What is the difference between docker-compose ports vs expose

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What is the difference between ports and expose options in docker-compose.yml


Docker Tip #59: Difference between Exposing and Publishing Ports , Difference between Docker and Docker-Compose Docker (individual container​) VS Docker-Compose (several containers) SimpleHTTPRequestHandler # Here we define that we want to start the server on port 1234. You can expose a port through your Dockerfile or use --expose and then publish it with the -P flag. This will bind the exposed port to your Docker host on a random port (verified by running docker container ls ). You can expose a port through your Dockerfile or use --expose and then publish it with the -p 80:80 flag.


ports:

  1. Activates the container to listen for specified port(s) from the world outside of the docker(can be same host machine or a different machine) AND also accessible world inside docker.
  2. More than one port can be specified (that's is why ports not port)

expose:

  1. Activates container to listen for a specific port only from the world inside of docker AND not accessible world outside of the docker.
  2. More than one port can be specified

Compose file version 3 reference, It's exactly the same as when we just exposed a port via EXPOSE or --expose . Docker implicitly exposes a port that is published. The difference between an  ports is used for mapping container ports on your host. Services in a compose file on the other hand all belong to an isolated network . As a result, ports do not need to be remapped because there is no possibility of conflict.


Ports This section is used to define the mapping between the host server and Docker container.

ports:
   - 10005:80

It means the application running inside the container is exposed at port 80. But external system/entity cannot access it, so it need to be mapped to host server port.

Note: you have to open the host port 10005 and modify firewall rules to allow external entities to access the application.

They can use

http://{host IP}:10005

something like this

EXPOSE This is exclusively used to define the port on which application is running inside the docker container.

You can define it in dockerfile as well. Generally, it is good and widely used practice to define EXPOSE inside dockerfile because very rarely anyone run them on other port than default 80 port

A beginner's guide to Docker, I noticed that port 80 was open within a linked container regardless of my mapping. Am I to assume that remapping ports is unnecessary if the  Docker compose expose port to docker managed network not by ip. Ask Question Asked today. What is the difference between docker-compose ports vs expose. 290.


Ports

The ports section will publish ports on the host. Docker will setup a forward for a specific port from the host network into the container. By default this is implemented with a userspace proxy process (docker-proxy) that listens on the first port, and forwards into the container, which needs to listen on the second point. If the container is not listening on the destination port, you will still see something listening on the host, but get a connection refused if you try to connect to that host port, from the failed forward into your container.

Note, the container must be listening on all network interfaces since this proxy is not running within the container's network namespace and cannot reach 127.0.0.1 inside the container. The IPv4 method for that is to configure your application to listen on 0.0.0.0.

Also note that published ports do not work in the opposite direction. You cannot connect to a service on the host from the container by publishing a port. Instead you'll find docker errors trying to listen to the already-in-use host port.

Expose

Expose is documentation. It sets metadata on the image, and when running, on the container too. Typically you configure this in the Dockerfile with the EXPOSE instruction, and it serves as documentation for the users running your image, for them to know on which ports by default your application will be listening. When configured with a compose file, this metadata is only set on the container. You can see the exposed ports when you run a docker inspect on the image or container.

There are a few tools that rely on exposed ports. In docker, the -P flag will publish all exposed ports onto ephemeral ports on the host. There are also various reverse proxies that will default to using an exposed port when sending traffic to your application if you do not explicitly set the container port.

Other than those external tools, expose has no impact at all on the networking between containers. You only need a common docker network, and connecting to the container port, to access one container from another. If that network is user created (e.g. not the default bridge network named bridge), you can use DNS to connect to the other containers.

A Brief Primer on Docker Networking Rules: EXPOSE, -p, -P, --link , EXPOSE does not make the ports of the container accessible to the host. by the service name mentioned in the docker-compose.yml file. What is the difference between docker-compose ports vs expose (4) Ports The ports section will publish ports on the host. Docker will setup a forward for a specific port from the host network into the container.


I totally agree with the answers before. I just like to mention that the difference between expose and ports is part of the security concept in docker. It goes hand in hand with the networking of docker. For example:

Imagine an application with a web front-end and a database back-end. The outside world needs access to the web front-end (perhaps on port 80), but only the back-end itself needs access to the database host and port. Using a user-defined bridge, only the web port needs to be opened, and the database application doesn’t need any ports open, since the web front-end can reach it over the user-defined bridge.

This is a common use case when setting up a network architecture in docker. So for example in a default bridge network, not ports are accessible from the outer world. Therefor you can open an ingresspoint with "ports". With using "expose" you define communication within the network. If you want to expose the default ports you don't need to define "expose" in your docker-compose file.

Difference between ports and expose · Issue #3470 · docker/compose, I'm experimenting with dockerfiles and the use of expose and publish has been a major confusion. And then publish the same port as above when running the image How do I go from development docker-compose.yml to deployed vs Big Data vs Data Analytics · Software Testing Interview Questions  Only specify EXPOSE -> If you EXPOSE a port, the service in the container is not accessible from outside Docker, but from inside other Docker containers. So this is good for inter-container communication. Specify EXPOSE and -p -> If you EXPOSE and -p a port, the service in the container is accessible from anywhere, even outside Docker.


Understanding “EXPOSE” in Dockerfile, What does it mean to EXPOSE a port in your Dockerfile? What is it good even better: consider using docker-compose for your container configurations. Writing​  The docker cli is used when managing individual containers on a docker engine. It is the client command line to access the docker daemon api. The docker-compose cli can be used to manage a multi-container application. It also moves many of the options you would enter on the docker run cli into the docker-compose.yml file for easier reuse.


What is the difference between “expose” and “publish” in Docker , Develop a multi-container app running in a Docker containers using Docker Compose To use Docker Compose in VS Code using the Docker extension, you should Configure the debugging port in docker-compose.debug.yml . When you attach to a service that exposes an HTTP endpoint that returns  It's exactly the same as when we just exposed a port via EXPOSE or --expose. Docker implicitly exposes a port that is published. The difference between an exposed port and a published port is that the published port is available on the host, and we can see that in both "HostConfig" and "NetworkSettings".


Docker EXPOSE Ports · vsupalov.com, With this system, you can write once and use often. So craft a Dockerfile for a part of the stack and re-use it for multiple stacks, by way of docker-compose.yml. Remember, docker-compose.yml