daemon: add grpc.WithBlock option

WithBlock makes sure that the following containerd request is reliable.

In one edge case with high load pressure, kernel kills dockerd, containerd
and containerd-shims caused by OOM. When both dockerd and containerd
restart, but containerd will take time to recover all the existing
containers. Before containerd serving, dockerd will failed with gRPC
error. That bad thing is that restore action will still ignore the
any non-NotFound errors and returns running state for
already stopped container. It is unexpected behavior. And
we need to restart dockerd to make sure that anything is OK.

It is painful. Add WithBlock can prevent the edge case. And
n common case, the containerd will be serving in shortly.
It is not harm to add WithBlock for containerd connection.

Signed-off-by: Wei Fu <fuweid89@gmail.com>

daemon/daemon.go

@@ -887,6 +887,24 @@ func NewDaemon(ctx context.Context, config *config.Config, pluginStore *plugin.S
  registerMetricsPluginCallback(d.PluginStore, metricsSockPath)
 
  gopts := []grpc.DialOption{
+ // WithBlock makes sure that the following containerd request
+ // is reliable.
+ //
+ // NOTE: In one edge case with high load pressure, kernel kills
+ // dockerd, containerd and containerd-shims caused by OOM.
+ // When both dockerd and containerd restart, but containerd
+ // will take time to recover all the existing containers. Before
+ // containerd serving, dockerd will failed with gRPC error.
+ // That bad thing is that restore action will still ignore the
+ // any non-NotFound errors and returns running state for
+ // already stopped container. It is unexpected behavior. And
+ // we need to restart dockerd to make sure that anything is OK.
+ //
+ // It is painful. Add WithBlock can prevent the edge case. And
+ // n common case, the containerd will be serving in shortly.
+ // It is not harm to add WithBlock for containerd connection.
+ grpc.WithBlock(),
+
  grpc.WithInsecure(),
  grpc.WithBackoffMaxDelay(3 * time.Second),
  grpc.WithDialer(dialer.Dialer),