Shulou(Shulou.com)06/02 Report--

First of all, I want to share the mission of SIG, because we use it to guide our work now and in the future. Directly from our charter, SIG's mission is to simplify, develop, and maintain cloud provider integration as an extension or add-on to the Kubernetes cluster. The motivation behind this is twofold: to ensure that Kubernetes remains scalable and cloud neutral (agnostic). The current situation of Cloud providers

In order to get a forward-looking perspective, I think it is very important to re-examine the current state of cloud providers. Today, every core Kubernetes component (except the scheduler and kube-proxy) has a-cloud-provider flag that you can configure to enable a set of features that integrate with the underlying infrastructure provider, the cloud provider. Enabling this integration enables a range of features for the cluster, such as node address and zone discovery, cloud load balancer for services with Type= LoadBalancer, IP address management, and cluster network through the VPC routing table. Today, cloud provider integration can be done in or outside the tree.

In-Tree and Out-of-Tree vendors

The in-tree cloud provider is a vendor program that we developed and released in the main Kubernetes repository. This results in the knowledge and context of each cloud vendor embedded in most Kubernetes components. This enables more native integrations (for example, kubelet) to request information about themselves through metadata services from cloud providers.

In-Tree Cloud Provider Architecture

Off-tree cloud providers are vendors that can be developed, built, and released independently of the Kubernetes core. This requires the deployment of a new component called cloud-controller-manager, which is responsible for running all cloud-specific controllers that previously ran in kube-controller-manager.

Out-of-Tree Cloud provider Architecture

When cloud provider integrations were first developed, they were developed natively (in the tree). We integrate each vendor near the core of Kubernetes and in today's k8s.io/kubernetes overall repository. As Kubernetes becomes more common and more and more infrastructure vendors want native support for Kubernetes, we realize that this model will not expand. Each provider brings a large number of dependencies which increases potential vulnerabilities in the code base and significantly increases the binary size of each component. In addition, more Kubernetes release notes are starting to focus on vendor-specific changes rather than core changes that affect all Kubernetes users.

At the end of 2017, we developed a way for cloud providers to build integrations without adding them to the main Kubernetes tree (outside the tree). This has become a de facto way for new infrastructure vendors in the ecosystem to integrate with Kubernetes. Since then, we have been actively trying to migrate all cloud providers to use out-of-tree architecture, because most clusters still use in-tree cloud providers.

look into the future

Looking ahead, SIG's goal is to remove all existing in-tree cloud providers and switch to an out-of-tree implementation with minimal impact on users. In addition to the core cloud vendor integration mentioned above, there are more cloud integration extension points, such as CSI and mirror credential vendors, that are actively working for v1.15. Reaching this point means that Kubernetes is really neutral with the cloud and has no native integration for any cloud provider. Through this work, we enable each cloud provider to develop and release new versions at its own pace independent of Kubernetes. We now know that this is a huge feat with unique challenges. Migrating a workload is by no means easy, especially if it is an important part of the control plane. In the upcoming release, our SIG gives top priority to providing a secure and easy migration path between in-tree and out-of-tree cloud vendors. If you are interested, I suggest you check out some of our KEP and contact our SIG by joining the mailing list or our Slack channel (# sig-cloud-provider in Kubernetesslack).

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