daemon: add grpc.WithBlock option

[fuweid]

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

[fuweid]

ping @thaJeztah and @AkihiroSuda

[thaJeztah]

@dmcgowan @cpuguy83 ptal 🤗

[dmcgowan]

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.

Isn't this just Docker mishandling the errors? My understanding is WithBlock was actually changing the underlying connection to not use a pool and wasn't handling reconnects after that.

edit: my understanding may have been based on a much older version of grpc, I cannot prove this based on the currently vendored version.

[fuweid]

@dmcgowan For now, WithBlock just blocks dial call until the connection is ready. And it will not impact the following reconnect. I test in local and dockerd will reconnect if containerd is down temporarily.

Isn't this just Docker mishandling the errors?

Basically, Yes. Checkout the following code and it seems that dockerd need to introduce new state for container if failed to restore the running container. But if we add WithBlock, it can reduce unexpected behaviors caused by connection error.

// daemon/daemon.go
alive, _, process, err = daemon.containerd.Restore(context.Background(), c.ID, c.InitializeStdio)
if err != nil && !errdefs.IsNotFound(err) {
     logrus.Errorf("Failed to restore container %s with containerd: %s", c.ID, err)
     return
}

[fuweid]

any update?

[thaJeztah]

@dmcgowan PTAL

[AkihiroSuda]

@cpuguy83 PTAL?

[fuweid]

any updates?

[cpuguy83]

LGTM

Thanks for your patience!

[cpuguy83]

Added cherry-pick since this seems like something we'd want on 19.03

@fuweid Did you want to open a backport?

[fuweid]

Added cherry-pick since this seems like something we'd want on 19.03

@fuweid Did you want to open a backport?

@cpuguy83 Will do that! Thanks for the review.