Add keepalive option to agent server #154

Avatat · 2020-10-20T11:37:14Z

This is a fix to issue #152.

Sometimes, agent can disconnect without closing connection, and server don't know about it. Disconnected agent is still on the available agents list and server tries to route traffic through it.

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k8s-ci-robot · 2020-10-20T11:37:22Z

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k8s-ci-robot · 2020-10-20T11:37:22Z

Hi @Avatat. Thanks for your PR.

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Avatat · 2020-10-20T13:12:00Z

I signed CLA.

Jefftree · 2020-10-20T14:31:39Z

/ok-to-test

Avatat · 2020-10-20T15:31:12Z

/retest

Avatat · 2020-10-20T15:37:38Z

@Jefftree, should I write a test, which will cover a bug from #152?
To be honest, I have no idea how to do this, where to begin.

cheftako · 2020-10-20T16:32:12Z

cmd/server/main.go

-	grpcServer := grpc.NewServer(serverOption)
+	serverOptions := []grpc.ServerOption {
+		grpc.Creds(credentials.NewTLS(tlsConfig)),
+		grpc.KeepaliveParams(keepalive.ServerParameters{Time: 30 * time.Second}),


This is way too short to be the default. Currently the max K8s cluster size is 15K nodes. For such a cluster you would be sending 500 keep-alive packets per second to each server. I would suggest making the default 1 hour (the default TCP keepalive on the server is 2 hours (so 1/2 that is good) and the default server enforced minimum is 5 minutes). I'm fine with this being a optional command line flag so you can tune this to your needs. I think we are still likely to also want to mark problematic tunnels as unhealthy but having both seems a good idea.

I wonder if we also want to set a keep alive on the agent side.

Adding an optional command line flag is a good idea - I will figure it out.

As I understand, we don't need a keepalive mechanism on the agent side, because we currently check health there, using grpc.ClientConn.GetState.

I believe (I could certainly be wrong) that that GetState is mostly tracking if closed has been called. It is not tracking if we have either a network outage such that traffic doesn't route or that the server has gone away without notifying us. These are the conditions which keepalive is meant to help. https://godoc.org/google.golang.org/grpc#WithKeepaliveParams client side keep alive is almost identical to server side keepalive and they should work well together.

Just going to add that SSH tunnels have a healthCheckPoll time of 1 minute (https://github.com/kubernetes/kubernetes/blob/master/pkg/ssh/ssh.go#L316), so it's possible that we could go lower than 1 hour for the keepalive time.

We can probably address client side keep alive in a separate PR.

I think so, too. ~1 minute keepalive time isn't something bad for performance - remember, that we send keepalive packets only when the channel is inactive for longer than specified time. In a 15K-node cluster, administrators probably will not deploy konnectivity as daemonset, on every node.
I'm currently working on adding a command line option to allow the administrator to tune this parameter.

After I complete this PR, I would like to try to add keepalive to the agent and then create a new PR :)

@cheftako, @Jefftree, I've just added a --keepalive-time command-line option to the server code and Kubernetes example.

cmd/server/main.go

This is a fix to issue #152. Sometimes, agent can disconnect without closing connection, and server don't know about it. Disconnected agent is still on the available agents list and server tries to route traffic through it.

cheftako · 2020-10-21T15:50:47Z

/lgtm
/approve

k8s-ci-robot · 2020-10-21T15:50:59Z

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Avatat, cheftako

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k8s-ci-robot added the cncf-cla: no Indicates the PR's author has not signed the CNCF CLA. label Oct 20, 2020

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k8s-ci-robot requested review from Jefftree and Sh4d1 October 20, 2020 11:37

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Avatat mentioned this pull request Oct 20, 2020

Server tries to route traffic through "hard" disconnected agents #152

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cmd/server/main.go Outdated Show resolved Hide resolved

Add keepalive option to agent server

b653688

This is a fix to issue #152. Sometimes, agent can disconnect without closing connection, and server don't know about it. Disconnected agent is still on the available agents list and server tries to route traffic through it.

k8s-ci-robot assigned cheftako Oct 21, 2020

k8s-ci-robot added the lgtm "Looks good to me", indicates that a PR is ready to be merged. label Oct 21, 2020

k8s-ci-robot added the approved Indicates a PR has been approved by an approver from all required OWNERS files. label Oct 21, 2020

k8s-ci-robot merged commit 806811f into kubernetes-sigs:master Oct 21, 2020

Avatat deleted the server-keepalive branch October 21, 2020 16:43

Jefftree mentioned this pull request Nov 9, 2020

Bump network proxy to v0.0.14 kubernetes/kubernetes#96389

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Add keepalive option to agent server #154

Add keepalive option to agent server #154

Avatat commented Oct 20, 2020

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cheftako Oct 20, 2020 •

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Add keepalive option to agent server #154

Add keepalive option to agent server #154

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