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Docker Compose

{id: docker-compose}

Install Docker compose

{id: install-docker-compose}

{aside} Docker compose allows us to configure several docker images to be launched together so they can nicely work together. For example one image holds the database server, another one holds the message-passing system, and the third holds the code of the web application.

Docker compose can run them all at once and can also define the network connectivity between them.

There are several ways to install Docker composer. One of them, if you are familiar with Python, is using pip. {/aside}

pip install docker-compose

Docker compose

{id: docker-compose-0} {i: up} {i: attach} {i: exec}

{aside} The configuration of Docker compose is stored in a YAML file, usually called docker-compose.yml. The following is a very simple example that defines a single Docker container, cleverly named "one" which is based on the Ubuntu 20.04 image. Normally in order for a Docker container to keep running you need to execute some command in them that will keep running. We can achieve the same by configuring the stdin_open and the tty parameters. (They are the same as providing -it on the command line of docker.) {/aside}

{aside} In order to launch the Docker containers we need to cd in the directory where we have the docker-compose.yml file and then type in docker-compose up. This will download the image if necessary and launch the Docker container. {/aside}

cd examples/interactive-shell
$ docker-compose up

In another terminal, but in the same directory you can run one-off commands on the running container:

$ docker exec interactive-shell_one_1 hostname

You can also attach to it:

$ docker attach interactive-shell_one_1

However, when you exit, it will shut down the container.

Docker compose 1st example

{id: docker-compose-1}

provide command line override for CMD/ENTRYPOINT in the compose yaml file

cd examples/compose1
docker-compose up
  • This builds the image based on the Dockerfile and then launches two containers

docker compose - keep running two ways

{id: docker-compose-keep-running-two-ways}

attach to either one of them:

docker-compose exec one sh
ping compose1_one_1

Docker Compose

{id: docker-compose-4}

it keeps and reuses the same container unless you remove it with

docker-compose rm

docker-compose up --build

yum install -y net-tools
ifconfig
route -n
ping one

Docker Compose Redis server and client

{id: docker-compose-redis-server-and-client}

Start the docker containers

docker-compose up -d

Connect to the docker container which has the redis client:

docker exec -it redis_client_1 bash

Try the following commands in the Docker container:

redis-cli -h redis get name
(nil)

redis-cli -h redis set name Foobar
OK


redis-cli -h redis get name
"Foobar"

We provide the hostname redis because that's the name of the service. We don't have to provide the port, but if you'd really want to then try this:

redis-cli -h redis -p 6379 get name

Docker Compose Solr server and curl as client

{id: docker-compose-solr-server-and-curl}

Start the docker containers

docker-compose up -d

Connect to the docker container which has curl installed:

docker exec -it solr_client_1 bash

curl http://solr:8983/solr/

TBD:

curl --request POST \
--url http://solr:8983/api/collections \
--header 'Content-Type: application/json' \
--data '{
  "create": {
    "name": "techproducts",
    "numShards": 1,
    "replicationFactor": 0
  }
}'

Docker Compose MongoDB server

{id: docker-compose-mongodb-server}

In one container start the Docker server, the other one will be the client that is built based on the Dockerfile

The Dockerfile is also based on the official mongodb image as that made it easy to have mongosh already installed.

Start the two containers:

docker-compose up -d

Connect to the client container:

docker exec -it mongodb_client_1 bash

Start the mongodb client and connect to the server running in the other container

mongosh mongodb://mongodb:27017

Docker Compose PostgreSQL server

{id: docker-compose-postgresql-server}

In one container start the Docker server, the other one will be the client that is built based on the Dockerfile

The Dockerfile is built on top of a plain Ubuntu image

Start the two containers:

docker-compose up -d

Connect to the client container:

$ docker exec -it postgresql_client_1 bash

# psql -h postgres --username username -d mydb

It will ask for a password:

Password for user username:

type in password

psql (14.5 (Ubuntu 14.5-0ubuntu0.22.04.1), server 15.1 (Debian 15.1-1.pgdg110+1))
WARNING: psql major version 14, server major version 15.
         Some psql features might not work.
Type "help" for help.

mydb=#

Alternativel, once inside the client docker container we can put the variable of the database in an environment variable and then we can run a command that will not wait for any input.

export PGPASSWORD=password
echo "SELECT CURRENT_TIME" | psql -h postgres -U username mydb

Docker Compose for Perl DBD::Pg (PostgreSQL)

{id: docker-compose-dbd-pg}

These files were used to set up a local development environment for the Perl module DBD::Pg

git clone https://github.com/bucardo/dbdpg.git
cd dbdpg

Put the two files in that folder:

In one terminal start Docker compose:

docker-compose up

In another terminal connect to the client container

docker exec -it dbdpg_client_1 bash

Now you can run the tests:

perl Makefile.PL
make
AUTHOR_TESTING=1
RELEASE_TESTING=1
make test

And you can also generate test coverage report:

cover -test

Docker Compose MySQL server

{id: docker-compose-mysql-server}

docker-compose up -d

docker exec -it mysql_client_1  bash

ping mysql

# mysql -h mysql --password=secret
mysql> SELECT CURRENT_TIMESTAMP;
mysql> exit

# echo "SELECT CURRENT_TIMESTAMP" | mysql -h mysql --password=secret