Remove race condition when accessing remote bulker map (#4171)

Use the remoteOutputMutex whenever accessing the bulkerMap.
Change GetBulkerMap to return a copy of the map so that remote output health will not conflict with adding/removing a bulker from the map.

Author: michel-laterman

changelog/fragments/1733181546-Remove-race-in-remote-bulker-access.yaml

@@ -0,0 +1,32 @@
+# Kind can be one of:
+# - breaking-change: a change to previously-documented behavior
+# - deprecation: functionality that is being removed in a later release
+# - bug-fix: fixes a problem in a previous version
+# - enhancement: extends functionality but does not break or fix existing behavior
+# - feature: new functionality
+# - known-issue: problems that we are aware of in a given version
+# - security: impacts on the security of a product or a user’s deployment.
+# - upgrade: important information for someone upgrading from a prior version
+# - other: does not fit into any of the other categories
+kind: bug-fix
+
+# Change summary; a 80ish characters long description of the change.
+summary: Remove race in remote bulker access
+
+# Long description; in case the summary is not enough to describe the change
+# this field accommodate a description without length limits.
+# NOTE: This field will be rendered only for breaking-change and known-issue kinds at the moment.
+#description:
+
+# Affected component; usually one of "elastic-agent", "fleet-server", "filebeat", "metricbeat", "auditbeat", "all", etc.
+component: fleet-server
+
+# PR URL; optional; the PR number that added the changeset.
+# If not present is automatically filled by the tooling finding the PR where this changelog fragment has been added.
+# NOTE: the tooling supports backports, so it's able to fill the original PR number instead of the backport PR number.
+# Please provide it if you are adding a fragment for a different PR.
+#pr: https://github.com/owner/repo/1234
+
+# Issue URL; optional; the GitHub issue related to this changeset (either closes or is part of).
+# If not present is automatically filled by the tooling with the issue linked to the PR number.
+issue: https://github.com/elastic/fleet-server/issues/4170

internal/pkg/bulk/bulk_remote_output_test.go

@@ -12,6 +12,8 @@ import (
 
 	"github.com/rs/zerolog"
 	"github.com/stretchr/testify/assert"
+
+	testlog "github.com/elastic/fleet-server/v7/internal/pkg/testing/log"
 )
 
 func Test_hasChangedAndUpdateRemoteOutputConfig(t *testing.T) {
@@ -78,9 +80,10 @@ func Test_hasChangedAndUpdateRemoteOutputConfig(t *testing.T) {
 
 	for _, tc := range testcases {
 		t.Run(tc.name, func(t *testing.T) {
+			log := testlog.SetLogger(t)
 			bulker := NewBulker(nil, nil)
 			bulker.remoteOutputConfigMap["remote1"] = tc.cfg
-			hasChanged := bulker.hasChangedAndUpdateRemoteOutputConfig(zerolog.Nop(), "remote1", tc.newCfg)
+			hasChanged := bulker.hasChangedAndUpdateRemoteOutputConfig(log, "remote1", tc.newCfg)
 			assert.Equal(t, tc.changed, hasChanged)
 			assert.Equal(t, tc.newCfg, bulker.remoteOutputConfigMap["remote1"])
 		})
@@ -148,3 +151,57 @@ func Test_CreateAndGetBulkerChanged(t *testing.T) {
 	assert.Nil(t, err)
 	assert.Equal(t, true, cancelFnCalled)
 }
+
+func Benchmark_CreateAndGetBulker(b *testing.B) {
+	b.Skip("Crashes on remote runner")
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	log := zerolog.Nop()
+	outputMap := map[string]map[string]any{
+		"remote1": map[string]any{
+			"type":          "remote_elasticsearch",
+			"hosts":         []interface{}{"https://remote-es:443"},
+			"service_token": "token1",
+		},
+	}
+	b.Run("new remote bulker", func(b *testing.B) {
+		bulker := NewBulker(nil, nil)
+		b.ReportAllocs()
+		for range b.N {
+			b.StopTimer()
+			bulker.bulkerMap = make(map[string]Bulk)
+			bulker.remoteOutputConfigMap = make(map[string]map[string]any)
+			b.StartTimer()
+
+			bulker.CreateAndGetBulker(ctx, log, "remote1", outputMap)
+		}
+	})
+	b.Run("existing remote bulker", func(b *testing.B) {
+		bulker := NewBulker(nil, nil)
+		outputBulker := NewBulker(nil, nil)
+		bulker.bulkerMap["remote1"] = outputBulker
+		bulker.remoteOutputConfigMap["remote1"] = outputMap["remote1"]
+		b.ResetTimer()
+		b.ReportAllocs()
+		for range b.N {
+			bulker.CreateAndGetBulker(ctx, log, "remote1", outputMap)
+		}
+	})
+	b.Run("changed remote bulker", func(b *testing.B) {
+		b.ReportAllocs()
+		for range b.N {
+			b.StopTimer()
+			bulker := NewBulker(nil, nil)
+			outputBulker := NewBulker(nil, nil)
+			bulker.bulkerMap["remote1"] = outputBulker
+			bulker.remoteOutputConfigMap["remote1"] = map[string]any{
+				"type":          "remote_elasticsearch",
+				"hosts":         []interface{}{"https://remote-es:443"},
+				"service_token": "wrong token",
+			}
+			b.StartTimer()
+
+			bulker.CreateAndGetBulker(ctx, log, "remote1", outputMap)
+		}
+	})
+}

internal/pkg/bulk/engine.go

@@ -130,11 +130,20 @@ func NewBulker(es esapi.Transport, tracer *apm.Tracer, opts ...BulkOpt) *Bulker
 }
 
 func (b *Bulker) GetBulker(outputName string) Bulk {
+	b.remoteOutputMutex.RLock()
+	defer b.remoteOutputMutex.RUnlock()
 	return b.bulkerMap[outputName]
 }
 
+// GetBulkerMap returns a copy of the remote output bulkers
 func (b *Bulker) GetBulkerMap() map[string]Bulk {
-	return b.bulkerMap
+	mp := make(map[string]Bulk)
+	b.remoteOutputMutex.RLock()
+	for k, v := range b.bulkerMap {
+		mp[k] = v
+	}
+	b.remoteOutputMutex.RUnlock()
+	return mp
 }
 
 func (b *Bulker) CancelFn() context.CancelFunc {
@@ -155,7 +164,9 @@ func (b *Bulker) updateBulkerMap(outputName string, newBulker *Bulker) {
 // if changed, stop the existing bulker and create a new one
 func (b *Bulker) CreateAndGetBulker(ctx context.Context, zlog zerolog.Logger, outputName string, outputMap map[string]map[string]interface{}) (Bulk, bool, error) {
 	hasConfigChanged := b.hasChangedAndUpdateRemoteOutputConfig(zlog, outputName, outputMap[outputName])
+	b.remoteOutputMutex.RLock()
 	bulker := b.bulkerMap[outputName]
+	b.remoteOutputMutex.RUnlock()
 	if bulker != nil && !hasConfigChanged {
 		return bulker, false, nil
 	}
@@ -429,6 +440,8 @@ func (b *Bulker) Run(ctx context.Context) error {
 
 	// cancelling context of each remote bulker when Run exits
 	defer func() {
+		b.remoteOutputMutex.RLock()
+		defer b.remoteOutputMutex.RUnlock()
 		for _, bulker := range b.bulkerMap {
 			bulker.CancelFn()()
 		}