Make sanitize_field_names centrally configurable

CHANGELOG.asciidoc

@@ -24,6 +24,8 @@ endif::[]
 https://github.com/elastic/apm-agent-go/compare/v1.9.0...master[View commits]
 
 - module/apmsql: add tracingDriver.Unwrap method to get underlying driver {pull}#849[#(849)]
+- module/apmgopgv10: add support for github.com/go-pg/pg/v10 {pull}857[(#857)]
+- Enable central configuration of "sanitize_field_names" {pull}856[(#856)]
 
 [[release-notes-1.x]]
 === Go Agent version 1.x

config.go

@@ -358,6 +358,11 @@ func (t *Tracer) updateRemoteConfig(logger WarningLogger, old, attrs map[string]
 					cfg.recording = recording
 				})
 			}
+		case envSanitizeFieldNames:
+			matchers := configutil.ParseWildcardPatterns(v)
+			updates = append(updates, func(cfg *instrumentationConfig) {
+				cfg.sanitizedFieldNames = matchers
+			})
 		case envSpanFramesMinDuration:
 			duration, err := configutil.ParseDuration(v)
 			if err != nil {
@@ -487,4 +492,5 @@ type instrumentationConfigValues struct {
 	spanFramesMinDuration time.Duration
 	stackTraceLimit       int
 	propagateLegacyHeader bool
+	sanitizedFieldNames   wildcard.Matchers
 }

config_test.go

@@ -83,6 +83,20 @@ func TestTracerCentralConfigUpdate(t *testing.T) {
 		assert.Len(t, payloads.Errors, 1)
 		return len(payloads.Errors[0].Exception.Stacktrace) == 1
 	})
+	run("sanitize_field_names", "secret", func(tracer *apmtest.RecordingTracer) bool {
+		tracer.ResetPayloads()
+		tracer.SetSanitizedFieldNames("not_secret")
+		req, _ := http.NewRequest("GET", "http://server.testing/", nil)
+		req.AddCookie(&http.Cookie{Name: "secret", Value: "top"})
+		tx := tracer.StartTransaction("name", "type")
+		tx.Context.SetHTTPRequest(req)
+		tx.End()
+		tracer.Flush(nil)
+		payloads := tracer.Payloads()
+		assert.Len(t, payloads.Transactions, 1)
+		assert.Len(t, payloads.Transactions[0].Context.Request.Cookies, 1)
+		return payloads.Transactions[0].Context.Request.Cookies[0].Value == "[REDACTED]"
+	})
 }
 
 func testTracerCentralConfigUpdate(t *testing.T, serverResponse string, isRemote func(*apmtest.RecordingTracer) bool) {

modelwriter.go

@@ -126,12 +126,12 @@ func (w *modelWriter) buildModelTransaction(out *model.Transaction, tx *Transact
 		out.Context = td.Context.build()
 	}
 
-	if len(w.cfg.sanitizedFieldNames) != 0 && out.Context != nil {
+	if len(td.sanitizedFieldNames) != 0 && out.Context != nil {
 		if out.Context.Request != nil {
-			sanitizeRequest(out.Context.Request, w.cfg.sanitizedFieldNames)
+			sanitizeRequest(out.Context.Request, td.sanitizedFieldNames)
 		}
 		if out.Context.Response != nil {
-			sanitizeResponse(out.Context.Response, w.cfg.sanitizedFieldNames)
+			sanitizeResponse(out.Context.Response, td.sanitizedFieldNames)
 		}
 	}
 }

tracer.go

@@ -423,6 +423,9 @@ func newTracer(opts TracerOptions) *Tracer {
 	t.setLocalInstrumentationConfig(envUseElasticTraceparentHeader, func(cfg *instrumentationConfigValues) {
 		cfg.propagateLegacyHeader = opts.propagateLegacyHeader
 	})
+	t.setLocalInstrumentationConfig(envSanitizeFieldNames, func(cfg *instrumentationConfigValues) {
+		cfg.sanitizedFieldNames = opts.sanitizedFieldNames
+	})
 
 	if !opts.active {
 		t.active = 0
@@ -439,7 +442,6 @@ func newTracer(opts TracerOptions) *Tracer {
 		cfg.metricsInterval = opts.metricsInterval
 		cfg.requestDuration = opts.requestDuration
 		cfg.requestSize = opts.requestSize
-		cfg.sanitizedFieldNames = opts.sanitizedFieldNames
 		cfg.disabledMetrics = opts.disabledMetrics
 		cfg.preContext = defaultPreContext
 		cfg.postContext = defaultPostContext
@@ -465,7 +467,6 @@ type tracerConfig struct {
 	metricsGatherers        []MetricsGatherer
 	contextSetter           stacktrace.ContextSetter
 	preContext, postContext int
-	sanitizedFieldNames     wildcard.Matchers
 	disabledMetrics         wildcard.Matchers
 	cpuProfileDuration      time.Duration
 	cpuProfileInterval      time.Duration
@@ -572,6 +573,10 @@ func (t *Tracer) SetLogger(logger Logger) {
 // of the the supplied patterns will have their values redacted. If
 // SetSanitizedFieldNames is called with no arguments, then no fields
 // will be redacted.
+//
+// Configuration via Kibana takes precedence over local configuration, so
+// if sanitized_field_names has been configured via Kibana, this call will
+// not have any effect until/unless that configuration has been removed.
 func (t *Tracer) SetSanitizedFieldNames(patterns ...string) error {
 	var matchers wildcard.Matchers
 	if len(patterns) != 0 {
@@ -580,7 +585,7 @@ func (t *Tracer) SetSanitizedFieldNames(patterns ...string) error {
 			matchers[i] = configutil.ParseWildcardPattern(p)
 		}
 	}
-	t.sendConfigCommand(func(cfg *tracerConfig) {
+	t.setLocalInstrumentationConfig(envSanitizeFieldNames, func(cfg *instrumentationConfigValues) {
 		cfg.sanitizedFieldNames = matchers
 	})
 	return nil

transaction.go

@@ -23,6 +23,8 @@ import (
 	"math/rand"
 	"sync"
 	"time"
+
+	"go.elastic.co/apm/internal/wildcard"
 )
 
 // StartTransaction returns a new Transaction with the specified
@@ -66,6 +68,7 @@ func (t *Tracer) StartTransactionOptions(name, transactionType string, opts Tran
 	tx.stackTraceLimit = instrumentationConfig.stackTraceLimit
 	tx.Context.captureHeaders = instrumentationConfig.captureHeaders
 	tx.propagateLegacyHeader = instrumentationConfig.propagateLegacyHeader
+	tx.sanitizedFieldNames = instrumentationConfig.sanitizedFieldNames
 	tx.breakdownMetricsEnabled = t.breakdownMetrics.enabled
 
 	var root bool
@@ -343,6 +346,7 @@ type TransactionData struct {
 	stackTraceLimit         int
 	breakdownMetricsEnabled bool
 	propagateLegacyHeader   bool
+	sanitizedFieldNames     wildcard.Matchers
 	timestamp               time.Time
 
 	mu            sync.Mutex