Expand central config support

capturebody.go

@@ -69,9 +69,7 @@ func (t *Tracer) CaptureHTTPRequestBody(req *http.Request) *BodyCapturer {
 	if req.Body == nil {
 		return nil
 	}
-	t.captureBodyMu.RLock()
-	captureBody := t.captureBody
-	t.captureBodyMu.RUnlock()
+	captureBody := t.instrumentationConfig().captureBody
 	if captureBody == CaptureBodyOff {
 		return nil
 	}

env.go → config.go

@@ -23,7 +23,9 @@ import (
 	"runtime"
 	"strconv"
 	"strings"
+	"sync/atomic"
 	"time"
+	"unsafe"
 
 	"github.com/pkg/errors"
 
@@ -203,6 +205,10 @@ func initialCaptureBody() (CaptureBodyMode, error) {
 	if value == "" {
 		return defaultCaptureBody, nil
 	}
+	return parseCaptureBody(envCaptureBody, value)
+}
+
+func parseCaptureBody(name, value string) (CaptureBodyMode, error) {
 	switch strings.TrimSpace(strings.ToLower(value)) {
 	case "all":
 		return CaptureBodyAll, nil
@@ -213,7 +219,7 @@ func initialCaptureBody() (CaptureBodyMode, error) {
 	case "off":
 		return CaptureBodyOff, nil
 	}
-	return -1, errors.Errorf("invalid %s value %q", envCaptureBody, value)
+	return -1, errors.Errorf("invalid %s value %q", name, value)
 }
 
 func initialService() (name, version, environment string) {
@@ -261,3 +267,153 @@ func initialCentralConfigEnabled() (bool, error) {
 func initialBreakdownMetricsEnabled() (bool, error) {
 	return configutil.ParseBoolEnv(envBreakdownMetrics, true)
 }
+
+// updateRemoteConfig updates t and cfg with changes held in "attrs", and reverts to local
+// config for config attributes that have been removed (exist in old but not in attrs).
+//
+// On return from updateRemoteConfig, unapplied config will have been removed from attrs.
+func (t *Tracer) updateRemoteConfig(logger WarningLogger, old, attrs map[string]string) {
+	warningf := func(string, ...interface{}) {}
+	debugf := func(string, ...interface{}) {}
+	errorf := func(string, ...interface{}) {}
+	if logger != nil {
+		warningf = logger.Warningf
+		debugf = logger.Debugf
+		errorf = logger.Errorf
+	}
+	envName := func(k string) string {
+		return "ELASTIC_APM_" + strings.ToUpper(k)
+	}
+
+	var updates []func(cfg *instrumentationConfig)
+	for k, v := range attrs {
+		if oldv, ok := old[k]; ok && oldv == v {
+			continue
+		}
+		switch envName(k) {
+		case envCaptureBody:
+			value, err := parseCaptureBody(k, v)
+			if err != nil {
+				errorf("central config failure: %s", err)
+				delete(attrs, k)
+				continue
+			} else {
+				updates = append(updates, func(cfg *instrumentationConfig) {
+					cfg.captureBody = value
+				})
+			}
+		case envMaxSpans:
+			value, err := strconv.Atoi(v)
+			if err != nil {
+				errorf("central config failure: failed to parse %s: %s", k, err)
+				delete(attrs, k)
+				continue
+			} else {
+				updates = append(updates, func(cfg *instrumentationConfig) {
+					cfg.maxSpans = value
+				})
+			}
+		case envTransactionSampleRate:
+			sampler, err := parseSampleRate(k, v)
+			if err != nil {
+				errorf("central config failure: %s", err)
+				delete(attrs, k)
+				continue
+			} else {
+				updates = append(updates, func(cfg *instrumentationConfig) {
+					cfg.sampler = sampler
+				})
+			}
+		default:
+			warningf("central config failure: unsupported config: %s", k)
+			delete(attrs, k)
+			continue
+		}
+		debugf("central config update: updated %s to %s", k, v)
+	}
+	for k := range old {
+		if _, ok := attrs[k]; ok {
+			continue
+		}
+		updates = append(updates, func(cfg *instrumentationConfig) {
+			if f, ok := cfg.local[envName(k)]; ok {
+				f(&cfg.instrumentationConfigValues)
+			}
+		})
+		debugf("central config update: reverted %s to local config", k)
+	}
+	if updates != nil {
+		remote := make(map[string]struct{})
+		for k := range attrs {
+			remote[envName(k)] = struct{}{}
+		}
+		t.updateInstrumentationConfig(func(cfg *instrumentationConfig) {
+			cfg.remote = remote
+			for _, update := range updates {
+				update(cfg)
+			}
+		})
+	}
+}
+
+// instrumentationConfig returns the current instrumentationConfig.
+//
+// The returned value is immutable.
+func (t *Tracer) instrumentationConfig() *instrumentationConfig {
+	config := atomic.LoadPointer((*unsafe.Pointer)(unsafe.Pointer(&t.instrumentationConfigInternal)))
+	return (*instrumentationConfig)(config)
+}
+
+// setLocalInstrumentationConfig sets local transaction configuration with
+// the specified environment variable key.
+func (t *Tracer) setLocalInstrumentationConfig(envKey string, f func(cfg *instrumentationConfigValues)) {
+	t.updateInstrumentationConfig(func(cfg *instrumentationConfig) {
+		cfg.local[envKey] = f
+		if _, ok := cfg.remote[envKey]; !ok {
+			f(&cfg.instrumentationConfigValues)
+		}
+	})
+}
+
+func (t *Tracer) updateInstrumentationConfig(f func(cfg *instrumentationConfig)) {
+	for {
+		oldConfig := t.instrumentationConfig()
+		newConfig := *oldConfig
+		f(&newConfig)
+		if atomic.CompareAndSwapPointer(
+			(*unsafe.Pointer)(unsafe.Pointer(&t.instrumentationConfigInternal)),
+			unsafe.Pointer(oldConfig),
+			unsafe.Pointer(&newConfig),
+		) {
+			return
+		}
+	}
+}
+
+// instrumentationConfig holds current configuration values, as well as information
+// required to revert from remote to local configuration.
+type instrumentationConfig struct {
+	instrumentationConfigValues
+
+	// local holds functions for setting instrumentationConfigValues to the most
+	// recently, locally specified configuration.
+	local map[string]func(*instrumentationConfigValues)
+
+	// remote holds the environment variable keys for applied remote config.
+	remote map[string]struct{}
+}
+
+// instrumentationConfigValues holds configuration that is accessible outside of the
+// tracer loop, for instrumentation: StartTransaction, StartSpan, CaptureError, etc.
+//
+// NOTE(axw) when adding configuration here, you must also update `newTracer` to
+// set the initial entry in instrumentationConfig.local, in order to properly reset
+// to the local value, even if the default is the zero value.
+type instrumentationConfigValues struct {
+	captureBody           CaptureBodyMode
+	captureHeaders        bool
+	maxSpans              int
+	sampler               Sampler
+	spanFramesMinDuration time.Duration
+	stackTraceLimit       int
+}