GODRIVER-2531 Return canceled error message when canceled for waiting connection in wait queue. (#1058)

Author: proost

x/mongo/driver/topology/errors.go

@@ -7,6 +7,7 @@
 package topology
 
 import (
+	"context"
 	"fmt"
 
 	"go.mongodb.org/mongo-driver/mongo/description"
@@ -78,8 +79,20 @@ type WaitQueueTimeoutError struct {
 // Error implements the error interface.
 func (w WaitQueueTimeoutError) Error() string {
 	errorMsg := "timed out while checking out a connection from connection pool"
-	if w.Wrapped != nil {
-		errorMsg = fmt.Sprintf("%s: %s", errorMsg, w.Wrapped.Error())
+	switch w.Wrapped {
+	case nil:
+	case context.Canceled:
+		errorMsg = fmt.Sprintf(
+			"%s: %s",
+			"canceled while checking out a connection from connection pool",
+			w.Wrapped.Error(),
+		)
+	default:
+		errorMsg = fmt.Sprintf(
+			"%s: %s",
+			errorMsg,
+			w.Wrapped.Error(),
+		)
 	}
 
 	return fmt.Sprintf(

x/mongo/driver/topology/pool_test.go

@@ -645,6 +645,7 @@ func TestPool(t *testing.T) {
 			assert.IsTypef(t, WaitQueueTimeoutError{}, err, "expected a WaitQueueTimeoutError")
 			if err, ok := err.(WaitQueueTimeoutError); ok {
 				assert.Equalf(t, context.DeadlineExceeded, err.Unwrap(), "expected wrapped error to be a context.Timeout")
+				assert.Containsf(t, err.Error(), "timed out", `expected error message to contain "timed out"`)
 			}
 
 			p.close(context.Background())
@@ -773,6 +774,42 @@ func TestPool(t *testing.T) {
 			assert.Equalf(t, 2, p.totalConnectionCount(), "pool should have 2 total connection")
 			assert.Equalf(t, 0, p.availableConnectionCount(), "pool should have 0 idle connection")
 
+			p.close(context.Background())
+		})
+		t.Run("canceled context in wait queue", func(t *testing.T) {
+			t.Parallel()
+
+			cleanup := make(chan struct{})
+			defer close(cleanup)
+			addr := bootstrapConnections(t, 1, func(nc net.Conn) {
+				<-cleanup
+				_ = nc.Close()
+			})
+
+			p := newPool(poolConfig{
+				Address:     address.Address(addr.String()),
+				MaxPoolSize: 1,
+			})
+			err := p.ready()
+			noerr(t, err)
+
+			// Check out first connection.
+			_, err = p.checkOut(context.Background())
+			noerr(t, err)
+
+			// Use a canceled context to check out another connection.
+			cancelCtx, cancel := context.WithCancel(context.Background())
+			cancel()
+			_, err = p.checkOut(cancelCtx)
+			assert.NotNilf(t, err, "expected a non-nil error")
+
+			// Assert that error received is WaitQueueTimeoutError with context canceled.
+			assert.IsTypef(t, WaitQueueTimeoutError{}, err, "expected a WaitQueueTimeoutError")
+			if err, ok := err.(WaitQueueTimeoutError); ok {
+				assert.Equalf(t, context.Canceled, err.Unwrap(), "expected wrapped error to be a context.Canceled")
+				assert.Containsf(t, err.Error(), "canceled", `expected error message to contain "canceled"`)
+			}
+
 			p.close(context.Background())
 		})
 	})