Add experimental CRI API for checkpoint/restore #97689

adrianreber · 2021-01-04T17:02:39Z

What type of PR is this?

/kind feature
/kind api-change

What this PR does / why we need it:

This PR contains the first two commits of #97194. I created this PR to make it easier to review the CRI API changes without all the changes for the actual feature implementation in #97194.

I also want to make it easier to continue the discussion in kubernetes/enhancements#1990

This introduces a new, experimental CRI API.

Which issue(s) this PR fixes:
It partly fixes #3949 but it is just a step towards solving #3949 . The next step would be #97194 .

Special notes for your reviewer:
Just two commits split out of #97194 for easier review.

Does this PR introduce a user-facing change?:

NONE

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:
kubernetes/enhancements#1990

k8s-ci-robot · 2021-01-04T17:02:47Z

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k8s-ci-robot · 2021-01-04T17:02:48Z

Hi @adrianreber. Thanks for your PR.

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fejta-bot · 2021-01-04T17:32:50Z

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dims · 2021-01-04T18:58:17Z

/assign @derekwaynecarr @mrunalp

Derek, Mrunal, how does this fit into the CRI API stuff in progress?

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/check-cla

krmayankk · 2021-01-05T08:46:32Z

staging/src/k8s.io/cri-api/pkg/apis/runtime/v1alpha2/api.proto

+    // CheckpointContainer checkpoints a container
+    rpc CheckpointContainer(CheckpointContainerRequest) returns (CheckpointContainerResponse) {}
+    // RestoreContainer restores a container
+    rpc RestoreContainer(RestoreContainerRequest) returns (RestoreContainerResponse) {}


does this apply to all types of containers ? e.g. init and sidecars flagged as well?

does this apply to all types of containers ? e.g. init and sidecars flagged as well?

In my drain --checkpoint implementation (#97194) I am ignoring containers in the 'kube-system' namespace. As long as no raw sockets are used CRIU could checkpoint most processes and containers, but it does not seem useful to checkpoint containers in the 'kube-system' namespace for now.

Checkpointing a Pod in CRI-O also does not checkpoint the pause container, only necessary metadata is written to the checkpoint archive and upon restore a new pause container is created which uses the metadata to provide the same environment for the other restored containers.

Thanks @adrianreber , i was asking about https://kubernetes.io/docs/concepts/workloads/pods/init-containers/
Also does it make sense for the CRI to know about kubernetes namespace kube-system at the CRI level ? I believe that logic should be built into kubelet and not into CRI

i was asking about https://kubernetes.io/docs/concepts/workloads/pods/init-containers/

This was briefly discussed in the corresponding KEP and one idea was to not enable checkpointing before init containers have finished running.

Also does it make sense for the CRI to know about kubernetes namespace kube-system at the CRI level ? I believe that logic should be built into kubelet and not into CRI

Currently it happens in kubectl. Only containers which are not in the 'kube-system' namespace are checkpointed.

krmayankk · 2021-01-05T09:03:30Z

staging/src/k8s.io/cri-api/pkg/apis/runtime/v1alpha2/api.proto

+    // Keep temporary files. Like log files. Helpful for debugging.
+    bool keep = 1;
+    // Checkpoint/Restore the container with established TCP connections.
+    bool tcp_established = 2;


is it possible to checkpoint and restore with established tcp connections ? How does that work ?

is it possible to checkpoint and restore with established tcp connections ?

Yes it is possible to checkpoint and restore established TCP connections. On the lower levels, checkpointing single processes or containers using runc/Podman it makes more sense when talking about the TCP connection from an outside client to the process or container. The restored process or container needs to have access to the same IP or the restore will fail.

In the Kubernetes context, especially for the current drain --checkpoint implementation, it might seem less useful for connections to external clients. It is, however, important to have the possibility to checkpoint and restore established TCP connections for containers and Pods which have open TCP connection between each other.

How does that work ?

Please have a look at how CRIU does that: https://criu.org/TCP_connection

riteshnaik · 2021-01-08T20:27:00Z

staging/src/k8s.io/cri-api/pkg/apis/runtime/v1alpha2/api.pb.go

@@ -6964,6 +6964,395 @@ func (m *ReopenContainerLogResponse) XXX_DiscardUnknown() {

 var xxx_messageInfo_ReopenContainerLogResponse proto.InternalMessageInfo

+// Common options used for checkpointing and restoring.
+type CheckpointRestoreOptions struct {


How about adding an image directory option for a custom checkpoint storage directory that checkpoint and restore could use to save the checkpoint and restore from the checkpoint respectively?

See the archive option. A container checkpoint is much more than just the result of running CRIU. Then a directory would make sense. To make life easier for users I put everything in a tar archive in Podman. The CRIU checkpoint, the changes to the container file system and metadata (like name, IP address, ID and much more). Without those additional information it is difficult to restore a container as it was before without requiring a lot of manual steps from the user during restore. The archive contains everything. Please also see me CRI-O implementation where I either put all container information as described above in a tar archive or even a complete Pod checkpoint containing all information about a Pod to be restored.

