Stop treating context errors as network errors where possible. (#1045)

GODRIVER-2468
GODRIVER-1965

Author: Benjamin Rewis

mongo/session.go

@@ -200,10 +200,6 @@ func (s *sessionImpl) WithTransaction(ctx context.Context, fn func(sessCtx Sessi
 			default:
 			}
 
-			// End if context has timed out or been canceled, as retrying has no chance of success.
-			if ctx.Err() != nil {
-				return res, err
-			}
 			if errorHasLabel(err, driver.TransientTransactionError) {
 				continue
 			}
@@ -218,10 +214,9 @@ func (s *sessionImpl) WithTransaction(ctx context.Context, fn func(sessCtx Sessi
 	CommitLoop:
 		for {
 			err = s.CommitTransaction(ctx)
-			// End when error is nil (transaction has been committed), or when context has timed out or been
-			// canceled, as retrying has no chance of success.
-			if err == nil || ctx.Err() != nil {
-				return res, err
+			// End when error is nil, as transaction has been committed.
+			if err == nil {
+				return res, nil
 			}
 
 			select {

x/mongo/driver/operation.go

@@ -529,15 +529,17 @@ func (op Operation) Execute(ctx context.Context, scratch []byte) error {
 			serviceID:    startedInfo.serviceID,
 		}
 
-		// Check if there's enough time to perform a round trip before the Context deadline. If ctx is
-		// a Timeout Context, use the 90th percentile RTT as a threshold. Otherwise, use the minimum observed
-		// RTT.
-		if deadline, ok := ctx.Deadline(); ok {
+		// Check for possible context error. If no context error, check if there's enough time to perform a
+		// round trip before the Context deadline. If ctx is a Timeout Context, use the 90th percentile RTT
+		// as a threshold. Otherwise, use the minimum observed RTT.
+		if ctx.Err() != nil {
+			err = ctx.Err()
+		} else if deadline, ok := ctx.Deadline(); ok {
 			if internal.IsTimeoutContext(ctx) && time.Now().Add(srvr.RTT90()).After(deadline) {
 				err = internal.WrapErrorf(ErrDeadlineWouldBeExceeded,
 					"Remaining timeout %v applied from Timeout is less than 90th percentile RTT", time.Until(deadline))
 			} else if time.Now().Add(srvr.MinRTT()).After(deadline) {
-				err = op.networkError(context.DeadlineExceeded)
+				err = context.DeadlineExceeded
 			}
 		}
 

x/mongo/driver/operation_test.go

@@ -605,6 +605,48 @@ func TestOperation(t *testing.T) {
 		assert.Nil(t, err, "ExecuteExhaust error: %v", err)
 		assert.True(t, conn.CurrentlyStreaming(), "expected CurrentlyStreaming to be true")
 	})
+	t.Run("context deadline exceeded not marked as TransientTransactionError", func(t *testing.T) {
+		conn := new(mockConnection)
+		// Create a context that's already timed out.
+		ctx, cancel := context.WithDeadline(context.Background(), time.Unix(893934480, 0))
+		defer cancel()
+
+		op := Operation{
+			Database:   "foobar",
+			Deployment: SingleConnectionDeployment{C: conn},
+			CommandFn: func(dst []byte, desc description.SelectedServer) ([]byte, error) {
+				dst = bsoncore.AppendInt32Element(dst, "ping", 1)
+				return dst, nil
+			},
+		}
+
+		err := op.Execute(ctx, nil)
+		assert.NotNil(t, err, "expected an error from Execute(), got nil")
+		// Assert that error is just context deadline exceeded and is therefore not a driver.Error marked
+		// with the TransientTransactionError label.
+		assert.Equal(t, err, context.DeadlineExceeded, "expected context.DeadlineExceeded error, got %v", err)
+	})
+	t.Run("canceled context not marked as TransientTransactionError", func(t *testing.T) {
+		conn := new(mockConnection)
+		// Create a context and cancel it immediately.
+		ctx, cancel := context.WithCancel(context.Background())
+		cancel()
+
+		op := Operation{
+			Database:   "foobar",
+			Deployment: SingleConnectionDeployment{C: conn},
+			CommandFn: func(dst []byte, desc description.SelectedServer) ([]byte, error) {
+				dst = bsoncore.AppendInt32Element(dst, "ping", 1)
+				return dst, nil
+			},
+		}
+
+		err := op.Execute(ctx, nil)
+		assert.NotNil(t, err, "expected an error from Execute(), got nil")
+		// Assert that error is just context canceled and is therefore not a driver.Error marked with
+		// the TransientTransactionError label.
+		assert.Equal(t, err, context.Canceled, "expected context.Canceled error, got %v", err)
+	})
 }
 
