lens/docs/extensions/guides/renderer-extension.md

Renderer Extension

The renderer extension api is the interface to Lens' renderer process (Lens runs in main and renderer processes). It allows you to access, configure, and customize Lens data, add custom Lens UI elements, and generally run custom code in Lens' renderer process. The custom Lens UI elements that can be added include global pages, cluster pages, cluster features, app preferences, status bar items, KubeObject menu items, and KubeObject details items. These UI elements are based on React components.

LensRendererExtension Class

To create a renderer extension simply extend the LensRendererExtension class:

import { LensRendererExtension } from "@k8slens/extensions";

export default class ExampleExtensionMain extends LensRendererExtension {
  onActivate() {
    console.log('custom renderer process extension code started');
  }

  onDeactivate() {
    console.log('custom renderer process extension de-activated');
  }
}

There are two methods that you can override to facilitate running your custom code. onActivate() is called when your extension has been successfully enabled. By overriding onActivate() you can initiate your custom code. onDeactivate() is called when the extension is disabled (typically from the Lens Extensions Page) and when overridden gives you a chance to clean up after your extension, if necessary. The example above simply logs messages when the extension is enabled and disabled.

clusterPages

Cluster pages appear as part of the cluster dashboard. They are accessible from the side bar, and are shown in the list after Custom Resources. It is conventional to use a cluster page to show information or provide functionality pertaining to the active cluster, along with custom data and functionality your extension may have. However, it is not limited to the active cluster. Your extension can gain access to the Kubernetes resources in the active cluster in a straightforward manner using the clusterStore.

The following example adds a cluster page definition to a LensRendererExtension subclass:

import { LensRendererExtension } from "@k8slens/extensions";
import { ExampleIcon, ExamplePage } from "./page"
import React from "react"

export default class ExampleExtension extends LensRendererExtension {
  clusterPages = [
    {
      path: "/extension-example",
      title: "Hello World",
      components: {
        Page: () => <ExamplePage extension={this}/>,
        MenuIcon: ExampleIcon,
      }
    }
  ]
}

Cluster pages are objects matching the PageRegistration interface. The path field sets the page route, and is used in associating the page with an invocation action such as a menu selection. The title field is what is shown in the side bar used to activate the page. The components field specifies Page, the page definition, and an optional icon (MenuIcon field) that is shown next to the 'title' in the side bar list. Both Page and MenuIcon are React.ComponentTypes. In this example ExamplePage and ExampleIcon are defined in page.tsx:

import { LensRendererExtension, Component } from "@k8slens/extensions";
import React from "react"

export function ExampleIcon(props: Component.IconProps) {
  return <Component.Icon {...props} material="pages" tooltip="Hello"/>
}

export class ExamplePage extends React.Component<{ extension: LensRendererExtension }> {
  render() {
    return (
      <div>
        <p>Hello world!</p>
      </div>
    )
  }
}

Note that the ExamplePage class defines a property named extension. This allows the ExampleExtension object to be passed in React-style in the cluster page definition, so that ExamplePage can access any ExampleExtension subclass data.

globalPages

Global pages appear independently of the cluster dashboard. A global page is typically triggered by a custom app menu selection from a Main Extension or a custom status bar item. Global pages can be visible even when there is no active cluster. It is conventional to use a global page to show information and provide functionality relevant across clusters, along with custom data and functionality your extension may have.

The following example adds a global page definition to a LensRendererExtension subclass:

import { LensRendererExtension } from '@k8slens/extensions';
import { MyPage } from './page';
import React from 'react';

export default class ExtensionRenderer extends LensRendererExtension {
  globalPages = [
    {
      path: "/my-extension-path",
      hideInMenu: true,
      components: {
        Page: () => <MyPage extension={this} />,
      },
    },
  ];
}

clusterFeatures

Cluster features are Kubernetes resources that can applied and managed to the active cluster. They can be installed/uninstalled from the cluster settings page. The following example shows how to add a cluster feature:

import { LensRendererExtension } from "@k8slens/extensions"
import { MetricsFeature } from "./src/metrics-feature"
import React from "react"

export default class ClusterMetricsFeatureExtension extends LensRendererExtension {
  clusterFeatures = [
    {
      title: "Metrics Stack",
      components: {
        Description: () => {
          return (
            <span>
                Enable timeseries data visualization (Prometheus stack) for your cluster.
                Install this only if you don't have existing Prometheus stack installed.
                You can see preview of manifests <a href="https://github.com/lensapp/lens/tree/master/extensions/lens-metrics/resources" target="_blank">here</a>.
              </span>
          )
        }
      },
      feature: new MetricsFeature()
    }
  ]
}

