Create an advanced frontend extension

To start creating your extension, you first need a directory with files which range from the extension’s source code to the required extension-specific files. This page provides information on how to set up an extension with a more advanced frontend.

Before you start, make sure you have installed the latest version of Docker Desktop.

Extension folder structure

The quickest way to create a new extension is to run docker extension init my-extension as in the Quickstart. This creates a new directory my-extension that contains a fully functional extension.

Tip

The docker extension init generates a React based extension. But you can still use it as a starting point for your own extension and use any other frontend framework, like Vue, Angular, Svelte, etc. or even stay with vanilla Javascript.

Although you can start from an empty directory or from the react-extension sample folder, it's highly recommended that you start from the docker extension init command and change it to suit your needs.

.
├── Dockerfile # (1)
├── ui # (2)
│   ├── public # (3)
│   │   └── index.html
│   ├── src # (4)
│   │   ├── App.tsx
│   │   ├── index.tsx
│   ├── package.json
│   └── package-lock.lock
│   ├── tsconfig.json
├── docker.svg # (5)
└── metadata.json # (6)

1. Contains everything required to build the extension and run it in Docker Desktop.
2. High-level folder containing your front-end app source code.
3. Assets that aren’t compiled or dynamically generated are stored here. These can be static assets like logos or the robots.txt file.
4. The src, or source folder contains all the React components, external CSS files, and dynamic assets that are brought into the component files.
5. The icon that is displayed in the left-menu of the Docker Desktop Dashboard.
6. A file that provides information about the extension such as the name, description, and version.

Adapting the Dockerfile

Note

When using the docker extension init, it creates a Dockerfile that already contains what is needed for a React extension.

Once the extension is created, you need to configure the Dockerfile to build the extension and configure the labels that are used to populate the extension's card in the Marketplace. Here is an example of a Dockerfile for a React extension:

# syntax=docker/dockerfile:1
FROM --platform=$BUILDPLATFORM node:18.9-alpine3.15 AS client-builder
WORKDIR /ui
# cache packages in layer
COPY ui/package.json /ui/package.json
COPY ui/package-lock.json /ui/package-lock.json
RUN --mount=type=cache,target=/usr/src/app/.npm \
    npm set cache /usr/src/app/.npm && \
    npm ci
# install
COPY ui /ui
RUN npm run build

FROM alpine
LABEL org.opencontainers.image.title="My extension" \
    org.opencontainers.image.description="Your Desktop Extension Description" \
    org.opencontainers.image.vendor="Awesome Inc." \
    com.docker.desktop.extension.api.version="0.3.3" \
    com.docker.desktop.extension.icon="https://www.docker.com/wp-content/uploads/2022/03/Moby-logo.png" \
    com.docker.extension.screenshots="" \
    com.docker.extension.detailed-description="" \
    com.docker.extension.publisher-url="" \
    com.docker.extension.additional-urls="" \
    com.docker.extension.changelog=""

COPY metadata.json .
COPY docker.svg .
COPY --from=client-builder /ui/build ui

Configure the metadata file

In order to add a tab in Docker Desktop for your extension, you have to configure it in the metadata.json file the root of your extension directory.

{
  "icon": "docker.svg",
  "ui": {
    "dashboard-tab": {
      "title": "UI Extension",
      "root": "/ui",
      "src": "index.html"
    }
  }
}

The title property is the name of the extension that is displayed in the left-menu of the Docker Desktop Dashboard. The root property is the path to the frontend application in the extension's container filesystem used by the system to deploy it on the host. The src property is the path to the HTML entry point of the frontend application within the root folder.

For more information on the ui section of the metadata.json, see Metadata.

Build the extension and install it

Now that you have configured the extension, you need to build the extension image that Docker Desktop will use to install it.

docker build --tag=awesome-inc/my-extension:latest .

This built an image tagged awesome-inc/my-extension:latest, you can run docker inspect awesome-inc/my-extension:latest to see more details about it.

Finally, you can install the extension and see it appearing in the Docker Desktop Dashboard.

docker extension install awesome-inc/my-extension:latest

Use the Extension APIs client

To use the Extension APIs and perform actions with Docker Desktop, the extension must first import the @docker/extension-api-client library. To install it, run the command below:

npm install @docker/extension-api-client

Then call the createDockerDesktopClient function to create a client object to call the extension APIs.

import { createDockerDesktopClient } from '@docker/extension-api-client';

const ddClient = createDockerDesktopClient();

When using Typescript, you can also install @docker/extension-api-client-types as a dev dependency. This will provide you with type definitions for the extension APIs and auto-completion in your IDE.

npm install @docker/extension-api-client-types --save-dev

For example, you can use the docker.cli.exec function to get the list of all the containers via the docker ps --all command and display the result in a table.

