It's not too hard to get this feature these days. Then, when some change is made to the project's source code, the page in our browser automatically refreshes to reflect the change. The idea behind it is simple - launch a special development server to view your project while it's being developed. restarting due to changes.Modern front-end developers have a lot of tools at their disposal, but the idea of "live reloading" is easily one of the most important. I'll change the response message to something more reflective of the current demo. to restart at any time, enter `rs`Įxample app listening on port 3000 Output of npm run dev > nodemon -watch "./**" -ext "js" -exec "node hello.js" const express = require('express')Ĭonsole.log(`Example app listening on port $, Complete script section of package.jsonĪt this point, if we make any changes, they won't be reflected in the app. npm i express nodemonĬreate a file called hello.js and paste the following. Let's install our dependencies using the command below. "test": "echo \"Error: no test specified\" & exit 1" mkdir -p projects/docker-reload npm init -y Wrote to /private/tmp/test/package.json: Creating the appĬreate a project directory where we will store our files. ![]() Hot Reload in Docker Container - Demoįor this demo, let's set up an express-based nodejs application. The rebuilding approach is less efficient than using volumes, as it requires rebuilding the entire container each time you update the files. If you need to update the files, you can simply rebuild the container, and the new files will be copied. When you build the container, the files from the host system will be copied into the container. To use the COPY command, add the following line to your Dockerfile: COPY /path/on/host /path/in/container The COPY command can be used to copy files from the host system into the container. Rebuilding our container is also an option if, by chance, the volume method does not work. The volume workaround is perfectly sufficient for our uses. docker-compose up The Unorthodox Method - Rebuilding a ContainerĪnother rarely used way is by rebuilding a container. Then, start the containers using the following command. Also, specify the containers needed and any volumes or other configuration options. To use Docker Compose, first define your application in a YAML file. Docker Compose is an extension of Docker itself, which is used for creating multi-container Docker applications and running them in any Docker-supported systems. Using the docker-compose commandĪnother way to update files inside a container without rebuilding it is to use Docker Compose. For example, you could edit a file on the host system, and the changes would be visible inside the container. Now, any changes you make to the files inside the mounted directory on the host system will be reflected in the container. docker run -v myvolume:/path/to/mount myimage Then, start a container and mount the volume using the command below. To use a volume, first, create a volume using the following command. A volume is a separate storage area mounted into a container, allowing you to share files between the host system and the container. Using a Docker volume is one way to update files inside a container without rebuilding it. We'll circumvent this by using docker volumes, which will help us update files inside the container while it runs. This is actually the original principle of Docker. But once an image is built in a docker system, the contents cannot be changed, and we can't view the latest update without creating a new image. ![]() Normally when we save a file and open it, the latest updates can be viewed. Though, a limitation that we may hit as we go on is a hot-reload feature in a local environment. All our dependencies are pre-packaged into the docker image, so running a container of the image without issues is easy. ![]() However, when you need to update a file inside a container, it's often necessary to rebuild the entire container, which can be time-consuming and disruptive to your deployment process.ĭocker solves our problem of running an application anywhere we want without relying on external dependencies. Docker containers are a popular way to deploy applications because they provide a consistent runtime environment regardless of the host system.
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