Ah...I missed the archive option here. Thanks for clarifying and explaining the details behind the archive option. I started by looking to check if there is an option to restore multiple containers from the same checkpoint and seems like there is. Restore has to be just pointed to the archive using the import option and given a new name via the name option.
I did go through the Podman implementation and as I mentioned earlier it did answer a lot of my questions. I haven't had the chance to go over the CRI-O implementation yet and will definitely go over it to learn more on a complete Pod checkpoint workflow.

riteshnaik · 2021-01-08T20:28:14Z

staging/src/k8s.io/cri-api/pkg/apis/runtime/v1alpha2/api.pb.go

@@ -6964,6 +6964,395 @@ func (m *ReopenContainerLogResponse) XXX_DiscardUnknown() {

 var xxx_messageInfo_ReopenContainerLogResponse proto.InternalMessageInfo

+// Common options used for checkpointing and restoring.


Wondering what's the plan for adding more options in the future? Is this the exhaustive list or plan is to start with some basic options and to add more based on the use cases? Are these options based on options that are available for criu?

The list of options is based on my work on Podman. All the features I implemented there I added here as they seem to be the most interesting to begin with. It also depends on what runc/crun can do. One of the things runc can currently do which is not represented here is pre-copy and post-copy migration. Which is nice to have in the future but I do not think it is important to think about it now.

Going through your work on adding checkpoint/restore support for Podman helped me put things in perspective and answered my questions. Thanks!

ehashman

/hold
since this is a POC PR for a KEP which hasn't been approved

/ok-to-test

k8s-ci-robot · 2021-02-25T09:06:12Z

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: adrianreber
To complete the pull request process, please assign derekwaynecarr, liggitt after the PR has been reviewed.
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adrianreber · 2021-02-25T09:14:00Z

/test pull-kubernetes-node-e2e

adrianreber · 2021-02-25T09:40:22Z

/test pull-kubernetes-node-e2e

adrianreber · 2021-02-25T09:41:14Z

/test pull-kubernetes-bazel-test

adrianreber · 2021-02-25T09:47:56Z

/test pull-kubernetes-node-e2e

First user of this experimental CRI API is checkpoint/restore. The idea behind this experimental API is that CRI implementations do not have to implement this but it makes it possible to easily test new features which require additions to the CRI API. Signed-off-by: Adrian Reber <areber@redhat.com>

Signed-off-by: Adrian Reber <areber@redhat.com>

adrianreber · 2021-02-25T10:38:41Z

/test pull-kubernetes-node-e2e
/test pull-kubernetes-e2e-kind

k8s-ci-robot · 2021-02-25T10:42:47Z

@adrianreber: The following tests failed, say /retest to rerun all failed tests:

Test name	Commit	Details	Rerun command
pull-kubernetes-e2e-azure-file	4b922f8950c497663e3abfa7f943ca2160373a10	link	`/test pull-kubernetes-e2e-azure-file`
pull-kubernetes-e2e-azure-disk	4b922f8950c497663e3abfa7f943ca2160373a10	link	`/test pull-kubernetes-e2e-azure-disk`
pull-kubernetes-e2e-azure-disk-windows	4b922f8950c497663e3abfa7f943ca2160373a10	link	`/test pull-kubernetes-e2e-azure-disk-windows`
pull-kubernetes-e2e-azure-file-windows	4b922f8950c497663e3abfa7f943ca2160373a10	link	`/test pull-kubernetes-e2e-azure-file-windows`
pull-kubernetes-e2e-aks-engine-azure	4b922f8950c497663e3abfa7f943ca2160373a10	link	`/test pull-kubernetes-e2e-aks-engine-azure`
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pull-kubernetes-e2e-gce-alpha-features	4b922f8950c497663e3abfa7f943ca2160373a10	link	`/test pull-kubernetes-e2e-gce-alpha-features`
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adrianreber · 2021-02-25T12:14:35Z

/test pull-kubernetes-node-e2e

k8s-ci-robot · 2021-04-06T02:12:49Z

@adrianreber: PR needs rebase.

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enj · 2021-04-19T14:14:18Z

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adrianreber mentioned this pull request Jan 4, 2021

[WIP] Add --checkpoint to drain #97194

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Add Forensic Container Checkpointing KEP kubernetes/enhancements#1990

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Question: Support for docker checkpoint on Windows? microsoft/Windows-Containers#88

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adrianreber changed the title ~~Extend CRI API for checkpoint/restore~~ Add experimental CRI API for checkpoint/restore Feb 12, 2021

tfenster mentioned this pull request Feb 17, 2021

Support for checkpoint / restore on Windows as well #99170

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adrianreber force-pushed the 2021-01-04-cri-api branch from f72e9f0 to fe53b12 Compare February 25, 2021 09:05

adrianreber added 2 commits February 25, 2021 09:56

Experimental CRI API make update

a740072

Signed-off-by: Adrian Reber <areber@redhat.com>

adrianreber force-pushed the 2021-01-04-cri-api branch from fe53b12 to a740072 Compare February 25, 2021 09:57

adrianreber mentioned this pull request Mar 25, 2021

Pod man error2 checkpoint-restore/criu#1420

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		@@ -6964,6 +6964,395 @@ func (m *ReopenContainerLogResponse) XXX_DiscardUnknown() {

		var xxx_messageInfo_ReopenContainerLogResponse proto.InternalMessageInfo

		// Common options used for checkpointing and restoring.

Add experimental CRI API for checkpoint/restore #97689

Add experimental CRI API for checkpoint/restore #97689

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