React Vue Angular Svelte

---

Replace the ui/src/App.tsx file with the following code:

// ui/src/App.tsx
import React, { useEffect } from 'react';
import {
  Paper,
  Stack,
  Table,
  TableBody,
  TableCell,
  TableContainer,
  TableHead,
  TableRow,
  Typography
} from "@mui/material";
import { createDockerDesktopClient } from "@docker/extension-api-client";

//obtain docker desktop extension client
const ddClient = createDockerDesktopClient();

export function App() {
  const [containers, setContainers] = React.useState<any[]>([]);

  useEffect(() => {
    // List all containers
    ddClient.docker.cli.exec('ps', ['--all', '--format', '"{{json .}}"']).then((result) => {
      // result.parseJsonLines() parses the output of the command into an array of objects
      setContainers(result.parseJsonLines());
    });
  }, []);

  return (
    <Stack>
      <Typography data-testid="heading" variant="h3" role="title">
        Container list
      </Typography>
      <Typography
      data-testid="subheading"
      variant="body1"
      color="text.secondary"
      sx={{ mt: 2 }}
    >
      Simple list of containers using Docker Extensions SDK.
      </Typography>
      <TableContainer sx={{mt:2}}>
        <Table>
          <TableHead>
            <TableRow>
              <TableCell>Container id</TableCell>
              <TableCell>Image</TableCell>
              <TableCell>Command</TableCell>
              <TableCell>Created</TableCell>
              <TableCell>Status</TableCell>
            </TableRow>
          </TableHead>
          <TableBody>
            {containers.map((container) => (
              <TableRow
                key={container.ID}
                sx={{ '&:last-child td, &:last-child th': { border: 0 } }}
              >
                <TableCell>{container.ID}</TableCell>
                <TableCell>{container.Image}</TableCell>
                <TableCell>{container.Command}</TableCell>
                <TableCell>{container.CreatedAt}</TableCell>
                <TableCell>{container.Status}</TableCell>
              </TableRow>
            ))}
          </TableBody>
        </Table>
      </TableContainer>
    </Stack>
  );
}

Important

We don't have an example for Vue yet. Fill out the form and let us know if you'd like a sample with Vue.

Important

We don't have an example for Angular yet. Fill out the form and let us know if you'd like a sample with Angular.

Important

We don't have an example for Svelte yet. Fill out the form and let us know if you'd like a sample with Svelte.

---

Policies enforced for the front-end code

Extension UI code is rendered in a separate electron session and doesn't have a node.js environment initialized, nor direct access to the electron APIs.

This is to limit the possible unexpected side effects to the overall Docker Dashboard.

The extension UI code can't perform privileged tasks, such as making changes to the system, or spawning sub-processes, except by using the SDK APIs provided with the extension framework. The Extension UI code can also perform interactions with Docker Desktop, such as navigating to various places in the Dashboard, only through the extension SDK APIs.

Extensions UI parts are isolated from each other and extension UI code is running in its own session for each extension. Extensions can't access other extensions’ session data.

localStorage is one of the mechanisms of a browser’s web storage. It allows users to save data as key-value pairs in the browser for later use. localStorage doesn't clear data when the browser (the extension pane) closes. This makes it ideal for persisting data when navigating out of the extension to other parts of Docker Desktop.

If your extension uses localStorage to store data, other extensions running in Docker Desktop can't access the local storage of your extension. The extension’s local storage is persisted even after Docker Desktop is stopped or restarted. When an extension is upgraded, its local storage is persisted, whereas when it is uninstalled, its local storage is completely removed.

Re-build the extension and update it

Since you have modified the code of the extension, you must build again the extension.

$ docker build --tag=awesome-inc/my-extension:latest .

Once built, you need to update it.

$ docker extension update awesome-inc/my-extension:latest

Now you can see the backend service running in the containers tab of the Docker Desktop Dashboard and watch the logs when you need to debug it.

Tip

You can turn on hot reloading to avoid the need to rebuild the extension every time you make a change.

What's next?

• Add a backend to your extension.
• Learn how to test and debug your extension.
• Learn how to setup CI for your extension.
• Learn more about extensions architecture.
• For more information and guidelines on building the UI, see the Design and UI styling section.
• If you want to set up user authentication for the extension, see Authentication.