Require the storage to be explicitly set for persistent queue

Author: Mikołaj Świątek

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### 🛑 Breaking changes 🛑
 
+- Require the storage to be explicitly set for the (experimental) persistent queue (#5784)
 - Remove deprecated funcs/types from service related to `Config` (#5755)
 - Change`confighttp.ToClient` to accept a `component.Host` (#5737)
 - Remove deprecated funcs from pdata related to mutable slices (#5754)

exporter/exporterhelper/README.md

@@ -36,16 +36,13 @@ The following configuration options can be modified:
 With this build tag set, additional configuration option can be enabled:
 
 - `sending_queue`
-  - `persistent_storage_enabled` (default = false): When set, enables persistence via a file storage extension
+  - `storage` (default = none): When set, enables persistence and uses the component specified as a storage extension for the persistent queue
     (note, `enable_unstable` build tag needs to be enabled first, see below for more details)
 
 The maximum number of batches stored to disk can be controlled using `sending_queue.queue_size` parameter (which,
 similarly as for in-memory buffering, defaults to 5000 batches).
 
-When `persistent_storage_enabled` is set to true, the queue is being buffered to disk using 
-[file storage extension](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/extension/storage/filestorage).
-If collector instance is killed while having some items in the persistent queue, on restart the items are being picked and
-the exporting is continued.
+When persistent queue is enabled, the batches are being buffered using the provided storage extension - [filestorage] is a popular and safe choice. If the collector instance is killed while having some items in the persistent queue, on restart the items will be be picked and the exporting is continued.
 
 ```
                                                               ┌─Consumer #1─┐
@@ -93,9 +90,9 @@ exporters:
   otlp:
     endpoint: <ENDPOINT>
     sending_queue:
-      persistent_storage_enabled: true
+      storage: file_storage/otc
 extensions:
-  file_storage:
+  file_storage/otc:
     directory: /var/lib/storage/otc
     timeout: 10s
 service:

exporter/exporterhelper/queued_retry_experimental.go

@@ -44,8 +44,9 @@ type QueueSettings struct {
 	NumConsumers int `mapstructure:"num_consumers"`
 	// QueueSize is the maximum number of batches allowed in queue at a given time.
 	QueueSize int `mapstructure:"queue_size"`
-	// PersistentStorageEnabled describes whether persistence via a file storage extension is enabled
-	PersistentStorageEnabled bool `mapstructure:"persistent_storage_enabled"`
+	// StorageID if not empty, enables the persistent storage and uses the component specified
+	// as a storage extension for the persistent queue
+	StorageID *config.ComponentID `mapstructure:"storage"`
 }
 
 // NewDefaultQueueSettings returns the default settings for QueueSettings.
@@ -57,8 +58,7 @@ func NewDefaultQueueSettings() QueueSettings {
 		// This is a pretty decent value for production.
 		// User should calculate this from the perspective of how many seconds to buffer in case of a backend outage,
 		// multiply that by the number of requests per seconds.
-		QueueSize:                5000,
-		PersistentStorageEnabled: false,
+		QueueSize: 5000,
 	}
 }
 
@@ -76,8 +76,8 @@ func (qCfg *QueueSettings) Validate() error {
 }
 
 var (
-	errNoStorageClient        = errors.New("no storage client extension found")
-	errMultipleStorageClients = errors.New("multiple storage extensions found")
+	errNoStorageClient    = errors.New("no storage client extension found")
+	errWrongExtensionType = errors.New("requested extension is not a storage extension")
 )
 
 type queuedRetrySender struct {
@@ -120,46 +120,54 @@ func newQueuedRetrySender(id config.ComponentID, signal config.DataType, qCfg Qu
 		onTemporaryFailure: qrs.onTemporaryFailure,
 	}
 
-	if !qCfg.PersistentStorageEnabled {
+	if qCfg.StorageID == nil {
 		qrs.queue = internal.NewBoundedMemoryQueue(qrs.cfg.QueueSize, func(item interface{}) {})
 	}
 	// The Persistent Queue is initialized separately as it needs extra information about the component
 
 	return qrs
 }
 
-func getStorageClient(ctx context.Context, host component.Host, id config.ComponentID, signal config.DataType) (*storage.Client, error) {
-	var storageExtension storage.Extension
-	for _, ext := range host.GetExtensions() {
-		if se, ok := ext.(storage.Extension); ok {
-			if storageExtension != nil {
-				return nil, errMultipleStorageClients
+func (qCfg *QueueSettings) getStorageExtension(extensions map[config.ComponentID]component.Extension) (storage.Extension, error) {
+	if qCfg.StorageID != nil {
+		if ext, found := extensions[*qCfg.StorageID]; found {
+			if storageExt, ok := ext.(storage.Extension); ok {
+				return storageExt, nil
 			}
-			storageExtension = se
+			return nil, errWrongExtensionType
 		}
+		return nil, errNoStorageClient
 	}
 
-	if storageExtension == nil {
+	return nil, nil
+}
+
+func (qCfg *QueueSettings) toStorageClient(ctx context.Context, host component.Host, ownerID config.ComponentID, signal config.DataType) (storage.Client, error) {
