cbt-aggapi

README

CBT Aggregated API Server

This repository contains an aggregated API server prototype that can serve the CSI changed block tracking API.

The primary goal is to explore options to implement an in-cluster API endpoint which can be used to retrieve a long list of changed block entries (in the order of hundreds of MiB), without burdening the Kubernetes API server and etcd during data retrieval.

This prototype explores:

• The implementation of a non-etcd custom storage that supports the Kubernetes rest.Connecter interface
• The implementation of a custom Option that converts url.Values to a runtime.Object

The custom REST storage has a GET handler which returns a collection of changed block entries, if the fetchcbd query parameter is specified.

Essentially, the default API endpoint returns a VolumeSnapshotDelta custom resource:

curl "http://127.0.0.1:8001/apis/cbt.storage.k8s.io/v1alpha1/namespaces/default/volumesnapshotdeltas/test-delta" | jq .
{
  "kind": "VolumeSnapshotDelta",
  "apiVersion": "cbt.storage.k8s.io/v1alpha1",
  "metadata": {
    "name": "test-delta",
    "namespace": "default",
    "creationTimestamp": null
  },
  "spec": {
    "baseVolumeSnapshotName": "base",
    "targetVolumeSnapshotName": "target",
    "mode": "block"
  },
}

Appending the API endpoint with the fetchcbd=true query parameter will append the list of changed block entries to the response:

curl "http://127.0.0.1:8001/apis/cbt.storage.k8s.io/v1alpha1/namespaces/default/volumesnapshotdeltas/test-delta?fetchcbd-true&limit=256&offset=0" | jq .
{
  "kind": "VolumeSnapshotDelta",
  "apiVersion": "cbt.storage.k8s.io/v1alpha1",
  "metadata": {
    "name": "test-delta",
    "namespace": "default",
    "creationTimestamp": null
  },
  "spec": {
    "baseVolumeSnapshotName": "base",
    "targetVolumeSnapshotName": "target",
    "mode": "block"
  },
  "status": {
    "ChangedBlockDeltas": [
      {
        "offset": 0,
        "blockSizeBytes": 524288,
        "dataToken": {
          "token": "ieEEQ9Bj7E6XR",
          "issuanceTime": "2022-07-13T03:19:30Z",
          "ttl": "3h0m0s"
        }
      },
      {
        "offset": 1,
        "blockSizeBytes": 524288,
        "dataToken": {
          "token": "widvSdPYZCyLB",
          "issuanceTime": "2022-07-13T03:19:30Z",
          "ttl": "3h0m0s"
        }
      },
      {
        "offset": 2,
        "blockSizeBytes": 524288,
        "dataToken": {
          "token": "VtSebH83xYzvB",
          "issuanceTime": "2022-07-13T03:19:30Z",
          "ttl": "3h0m0s"
        }
      }
    ]
  }
}

Most of the setup code of the aggregated API server is generated using the apiserver-builder tool.

Quick Start

Setup and connect to a Kubernetes cluster.

Create the csi-cbt namespace:

kubectl create ns csi-cbt

Deploy etcd, the aggregated API server and the mock components:

make deploy

The Docker images are hosted on public repositories at quay.io/isim.

Confirm that all the pods are running:

kubectl -n csi-cbt get po

NAME                             READY   STATUS    RESTARTS   AGE
etcd-0                           1/1     Running   0          103m
cbt-aggapi-77888d6579-cwz8n      1/1     Running   0          102m
sample-driver-6c8dd6d957-xks74   2/2     Running   0          2m40s
backup-client-6696b88659-dcc4m   1/1     Running   0          108s

Create a VolumeSnapshotDelta resource:

cat<<EOF | kubectl create -f -
apiVersion: cbt.storage.k8s.io/v1alpha1
kind: VolumeSnapshotDelta
metadata:
  name: test-delta
  namespace: default
spec:
  baseVolumeSnapshotName: vs-00
  targetVolumeSnapshotName: vs-01
  mode: block
EOF

Use kubectl to GET the resources:

kubectl get volumesnapshotdelta test-delta -oyaml

apiVersion: cbt.storage.k8s.io/v1alpha1
kind: VolumeSnapshotDelta
metadata:
  creationTimestamp: null
  name: test-delta
  namespace: default
spec:
  baseVolumeSnapshotName: base
  mode: block
  targetVolumeSnapshotName: target
status: {}

Use the kubectl proxy to start a proxy between localhost and cluster:

kubectl proxy &

Get the changed block entries of the resource:

curl -k "http://127.0.0.1:8001/apis/cbt.storage.k8s.io/v1alpha1/namespaces/default/volumesnapshotdeltas/test-delta?fetchcbd=true&limit=256&offset=0"

{
  "kind": "VolumeSnapshotDelta",
  "apiVersion": "cbt.storage.k8s.io/v1alpha1",
  "metadata": {
    "name": "test-delta",
    "namespace": "default",
    "creationTimestamp": null
  },
  "spec": {
    "baseVolumeSnapshotName": "base",
    "targetVolumeSnapshotName": "target",
    "mode": "block"
  },
  "status": {
    "changedBlockDeltas": [
      {
        "offset": 0,
        "blockSizeBytes": 524288,
        "dataToken": {
          "token": "ieEEQ9Bj7E6XR",
          "issuanceTime": "2022-07-13T03:30:46Z",
          "ttl": "3h0m0s"
        }
      },
      {
        "offset": 1,
        "blockSizeBytes": 524288,
        "dataToken": {
          "token": "widvSdPYZCyLB",
          "issuanceTime": "2022-07-13T03:30:46Z",
          "ttl": "3h0m0s"
        }
      },
      {
        "offset": 2,
        "blockSizeBytes": 524288,
        "dataToken": {
          "token": "VtSebH83xYzvB",
          "issuanceTime": "2022-07-13T03:30:46Z",
          "ttl": "3h0m0s"
        }
      }
    ]
  }
}

The backup-client component can also issue requests to the cbt-aggapi server.

Set up port-forward to the backup-client so that it's accessible at your localhost:

kubectl -n csi-cbt port-forward svc/backup-client 8080

Send requests to the backup-client to emulate calls to the cbt-aggapi server:

curl localhost:8080/apis/test-delta-02

Fetch all the changed block entries too:

curl localhost:8080/apis/test-delta-02/extended

To remove all the prototype components:

make clean

Development

Install the apiserver-builder tool following the instructions here. The apiserver-boot tool requires the code to be checked out into the local $GOPATH i.e. github.com/ihcsim/cbt-aggapi.

To run the tests:

go test ./...

To work with the Docker images, first define the repository URL and tag for your images:

export IMAGE_REPO_AGGAPI=<your_agg_apiserver_image_repo>
export IMAGE_TAG_AGGAPI=<your_agg_apiserver_image_tag>
export IMAGE_REPO_GRPC=<your_agg_apiserver_image_repo>
export IMAGE_TAG_GRPC=<your_agg_apiserver_image_tag>

Then use these make targets to build and push the images:

make image

make push

Re-generate Code and YAML

The Kubernetes YAML manifests are found in the yaml folder. To re-generate them:

make yaml

This will output all the manifests into the yaml-generated folder. Move what is needed into the yaml folder.

License

Apache License 2.0, see LICENSE.