database/sql: add Pinger interface to driver Conn

Change-Id: If6eb3a7c9ad48a517e584567b1003479c1df6cca
Reviewed-on: https://go-review.googlesource.com/32136
Reviewed-by: Daniel Theophanes <kardianos@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

1 files changed, 18 insertions, 6 deletions

diff --git a/src/database/sql/sql.go b/src/database/sql/sql.go
index 3cef4b6404..6d2dcb8c73 100644
--- a/src/database/sql/sql.go
+++ b/src/database/sql/sql.go
@@ -553,15 +553,27 @@ func Open(driverName, dataSourceName string) (*DB, error) {
 // PingContext verifies a connection to the database is still alive,
 // establishing a connection if necessary.
 func (db *DB) PingContext(ctx context.Context) error {
-	// TODO(bradfitz): give drivers an optional hook to implement
-	// this in a more efficient or more reliable way, if they
-	// have one.
-	dc, err := db.conn(ctx, cachedOrNewConn)
+	var dc *driverConn
+	var err error
+
+	for i := 0; i < maxBadConnRetries; i++ {
+		dc, err = db.conn(ctx, cachedOrNewConn)
+		if err != driver.ErrBadConn {
+			break
+		}
+	}
+	if err == driver.ErrBadConn {
+		dc, err = db.conn(ctx, alwaysNewConn)
+	}
 	if err != nil {
 		return err
 	}
-	db.putConn(dc, nil)
-	return nil
+
+	if pinger, ok := dc.ci.(driver.Pinger); ok {
+		err = pinger.Ping(ctx)
+	}
+	db.putConn(dc, err)
+	return err
 }
 
 // Ping verifies a connection to the database is still alive,