Most of the time you can be well off running your app on your local machine and use containers only to sandbox your databases and messaging queues, but some bugs will show themselves only when the app itself is containerized as well. In case you’re wondering: “Why should I acquire this knowledge?” The answer is simple: Node.js is free of locks, so there's no chance to dead-lock any process. Learn about debugging Node.In this post, we’ll take a look at how you can debug a Node.js Node.js is an asynchronous event-driven JavaScript runtime and is the most effective when building scalable network applications.You're done! Now that your container is ready, you may want to: The output will be displayed in the terminal. In the Containers tab, right-click on your container and choose View Logs. You can view the logs in VS Code by using the View Logs command on the container: You can configure the application to wait for the debugger to attach before starting execution by setting the inspectMode property to break in the docker-run: debug task in tasks.json under the node object. Note that, because the debugger attaches after the application starts, the breakpoint may be missed the first time around you might have to refresh the browser to see the debugger break on the second try. The debugger stops at the breakpoint in index.js.The browser opens to the (random) port mapped to the service container.The Docker container for the service runs.The Docker image for the service builds.Make sure the Docker Node.js Launch debugger configuration is selected. Set a breakpoint in the get() handler for the '/' route in routes/index.js. The extension detects the protocol and port used by the service and points the browser to the service. vscode/launch.json for debugging the service when running inside a container. When the Docker extension adds files to the application, it also adds a VS Code debugger configuration in. When done testing, right-click the container in the Containers tree and select Stop. The container should start and you should be able to see it in the Docker Containers tree: Right-click on the image built in the previous section and select Run or Run Interactive. Open the Docker Explorer and verify that the new image is visible in the Images tree: Open the Command Palette ( ⇧⌘P (Windows, Linux Ctrl+Shift+P)) and select the Docker Images: Build Image. When done testing, type Ctrl+C in the terminal. Open the web browser and navigate to You should see a page similar to the following: Open a terminal ( ⌃` (Windows, Linux Ctrl+`)).Įnter npm run start to start the application: > start /Users/user/code/scratch/express-app Put the environment variable definition in the base stage to have this variable available in both debug and release versions of the container image. The Docker extension uses the base stage of the Dockerfile to create a debug version of the container image for your service. Note how the Docker extension lists all available Dockerfile instructions and describes the syntax. Use ENV instruction to add an environment variable to the service container image. To see this feature in action, add an environment variable to your service image by following these steps: The Docker extension helps you author Dockerfiles by using IntelliSense to provide auto-completions and contextual help. vscode/launch.json for debugging the service within the container. vscode/tasks.json for building and running the container (in both debug- and release-configurations) and a launch debug configuration in. Finally, the extension will create a set of VS Code tasks in. If you elected to include Docker Compose files, docker-compose.yml and will be generated as well. Compose is typically used when running multiple containers at once. Select either Yes or No when prompted to include Docker Compose files. Select Node.js when prompted for the application platform.Įnter 3000 when prompted for the application port. Open the Command Palette ( ⇧⌘P (Windows, Linux Ctrl+Shift+P)) and use Docker: Add Docker Files to Workspace. Open a development command prompt in the project folder and create the project: npx express-generator npm install Both Docker and the VS Code Docker extension must be installed as described in the overview.Debug the service running within a container.Build, run, and verify the functionality of the service.Create a Dockerfile file for an Express Node.js service container.Configure IntelliSense for cross-compiling.
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