util/treecache/treecache.go
func (zl ZookeeperLogger) Printf(s string, i ...interface{}) {
	level.Info(zl.logger).Log("msg", fmt.Sprintf(s, i...))
}
func (zl ZookeeperLogger) Printf(s string, i ...interface{}) {
	level.Info(zl.logger).Log("msg", fmt.Sprintf(s, i...))
}
// Printf implements zk.Logger.