To get the IP address of a Node.js app running in a Docker container, you can use the following methods:

  1. Using docker inspect: You can use the docker inspect command to retrieve detailed information about a running container, including its network settings, which includes the container's IP address.

    # Replace 'container_name_or_id' with the actual name or ID of your container docker inspect -f '{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' container_name_or_id

    This command will output the IP address of the specified container.

  2. Docker DNS Name: By default, Docker provides DNS resolution for container names, allowing you to access other containers by their names. You can use the container name as the hostname to connect to the Node.js app from other containers, and Docker will resolve it to the container's IP address automatically.

    For example, if your Node.js app is running in a container named my_node_app, other containers can access it using the hostname my_node_app.

  3. Using Environment Variable: You can set up an environment variable inside your Node.js app's Docker container to store its IP address. When the container starts, you can query the container's IP address and store it in the environment variable. Then, your Node.js app can access the IP address through the environment variable.

    Here's an example of how you can set an environment variable for the IP address in your Dockerfile:

    FROM node:14 # Copy your Node.js app files COPY . /app # Set an environment variable for the container's IP address ENV CONTAINER_IP=$(hostname -i) # Set the working directory and install dependencies WORKDIR /app RUN npm install # Start your Node.js app CMD ["node", "app.js"]

    In this example, the environment variable CONTAINER_IP will contain the container's IP address, and your Node.js app can access it using process.env.CONTAINER_IP.

Remember that the container's IP address can change each time it restarts or is recreated. If you need a more stable way to access the Node.js app from outside the Docker network, you may consider using port mapping (-p option) when running the container, or using an external load balancer or reverse proxy to route traffic to the container.

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