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Somtochi Onyekwere
2020-08-26 07:13:54 +01:00
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content/en/blog/_posts/2020-08-25-gsoc‘20 -building-operators-for-cluster-addons.md
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# Introduction # Introduction
Google Summer of Code is a global program that is geared towards introducing students to open source. Students are matched with open-source organizations to work with them for three months during the summer. [Google Summer of Code](https://summerofcode.withgoogle.com/) is a global program that is geared towards introducing students to open source. Students are matched with open-source organizations to work with them for three months during the summer.
My name is Somtochi Onyekwere from the Federal University of Technology, Owerri(Nigeria) and this year, I was opportune to be selected as one of the interns to work with Kubernetes(under the CNCF organization) and this led to an amazing summer spent learning, contributing and interacting with the community. My name is Somtochi Onyekwere from the Federal University of Technology, Owerri (Nigeria) and this year, I given the opportunity to work with Kubernetes (under the CNCF organization) and this led to an amazing summer spent learning, contributing and interacting with the community.
Specifically, I worked the [Cluster Addons: Package all things!](https://github.com/cncf/mentoring/blob/master/summerofcode/README.md#cluster-addons-package-all-the-things) Project. The project focused on building operators for better management of various cluster addons, extending the tooling for building these operators and making the creation of these operators a smooth process. Specifically, I worked on the [Cluster Addons: Package all things!](https://github.com/cncf/mentoring/blob/master/summerofcode/README.md#cluster-addons-package-all-the-things) project. The project focused on building operators for better management of various cluster addons, extending the tooling for building these operators and making the creation of these operators a smooth process.
# Background # Background
Kubernetes have progressed greatly in the past few years with a flourishing community and a large number of contributors. The codebase has definitely moved away from the monolith structure where all the code resided in the [k/k](https://github.com/kubernetes/kubernetes) repository to being split into multiple sub-projects. Part of the focus of Cluster-addons is to make all these sub-projects work together in an easy to assemble, self-monitoring, self-healing and Kubernetes-native way. It enables them to work seamlessly without human intervention. Kubernetes has progressed greatly in the past few years with a flourishing community and a large number of contributors. The codebase has definitely moved away from the monolith structure where all the code resided in the [kubernetes/kubernetes](https://github.com/kubernetes/kubernetes) repository to being split into multiple sub-projects. Part of the focus of Cluster-addons is to make all these sub-projects work together in an easy to assemble, self-monitoring, self-healing and Kubernetes-native way. It enables them to work seamlessly without human intervention.
The community is exploring the use of operators as a mechanism to monitor various resources in the cluster and properly manage these resources. In addition to this, it provides self-healing and it is a kubernetes-native pattern that can encode how best these addons work and manage them properly. The community is exploring the use of operators as a mechanism to monitor various resources in the cluster and properly manage these resources. In addition to this, it provides self-healing and it is a kubernetes-native pattern that can encode how best these addons work and manage them properly.
What are cluster addons? Cluster addons are a collection of resources(like Services and deployment) that are used to give a Kubernetes cluster additional functionalities. They range from things as simple as the Kubernetes dashboards(for visualization) to more complex ones like Calico(for Networking). These addons are essential to different applications running in the cluster and the cluster itself. The addon operator provides a nicer way of managing these addons and understanding the health and status of the various resources that comprise the addon. What are cluster addons? Cluster addons are a collection of resources (like Services and deployment) that are used to give a Kubernetes cluster additional functionalities. They range from things as simple as the Kubernetes dashboards (for visualization) to more complex ones like Calico (for networking). These addons are essential to different applications running in the cluster and the cluster itself. The addon operator provides a nicer way of managing these addons and understanding the health and status of the various resources that comprise the addon.
Operators, on the other hand, are custom controllers and custom resource definitions that encode application-specific knowledge and are used for managing complex stateful applications. It is a widely accepted pattern. Managing addons via operators, with these operators encoding knowledge of how best the addons work, introduces a lot of advantages while setting standards that will be easy to follow and scale. Operators, on the other hand, are custom controllers and custom resource definitions that encode application-specific knowledge and are used for managing complex stateful applications. It is a widely accepted pattern. Managing addons via operators, with these operators encoding knowledge of how best the addons work, introduces a lot of advantages while setting standards that will be easy to follow and scale.
