GODRIVER-2672 Return ServerError with "TransientTransactionError" label for server selection timeouts. (#1198)

Author: qingyang-hu

mongo/database_test.go

@@ -10,6 +10,7 @@ import (
 	"context"
 	"errors"
 	"testing"
+	"time"
 
 	"go.mongodb.org/mongo-driver/bson"
 	"go.mongodb.org/mongo-driver/bson/bsoncodec"
@@ -18,6 +19,7 @@ import (
 	"go.mongodb.org/mongo-driver/mongo/readconcern"
 	"go.mongodb.org/mongo-driver/mongo/readpref"
 	"go.mongodb.org/mongo-driver/mongo/writeconcern"
+	"go.mongodb.org/mongo-driver/x/mongo/driver/topology"
 )
 
 func setupDb(name string, opts ...*options.DatabaseOptions) *Database {
@@ -84,7 +86,6 @@ func TestDatabase(t *testing.T) {
 	})
 	t.Run("replace topology error", func(t *testing.T) {
 		db := setupDb("foo")
-
 		err := db.RunCommand(bgCtx, bson.D{{"x", 1}}).Err()
 		assert.Equal(t, ErrClientDisconnected, err, "expected error %v, got %v", ErrClientDisconnected, err)
 
@@ -94,6 +95,43 @@ func TestDatabase(t *testing.T) {
 		_, err = db.ListCollections(bgCtx, bson.D{})
 		assert.Equal(t, ErrClientDisconnected, err, "expected error %v, got %v", ErrClientDisconnected, err)
 	})
+	t.Run("TransientTransactionError label", func(t *testing.T) {
+		client := setupClient(options.Client().ApplyURI("mongodb://nonexistent").SetServerSelectionTimeout(3 * time.Second))
+		err := client.Connect(bgCtx)
+		defer client.Disconnect(bgCtx)
+		assert.Nil(t, err, "expected nil, got %v", err)
+
+		t.Run("negative case of non-transaction", func(t *testing.T) {
+			var sse topology.ServerSelectionError
+			var le LabeledError
+
+			err := client.Ping(bgCtx, nil)
+			assert.NotNil(t, err, "expected error, got nil")
+			assert.True(t, errors.As(err, &sse), `expected error to be a "topology.ServerSelectionError"`)
+			if errors.As(err, &le) {
+				assert.False(t, le.HasErrorLabel("TransientTransactionError"), `expected error not to include the "TransientTransactionError" label`)
+			}
+		})
+
+		t.Run("positive case of transaction", func(t *testing.T) {
+			var sse topology.ServerSelectionError
+			var le LabeledError
+
+			sess, err := client.StartSession()
+			assert.Nil(t, err, "expected nil, got %v", err)
+			defer sess.EndSession(bgCtx)
+
+			sessCtx := NewSessionContext(bgCtx, sess)
+			err = sess.StartTransaction()
+			assert.Nil(t, err, "expected nil, got %v", err)
+
+			err = client.Ping(sessCtx, nil)
+			assert.NotNil(t, err, "expected error, got nil")
+			assert.True(t, errors.As(err, &sse), `expected error to be a "topology.ServerSelectionError"`)
+			assert.True(t, errors.As(err, &le), `expected error to implement the "LabeledError" interface`)
+			assert.True(t, le.HasErrorLabel("TransientTransactionError"), `expected error to include the "TransientTransactionError" label`)
+		})
+	})
 	t.Run("nil document error", func(t *testing.T) {
 		db := setupDb("foo")
 

mongo/errors.go

@@ -129,7 +129,7 @@ func IsTimeout(err error) bool {
 			return ne.Timeout()
 		}
 		//timeout error labels
-		if le, ok := err.(labeledError); ok {
+		if le, ok := err.(LabeledError); ok {
 			if le.HasErrorLabel("NetworkTimeoutError") || le.HasErrorLabel("ExceededTimeLimitError") {
 				return true
 			}
@@ -153,7 +153,7 @@ func unwrap(err error) error {
 // errorHasLabel returns true if err contains the specified label
 func errorHasLabel(err error, label string) bool {
 	for ; err != nil; err = unwrap(err) {
-		if le, ok := err.(labeledError); ok && le.HasErrorLabel(label) {
+		if le, ok := err.(LabeledError); ok && le.HasErrorLabel(label) {
 			return true
 		}
 	}
@@ -207,7 +207,8 @@ func (e MongocryptdError) Unwrap() error {
 	return e.Wrapped
 }
 
-type labeledError interface {
+// LabeledError is an interface for errors with labels.
+type LabeledError interface {
 	error
 	// HasErrorLabel returns true if the error contains the specified label.
 	HasErrorLabel(string) bool
@@ -216,11 +217,9 @@ type labeledError interface {
 // ServerError is the interface implemented by errors returned from the server. Custom implementations of this
 // interface should not be used in production.
 type ServerError interface {
-	error
+	LabeledError
 	// HasErrorCode returns true if the error has the specified code.
 	HasErrorCode(int) bool
-	// HasErrorLabel returns true if the error contains the specified label.
-	HasErrorLabel(string) bool
 	// HasErrorMessage returns true if the error contains the specified message.
 	HasErrorMessage(string) bool
 	// HasErrorCodeWithMessage returns true if any of the contained errors have the specified code and message.

x/mongo/driver/operation.go

@@ -319,6 +319,14 @@ func (op Operation) selectServer(ctx context.Context) (Server, error) {
 func (op Operation) getServerAndConnection(ctx context.Context) (Server, Connection, error) {
 	server, err := op.selectServer(ctx)
 	if err != nil {
+		if op.Client != nil &&
+			!(op.Client.Committing || op.Client.Aborting) && op.Client.TransactionRunning() {
+			err = Error{
+				Message: err.Error(),
+				Labels:  []string{TransientTransactionError},
+				Wrapped: err,
+			}
+		}
 		return nil, nil, err
 	}