 func createExhaustServerResponse(response bsoncore.Document, moreToCome bool) []byte {

x/mongo/driver/topology/connection.go

@@ -331,11 +331,6 @@ func (c *connection) writeWireMessage(ctx context.Context, wm []byte) error {
 	if atomic.LoadInt64(&c.state) != connConnected {
 		return ConnectionError{ConnectionID: c.id, message: "connection is closed"}
 	}
-	select {
-	case <-ctx.Done():
-		return ConnectionError{ConnectionID: c.id, Wrapped: ctx.Err(), message: "failed to write"}
-	default:
-	}
 
 	var deadline time.Time
 	if c.writeTimeout != 0 {
@@ -388,14 +383,6 @@ func (c *connection) readWireMessage(ctx context.Context, dst []byte) ([]byte, e
 		return dst, ConnectionError{ConnectionID: c.id, message: "connection is closed"}
 	}
 
-	select {
-	case <-ctx.Done():
-		// We closeConnection the connection because we don't know if there is an unread message on the wire.
-		c.close()
-		return nil, ConnectionError{ConnectionID: c.id, Wrapped: ctx.Err(), message: "failed to read"}
-	default:
-	}
-
 	var deadline time.Time
 	if c.readTimeout != 0 {
 		deadline = time.Now().Add(c.readTimeout)

x/mongo/driver/topology/connection_errors_test.go

@@ -50,19 +50,5 @@ func TestConnectionErrors(t *testing.T) {
 			err := conn.connect(ctx)
 			assert.True(t, errors.Is(err, context.Canceled), "expected error %v, got %v", context.Canceled, err)
 		})
-		t.Run("write error", func(t *testing.T) {
-			ctx, cancel := context.WithCancel(context.Background())
-			cancel()
-			conn := &connection{id: "foobar", nc: &net.TCPConn{}, state: connConnected}
-			err := conn.writeWireMessage(ctx, []byte{})
-			assert.True(t, errors.Is(err, context.Canceled), "expected error %v, got %v", context.Canceled, err)
-		})
-		t.Run("read error", func(t *testing.T) {
-			ctx, cancel := context.WithCancel(context.Background())
-			cancel()
-			conn := &connection{id: "foobar", nc: &net.TCPConn{}, state: connConnected}
-			_, err := conn.readWireMessage(ctx, []byte{})
-			assert.True(t, errors.Is(err, context.Canceled), "expected error %v, got %v", context.Canceled, err)
-		})
 	})
 }

x/mongo/driver/topology/connection_test.go

@@ -351,16 +351,6 @@ func TestConnection(t *testing.T) {
 					t.Errorf("errors do not match. got %v; want %v", got, want)
 				}
 			})
-			t.Run("completed context", func(t *testing.T) {
-				ctx, cancel := context.WithCancel(context.Background())
-				cancel()
-				conn := &connection{id: "foobar", nc: &net.TCPConn{}, state: connConnected}
-				want := ConnectionError{ConnectionID: "foobar", Wrapped: ctx.Err(), message: "failed to write"}
-				got := conn.writeWireMessage(ctx, []byte{})
-				if !cmp.Equal(got, want, cmp.Comparer(compareErrors)) {
-					t.Errorf("errors do not match. got %v; want %v", got, want)
-				}
-			})
 			t.Run("deadlines", func(t *testing.T) {
 				testCases := []struct {
 					name        string
@@ -490,16 +480,6 @@ func TestConnection(t *testing.T) {
 					t.Errorf("errors do not match. got %v; want %v", got, want)
 				}
 			})
-			t.Run("completed context", func(t *testing.T) {
-				ctx, cancel := context.WithCancel(context.Background())
-				cancel()
-				conn := &connection{id: "foobar", nc: &net.TCPConn{}, state: connConnected}
-				want := ConnectionError{ConnectionID: "foobar", Wrapped: ctx.Err(), message: "failed to read"}
-				_, got := conn.readWireMessage(ctx, []byte{})
-				if !cmp.Equal(got, want, cmp.Comparer(compareErrors)) {
-					t.Errorf("errors do not match. got %v; want %v", got, want)
-				}
-			})
 			t.Run("deadlines", func(t *testing.T) {
 				testCases := []struct {
 					name        string