Docker for building apps and one-off jobs

Unlike virtual machines, launching, which is associated with significant human and computational costs, Docker is often used to perform one-time actions when software needs to be launched one-time, and it is desirable not to spend effort on installing and removing it. To do this, a container is launched, which is mounted to the folder with our application, which performs the required actions on it and, after they are completed, is deleted. An example is a JavaScript project for which you need to build and run tests. At the same time, the project itself does not use NodeJS, but contains only collector configs, for example, WEBPack, and written tests. To do this, we start the build container in iterative mode, in which you can control the build process, if necessary, and after the build is completed, the container will stop and delete itself, for example, you can run something like this at the root of the application: docker run -it –rm -v $ (pwd): app node-build . Tests can be carried out in a similar way. As a result, the application is built and tested on a test server, but the software that is not required for its operation on the production server will not be adopted and will not consume resources, and can be transferred to the production server, for example, using a container. In order not to write documentation on starting the build and testing, you can put two corresponding configs Docker-compose-build.yml and Docker-compose-test.yml and call them Docker-compose up -f ./docker-compose-build.

Management and access

We manage containers using the Docker command . Now, let's say there is a need to manage remotely. Using VNC, SSH, or something else to manage your Docker team will probably be too time consuming if the task gets complicated. That's right, first you will need to figure out what Docker is, because the Docker command and the Docker program are not the same thing, or rather, the Docker command is a console client for managing the Docker Engine client-server application. The team interacts with the Docker Machine server through the Docker REST API, which is intended for remote interaction with the server. But, in this case, you need to take care of authorization and SSL-encryption of traffic. This is ensured by the creation of keys, but in general, if the task is centralized management, differentiation of rights and security, it is better to look towards products that initially provide this and use Docker as a container launch, and not as a system.

By default, for security reasons, the client communicates with the server over a Unix socket (special file /var/run/socket.sock), not over a network socket. To work through a Unix socket, you can tell the curl sending program to use curl –unix-socket /var/run/docker.sock http: /v1.24/containers/json , but this feature is supported since curl 1.40, which is not supported on CentOS. To solve this problem and to communicate between remote servers, we use a network socket. To activate it, stop the systemctl server stop docker and start it with the settings dockerd -H tcp: //0.0.0.0: 9002 & (listen to everyone on port 9002, which is not permissible for production). After running, the docker ps command will not work, but docker -H 5.23.52.111:9002 ps or docker -H tcp: //geocode1.essch.ru: 9202 ps . By default, Docker uses port 2375 for http, and 2376 for https. In order not to change the code everywhere and not to specify the socket every time, we will write it in the environment variables: