message: Print delay in switch info
diff: @@ -140,7 +140,11 @@ impl Inner {
  }
  None => {
  // Timeout
  - error!("checked remote server {} connect timeout", sc.config.addr());
  + error!(
  + "checked remote server {} connect timeout, elapsed {} ms",
  + sc.config.addr(),
  + elapsed
  + );
  // NOTE: timeout is still available, but server is too slow
  Ok(elapsed)
  @@ -200,13 +204,13 @@ impl PingBalancer {
  if svr_idx == 0 && !choosen_svr.is_available() {
  // Cannot find any usable servers, use the first one (svr_idx = 0)
  error!(
  - "cannot find any usable servers, picked {} delay {} ms",
  + "cannot find any usable servers, picked {} (delay: {} ms)",
  choosen_svr.config.addr(),
  choosen_svr.delay()
  );
  } else {
  debug!(
  - "chosen the best server {} delay {} ms",
  + "chosen the best server {} (delay: {} ms)",
  choosen_svr.config.addr(),
  choosen_svr.delay()
  );
  @@ -214,9 +218,11 @@ impl PingBalancer {
  if inner.best_idx() != svr_idx {
  info!(
  - "switched server from {} to {}",
  + "switched server from {} (delay: {} ms) to {} (delay: {} ms)",
  inner.best_server().config.addr(),
  - choosen_svr.config.addr()
  + inner.best_server().delay(),
  + choosen_svr.config.addr(),
  + choosen_svr.delay(),
  );
  }
  