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by JoosToopit 734 days ago
My process connects to, say, Postgres. What's going to happen to that connection upon restore?

Does crik guarantee the order of events (saving a checkpoint should be followed by killing the old process/pod, which should be followed by a restoration - the order of these 3 events is strict) and given that criu can checkpoint and restore sockets state correctly - how does that work for kubernetes? The new pod will have a different IP.
2 comments
monus 734 days ago
TCP connections are identified with source IP:port and target IP:port tuples. When a new pod is created, it gets a new IP so there is not much way to restore the TCP connections. So crik drops all TCP connections and lets the application handle the reconnection logic. There are some CNIs that can give a static IP to pod, but that’s rather unorthodox in k8s.
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zamalek 734 days ago
Right, and this shouldn't be a big issue for [competent] cloud-native software: it's a transient fault. If your software can't recover from transient faults then this is the wrong ecosystem to be considering.
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rmetzler 734 days ago
> The new pod will have a different IP.

Usually clients would connect to a Kubernetes svc to not have the problem with changing IPs. Even for just a single pod I would do that.

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mathfailure 734 days ago
The app in the pod is the client (of a DBMS server). The client's IP gets changed. A service in k8s is a network node with an address, but it is used for inbound connections, outbound connections (like from the app to a DBMS server, which may be outside of k8s cluster) usually do not use services (as it gives no benefits).
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