The title and components.Description fields appear on the cluster settings page. The cluster feature must extend the abstract class ClusterFeature.Feature, and specifically implement the following methods:

  abstract install(cluster: Cluster): Promise<void>;
  abstract upgrade(cluster: Cluster): Promise<void>;
  abstract uninstall(cluster: Cluster): Promise<void>;
  abstract updateStatus(cluster: Cluster): Promise<ClusterFeatureStatus>;

appPreferences

The Preferences page is essentially a global page. Extensions can add custom preferences to the Preferences page, thus providing a single location for users to configure global, for Lens and extensions alike.

import React from "react"
import { LensRendererExtension } from "@k8slens/extensions"
import { myCustomPreferencesStore } from "./src/my-custom-preferences-store"
import { MyCustomPreferenceHint, MyCustomPreferenceInput } from "./src/my-custom-preference"


export default class ExampleRendererExtension extends LensRendererExtension {
  appPreferences = [
    {
      title: "My Custom Preference",
      components: {
        Hint: () => <MyCustomPreferenceHint/>,
        Input: () => <MyCustomPreferenceInput store={myCustomPreferencesStore}/>
      }
    }
  ]
}

statusBarItems

The Status bar is the blue strip along the bottom of the Lens UI. Status bar items are React.ReactNode types, which can be used to convey status information, or act as a link to a global page.

The following example adds a status bar item definition, as well as a global page definition, to a LensRendererExtension subclass, and configures the status bar item to navigate to the global upon a mouse click:

import { LensRendererExtension, Navigation } from '@k8slens/extensions';
import { MyStatusBarIcon, MyPage } from './page';
import React from 'react';

export default class ExtensionRenderer extends LensRendererExtension {
  globalPages = [
    {
      path: "/my-extension-path",
      hideInMenu: true,
      components: {
        Page: () => <MyPage extension={this} />,
      },
    },
  ];

  statusBarItems = [
    {
      item: (
        <div
          className="flex align-center gaps hover-highlight"
          onClick={() => Navigation.navigate(this.globalPages[0].path)}
        >
          <MyStatusBarIcon />
          <span>My Status Bar Item</span>
        </div>
      ),
    },
  ];
}

kubeObjectMenuItems

An extension can add custom menu items (including actions) for specified Kubernetes resource kinds/apiVersions. These menu items appear under the ... for each listed resource, and on the title bar of the details page for a specific resource.

import React from "react"
import { LensRendererExtension } from "@k8slens/extensions";
import { CustomMenuItem, CustomMenuItemProps } from "./src/custom-menu-item"

export default class ExampleExtension extends LensRendererExtension {
  kubeObjectMenuItems = [
    {
      kind: "Node",
      apiVersions: ["v1"],
      components: {
        MenuItem: (props: CustomMenuItemProps) => <CustomMenuItem {...props} />
      }
    }
  ]
}

kubeObjectDetailItems

An extension can add custom details (content) for specified Kubernetes resource kinds/apiVersions. These custom details appear on the details page for a specific resource.

import React from "react"
import { LensRendererExtension } from "@k8slens/extensions";
import { CustomKindDetails, CustomKindDetailsProps } from "./src/custom-kind-details"

export default class ExampleExtension extends LensRendererExtension {
  kubeObjectMenuItems = [
    {
      kind: "CustomKind",
      apiVersions: ["custom.acme.org/v1"],
      components: {
        Details: (props: CustomKindDetailsProps) => <CustomKindDetails {...props} />
      }
    }
  ]
}