConfig, "apm-server", version.Version)
+}
+
 func maxConcurrentDecoders(memLimitGB float64) uint {
 	// Allow 128 concurrent decoders for each 1GB memory, limited to at most 2048.
 	const max = 2048

internal/beater/beater_test.go

@@ -18,11 +18,15 @@
 package beater
 
 import (
+	"compress/zlib"
 	"context"
 	"encoding/json"
+	"encoding/pem"
 	"fmt"
 	"net/http"
 	"net/http/httptest"
+	"os"
+	"path/filepath"
 	"testing"
 	"time"
 
@@ -227,3 +231,43 @@ func TestRunnerNewDocappenderConfig(t *testing.T) {
 		})
 	}
 }
+
+func TestNewInstrumentation(t *testing.T) {
+	labels := make(chan map[string]string, 1)
+	defer close(labels)
+	s := httptest.NewTLSServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Path == "/intake/v2/events" {
+			var b struct {
+				Metadata struct {
+					Labels map[string]string `json:"labels"`
+				} `json:"metadata"`
+			}
+			zr, _ := zlib.NewReader(r.Body)
+			_ = json.NewDecoder(zr).Decode(&b)
+			labels <- b.Metadata.Labels
+		}
+		w.WriteHeader(http.StatusOK)
+	}))
+	defer s.Close()
+	certPath := filepath.Join(t.TempDir(), "cert.pem")
+	f, err := os.Create(certPath)
+	assert.NoError(t, err)
+	err = pem.Encode(f, &pem.Block{Type: "CERTIFICATE", Bytes: s.Certificate().Raw})
+	assert.NoError(t, err)
+	cfg := agentconfig.MustNewConfigFrom(map[string]interface{}{
+		"instrumentation": map[string]interface{}{
+			"enabled": true,
+			"hosts":   []string{s.URL},
+			"tls": map[string]interface{}{
+				"servercert": certPath,
+			},
+			"globallabels": "k1=val,k2=new val",
+		},
+	})
+	i, err := newInstrumentation(cfg)
+	require.NoError(t, err)
+	tracer := i.Tracer()
+	tracer.StartTransaction("name", "type").End()
+	tracer.Flush(nil)
+	assert.Equal(t, map[string]string{"k1": "val", "k2": "new val"}, <-labels)
+}