conn

type Connector interface {
	// Open opens a sql.Conn from the pool. It returns the error from sql.Conn,
	// if any. The caller should pass the error to Error to return a high-level
	// error exported by this package.
	Open(context.Context) (*sql.Conn, error)

	// Close closes a sql.Conn by calling its Close method. The caller should call
	// this method instead of calling conn.Close directly. Do not call both, but
	// one or the other must be called to return the connection to the pool. It
	// returns the error from conn.Close, if any.
	Close(*sql.Conn) error

	// Error returns true if the given error indicates the connection was lost,
	// else it returns false. If true, the caller should wait and retry the
	// operation. The driver will attempt to reconnect, but it usually takes
	// one or two attempts after the first error before the driver reestablishes
	// the connection. This is a driver implementation detail that cannot be
	// changed by the caller.
	//
	// The returned error can be different than the given error. Certain low-level
	// MySQL errors are returned as high-level errors exported by this package,
	// like ErrQueryKilled and ErrReadOnly. These high-level errors are common
	// and usually require special handling or retries by the caller. The caller
	// should check for and handle these high-level errors. Other errors are
	// probably not recoverable and should be logged and reported as an internal
	// error or bug.
	//
	// If the given error is not a MySQL error or nil, the method does nothing
	// and returns false and the given error.
	//
	// The caller should always call this method with any error from any code
	// that used a sql.Conn. See packages docs for the canonical workflow.
	Error(error) (bool, error)
}

type Pool struct {
	// contains filtered or unexported fields
}

type Stats struct {
	*sync.Mutex
	Ts        int64 // Unix timestamp when stats were returned
	Open      int   // sql.DBStats.OpenConnections, not always accurate (gauge)
	OpenCalls int   // All calls to Open (counter)
	Opened    uint  // Successful calls to Open (counter)
	Closed    uint  // All calls to close (counter)
	Timeout   uint  // Timeouts during calls to Open (counter)
	Lost      uint  // Lost connections (counter)
	Down      uint  // ErrConnCannotConnect errors (counter)
}