Demonstrating the use of named pipes created through the mkfifo command for inter-container transfer of data through pipes.
To pipe data from one container to another, this example uses named pipes, a special kind of file that functions in the same way the pipe character | would in a bash command. As a minimal example:
echo "test" | cat
Uses | to send the standard output of the echo "test" command into the standard input of the cat command.
A similar thing can be accomplished using named pipes. To create a named pipe, run:
mkfifo -m a=rw </path/to/named/pipe>
The additional -m a=rw option sets the permissions of the pipe to be read/write for all users.
The instructions below will demonstrate using a named pipe created in this repo using mkfifo -m a=rw ./pipes/pipe and bind mounted onto two docker containers as ~/pipe to transfer data between the containers. This is coordinated through the use of docker-compose.
(Paths in these commands relative to the root of this git repo)
To build yourself:
docker build --tag espinoza09/docker-pipes-source ./source
docker build --tag espinoza09/docker-pipes-dest ./dest
If you are pulling from dockerhub, the images are pulled for you when running docker-compose up -d as described in the next section.
Run the containers in detached mode with:
docker-compose up -d
You can verify the containers are running through:
docker ps -a | grep "docker-pipes"
Attach to each container in a separate terminal with with a
docker attach docker-pipes-[source|dest]
Now, you can output some data to the named pipe located at ~/pipe in the docker-pipes-source container, and receive the data in the docker-pipes-dest container:
[rocky@docker-pipes-source ~]$ echo "test" > pipe
[rocky@docker-pipes-dest ~]$ cat < pipe
Note that the order in which the commands are run doesn't matter, and you could just as well do:
[rocky@docker-pipes-dest ~]$ cat < pipe
[rocky@docker-pipes-source ~]$ echo "test" > pipe
Exit the containers using the exit command, and/or run a docker-compose down.