@@ -45,14 +45,14 @@ The reconciliation loop that ensures that the desired state matches the actual s
One of the operators that I worked on is a generic controller that could manage more than one cluster addon that did not require extra configuration. To do this, the operator couldn’t use a particular type and needed the kubebuilder-declarative-repo to support using the [unstructured.Unstructured](https://godoc.org/k8s.io/apimachinery/pkg/apis/meta/v1/unstructured#Unstructured) type. There were various functions in the kubebuilder-declarative-pattern that couldn’t handle this type and return an error if the object passed in was not of type `addonsv1alpha1.CommonObject`. The functions were modified to handle both unstructured.Unstructured and addonsv1alpha.CommonObject. One of the operators that I worked on is a generic controller that could manage more than one cluster addon that did not require extra configuration. To do this, the operator couldn’t use a particular type and needed the kubebuilder-declarative-repo to support using the [unstructured.Unstructured](https://godoc.org/k8s.io/apimachinery/pkg/apis/meta/v1/unstructured#Unstructured) type. There were various functions in the kubebuilder-declarative-pattern that couldn’t handle this type and return an error if the object passed in was not of type `addonsv1alpha1.CommonObject`. The functions were modified to handle both unstructured.Unstructured and addonsv1alpha.CommonObject.
# Tools and CLI programs # Tools and CLI programs
There were also some command-line programs I wrote that could be used to make working with addon operators easier. Most of them have uses outside the addon operators as they try to solve a specific problem that could surface anywhere while working with Kubernetes. I encourage you to check them out when you have the chance! There were also some command-line programs I wrote that could be used to make working with addon operators easier. Most of them have uses outside the addon operators as they try to solve a specific problem that could surface anywhere while working with Kubernetes. I encourage you to [check them out](https://github.com/kubernetes-sigs/cluster-addons/tree/master/tools) when you have the chance!
## RBAC generator ## [RBAC generator](https://github.com/kubernetes-sigs/cluster-addons/tree/master/tools/rbac-gen)
One of the biggest concerns with the operator was RBAC. You had to manually look through the manifest and add the RBAC rule for each resource as it needs to have RBAC permissions to create, get, update and delete the resources in the manifest when running in-cluster. Building the RBAC generator automated the process of writing the RBAC roles and role bindings. The function of the RBAC generator is simple. It accepts the file name of the manifest as a flag. Then, it parses the manifest and gets the API group and resource name of the resources and adds it to a role. It outputs the role and role binding to stdout or a file if the `--out` flag is parsed. One of the biggest concerns with the operator was RBAC. You had to manually look through the manifest and add the RBAC rule for each resource as it needs to have RBAC permissions to create, get, update and delete the resources in the manifest when running in-cluster. Building the RBAC generator automated the process of writing the RBAC roles and role bindings. The function of the RBAC generator is simple. It accepts the file name of the manifest as a flag. Then, it parses the manifest and gets the API group and resource name of the resources and adds it to a role. It outputs the role and role binding to stdout or a file if the `--out` flag is parsed.
Additionally, the tool enables you to split the RBAC by separating the cluster roles in the manifest. This lessened the security concern of an operator being over-privileged as it needed to have all the permissions that the clusterrole has. If you want to apply the clusterrole yourself and not give the operator these permissions, you can pass in a `--supervisory` boolean flag so that the generator does not add these permissions to the role. The CLI program resides [here](https://github.com/kubernetes-sigs/cluster-addons/blob/master/tools/rbac-gen/main.go). Additionally, the tool enables you to split the RBAC by separating the cluster roles in the manifest. This lessened the security concern of an operator being over-privileged as it needed to have all the permissions that the clusterrole has. If you want to apply the clusterrole yourself and not give the operator these permissions, you can pass in a `--supervisory` boolean flag so that the generator does not add these permissions to the role. The CLI program resides [here](https://github.com/kubernetes-sigs/cluster-addons/blob/master/tools/rbac-gen/main.go).
## Kubectl Ownerref ## [Kubectl Ownerref](https://github.com/kubernetes-sigs/cluster-addons/tree/master/tools/kubectl-ownerref)
It is hard to find out at a glance which objects were created by an addon custom resource, this kubectl plugin alleviates that pain by displaying all the objects in the cluster that a resource has ownerrefs on. You simply pass the kind and the name of the resource as arguments to the program and it checks the cluster for the objects and gives the kind, name, the namespace of such object. It could be useful to get a general overview of all the objects that the controller is reconciling by passing in the name and kind of custom resource. It is hard to find out at a glance which objects were created by an addon custom resource, this kubectl plugin alleviates that pain by displaying all the objects in the cluster that a resource has ownerrefs on. You simply pass the kind and the name of the resource as arguments to the program and it checks the cluster for the objects and gives the kind, name, the namespace of such object. It could be useful to get a general overview of all the objects that the controller is reconciling by passing in the name and kind of custom resource.
# Addon Operators # Addon Operators
@@ -63,7 +63,7 @@ The generic controller is a general controller that can be shared between addons
The process is as follows The process is as follows
- Create the Generic CRD - Create the Generic CRD
- Generate all the manifest needed with the `generic-addon` tool found here (here)[https://github.com/kubernetes-sigs/cluster-addons/blob/master/tools/generic-addon/README.md]. - Generate all the manifest needed with the `generic-addon` tool found [here](https://github.com/kubernetes-sigs/cluster-addons/blob/master/tools/generic-addon/README.md).
This tool creates This tool creates
1. The CRD for your addon 1. The CRD for your addon