将 Docker 图像保存 IP 地址从 Windows 转移到 ZEDC9F0A5A5D57797BF68E373647438

Question

I'm very new to Docker (in fact I've been only using it for one day) so maybe I'm misunderstanding some basic concept but I couldn't find a solution myself.

Here's the problem. I have an ASP.NET Core server application on a Windows machine. It uses MongoDB as a datastore. Everything works fine. I decided to pack all this stuff into Docker containers and put it to a Linux (Ubuntu Server 18.04) server. I've packed mongo to a container so now its PUBLISHED IP:PORT value is 192.168.99.100:32772 I've hardcoded this address to my ASP.NET server and also packed it to a container (IP 192.168.99.100:5000). Now if I run my server and mongo containers together on my Windows machine, they work just fine. The server connects to a container with the database and can do whatever it needs.

But when I transfer both containers to Ubuntu and run them, the server cannot connect to the database because this IP address is not available there. I've beed googling for a few hours to find a solution and still I'm struggling with it. What is the correct way to go about thes IP addresses? Is it possible to set an IP that will be the same for a container regardless of environment?

Answer 1

I recommend using docker-compose for the purpose you described above.

With docker-compose, you can access the database via a service name instead of an IP (which potentially is not available on another system). Here two links to get started

• https://docs.docker.com/compose/gettingstarted/
• https://docs.docker.com/compose/compose-file/

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Updated answer (10.11.2019)

Here a concrete example for your asp.net app:

docker-compose.yaml

version: "3"
services:
  frontend:
    image: fqdn/aspnet:tag
    ports:
    - 8080:80
    links:
    - database
  database:
    image: mongo
    environment:
      MONGO_INITDB_DATABASE: "mydatabase"
      MONGO_INITDB_ROOT_USERNAME: "root"
      MONGO_INITDB_ROOT_PASSWORD: "example"
    volumes:
    - myMongoVolume:/data/db

volumes:
  myMongoVolume: {}

From the frontend container, you can reach the mongo db container via the service name "database" (instead of an IP). Due to the link definition in the frontend service, the frontend service will start after the linked service (database).

Through volume definition, the mongo database will be stored in a volume that persists independently from the container lifecycle.

Additionally, I assume you want to reach the asp.net application via the host IP. I do not know the port that you expose in your application so I assume the default port 80. Via the ports section in the frontend, we define that container port 80 is exposed as port 8080 on the host IP. eg you can open your browser and type your host IP and port 8080 eg 127.0.0.1:8080 for localhost and reach your application.

With docker-compose installed, you can start your app, which consists of your frontend and database service via

docker-compose up

Available command options for docker-compose can be found here

• https://docs.docker.com/compose/reference/overview/

Install instructions for docker-compose

• https://docs.docker.com/compose/install/

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Updated answer (10.11.2019, v2)

From the comment section

Keep in mind that you need to connect via the servicename (eg database) and the correct port. For MongoDB that port is 27017. That would tanslate to database:27017 in your frontend config

Q: will mongo also be available from the outside in this case?

A: No, since the service does not contain any port definition the database itself will not be directly reachable. From a security standpoint, this is preferable.

Q: could you expain this

volumes:
  myMongoVolume: {}     

A: in the service definition for your database service, we have specified a volume to store the database itself to make the data independent from the container lifecycle. However just by defining a volume in the service section the volume will not be created. Through the definition in the volume section, we create the volume myMongoVolume with the default settings (indicated through {} ). If you would like to customize your volume you can do so in this volumes section of your docker-compose.yaml. More information regarding volumes can be found here

• https://docs.docker.com/compose/compose-file/#volume-configuration-reference

eg if you would like to use a specific storage driver for your volume or use an external storage.