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4. Create your Node.js application image

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In this step, create the image from the local Express.js app.

Add Docker files

In Visual Studio Code, open the Command Palette (F1), type add docker files to workspace, then select the Docker: Add Docker files to workspace command.

Answer the prompts with the following values:

Prompt Value
Select application platform Node.js
Choose a package.json file myexpressapp\package.json
What port does your app listen on? 3000
Include optional Docker Compose files? No

The command creates a Dockerfile along with some configuration files for Docker compose and a .dockerignore.

Build a Docker image

The Dockerfile describes the environment for your app including the location of the source files and the command to start the app within a container.

  1. Open the Command Palette (F1) and run Docker Images: Build Image to build the image. VS Code uses the Dockerfile in the current folder and gives the image the same name as the current folder.

  2. Once completed, the Terminal panel of Visual Studio Code opens to run the docker build command. The output also shows each step, or layer, that makes up the app environment.

  3. Once built, the image appears in the Docker Explorer under Images, named jse2eexpressserver.

Modify build task to include tag

To push the image to your registry, you must first tag it with the registry name. Change the build task to always build with your Azure registry name.

  1. Open your VS Code's task file, found at ./vscode/tasks.json.

  2. Find the task with the type docker-build.

  3. Add the tag property, using your registry name (YOUR-REGISTRY-NAME), in the dockerBuild property:

    {
    "type": "docker-build",
    "label": "docker-build",
    "platform": "node",
    "dockerBuild": {
        "dockerfile": "${workspaceFolder}/Dockerfile",
        "context": "${workspaceFolder}",
        "pull": true,
        "tag": "YOUR-REGISTRY-NAME.azurecr.io/jse2eexpressserver:latest"
    }
},

    If you build on Linux, configure the task for that operating system:

    {
    "type": "docker-build",
    "label": "docker-build",
    "platform": "node",
    "dockerBuild": {
        "dockerfile": "${workspaceFolder}/Dockerfile",
        "context": "${workspaceFolder}",
        "pull": true,
        "tag": "YOUR-REGISTRY-NAME.azurecr.io/jse2eexpressserver:latest"
        // add this and run "docker buildx install" once to activate buildKit alias (buildx)
        "customOptions": "--platform linux/amd64 --push"
    }
},

  4. As a final step, rebuild so you have the image tagged with your registry. Open the Command Palette (F1) and run Docker Images: Build Image to build the image.

Push the image to a registry

  1. The newly-tagged image appears now as a new node in Docker explorer, under Images and includes the registry name. Expand that node, right-click latest, and select Push. Accept the tag for that image by pressing Enter.

  2. The Terminal panel shows the docker push commands used for this operation. The target registry is determined by the registry specified in the image name.

  3. If the output displays "Authentication required", run az acr login --name <your registry name> in the terminal.

  4. Once completed, expand the Registries node in the Docker extension explorer to see your image in the registry, named jse2eexpressserver.

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