+	extension, err := qCfg.getStorageExtension(host.GetExtensions())
+	if err != nil {
+		return nil, err
+	}
+	if extension == nil {
 		return nil, errNoStorageClient
 	}
 
-	client, err := storageExtension.GetClient(ctx, component.KindExporter, id, string(signal))
+	client, err := extension.GetClient(ctx, component.KindExporter, ownerID, string(signal))
 	if err != nil {
 		return nil, err
 	}
 
-	return &client, err
+	return client, err
 }
 
 // initializePersistentQueue uses extra information for initialization available from component.Host
 func (qrs *queuedRetrySender) initializePersistentQueue(ctx context.Context, host component.Host) error {
-	if qrs.cfg.PersistentStorageEnabled {
-		storageClient, err := getStorageClient(ctx, host, qrs.id, qrs.signal)
+	if qrs.cfg.StorageID != nil {
+		storageClient, err := qrs.cfg.toStorageClient(ctx, host, qrs.id, qrs.signal)
 		if err != nil {
 			return err
 		}
 
-		qrs.queue = internal.NewPersistentQueue(ctx, qrs.fullName, qrs.signal, qrs.cfg.QueueSize, qrs.logger, *storageClient, qrs.requestUnmarshaler)
+		qrs.queue = internal.NewPersistentQueue(ctx, qrs.fullName, qrs.signal, qrs.cfg.QueueSize, qrs.logger, storageClient, qrs.requestUnmarshaler)
 
 		// TODO: this can be further exposed as a config param rather than relying on a type of queue
 		qrs.requeuingEnabled = true

exporter/exporterhelper/queued_retry_experimental_test.go

@@ -70,7 +70,7 @@ func TestGetRetrySettings(t *testing.T) {
 		desc           string
 		storage        storage.Extension
 		numStorages    int
-		storageEnabled bool
+		storageID      string
 		expectedError  error
 		getClientError error
 	}{
@@ -80,21 +80,21 @@ func TestGetRetrySettings(t *testing.T) {
 			expectedError: errNoStorageClient,
 		},
 		{
-			desc:           "obtain default storage extension",
-			numStorages:    1,
-			storageEnabled: true,
-			expectedError:  nil,
+			desc:          "obtain storage extension by name",
+			numStorages:   2,
+			storageID:     "1",
+			expectedError: nil,
 		},
 		{
-			desc:           "fail on obtaining default storage extension",
-			numStorages:    2,
-			storageEnabled: true,
-			expectedError:  errMultipleStorageClients,
+			desc:          "fail on not existing storage extension",
+			numStorages:   2,
+			storageID:     "100",
+			expectedError: errNoStorageClient,
 		},
 		{
 			desc:           "fail on error getting storage client from extension",
 			numStorages:    1,
-			storageEnabled: true,
+			storageID:      "0",
 			expectedError:  getStorageClientError,
 			getClientError: getStorageClientError,
 		},
@@ -103,6 +103,14 @@ func TestGetRetrySettings(t *testing.T) {
 	for _, tC := range testCases {
 		t.Run(tC.desc, func(t *testing.T) {
 			// prepare
+			cfg := &QueueSettings{
+				Enabled: true,
+			}
+			if tC.storageID != "" {
+				compID := config.NewComponentIDWithName("file_storage", tC.storageID)
+				cfg.StorageID = &compID
+			}
+
 			var extensions = map[config.ComponentID]component.Extension{}
 			for i := 0; i < tC.numStorages; i++ {
 				extensions[config.NewComponentIDWithName("file_storage", strconv.Itoa(i))] = &mockStorageExtension{GetClientError: tC.getClientError}
@@ -111,7 +119,7 @@ func TestGetRetrySettings(t *testing.T) {
 			ownerID := config.NewComponentID("foo_exporter")
 
 			// execute
-			client, err := getStorageClient(context.Background(), host, ownerID, config.TracesDataType)
+			client, err := cfg.toStorageClient(context.Background(), host, ownerID, config.TracesDataType)
 
 			// verify
 			if tC.expectedError != nil {
@@ -182,12 +190,13 @@ func TestQueuedRetryPersistenceEnabled(t *testing.T) {
 	t.Cleanup(func() { require.NoError(t, tt.Shutdown(context.Background())) })
 
 	qCfg := NewDefaultQueueSettings()
-	qCfg.PersistentStorageEnabled = true // enable persistence
+	storageID := config.NewComponentIDWithName("file_storage", "storage")
+	qCfg.StorageID = &storageID // enable persistence
 	rCfg := NewDefaultRetrySettings()
 	be := newBaseExporter(&defaultExporterCfg, tt.ToExporterCreateSettings(), fromOptions(WithRetry(rCfg), WithQueue(qCfg)), "", nopRequestUnmarshaler())
 
 	var extensions = map[config.ComponentID]component.Extension{
-		config.NewComponentIDWithName("file_storage", "storage"): &mockStorageExtension{},
+		storageID: &mockStorageExtension{},
 	}
 	host := &mockHost{ext: extensions}
 
@@ -203,12 +212,13 @@ func TestQueuedRetryPersistenceEnabledStorageError(t *testing.T) {
 	t.Cleanup(func() { require.NoError(t, tt.Shutdown(context.Background())) })
 
 	qCfg := NewDefaultQueueSettings()
-	qCfg.PersistentStorageEnabled = true // enable persistence
+	storageID := config.NewComponentIDWithName("file_storage", "storage")
+	qCfg.StorageID = &storageID // enable persistence
 	rCfg := NewDefaultRetrySettings()
 	be := newBaseExporter(&defaultExporterCfg, tt.ToExporterCreateSettings(), fromOptions(WithRetry(rCfg), WithQueue(qCfg)), "", nopRequestUnmarshaler())
 
 	var extensions = map[config.ComponentID]component.Extension{
-		config.NewComponentIDWithName("file_storage", "storage"): &mockStorageExtension{GetClientError: storageError},
+		storageID: &mockStorageExtension{GetClientError: storageError},
 	}
 	host := &mockHost{ext: extensions}