Wondering what Docker Compose is?

Docker is the most popular containerization tool in the DevOps world. But, What is Docker Compose?

Docker Compose is used to run applications which have multiple containers using a YAML file.

There can be several cases where the docker application must run multiple containers for different technology stack. Now building, running, connecting separate dockerfiles for each container can be a difficult task; this is where docker-compose helps you out.

Using a single and straightforward docker-compose.yml file, you can build, connect, and launch all the containers by running a single command. This is very useful for enterprise applications in production, where several applications run inside containers. It saves a lot of time by running 100s of application inside docker containers with ease.

Installing Docker Compose

Docker should already be installed on your system before installing compose.

Run the command below to install docker-compose.

[email protected]:/home/geekflare$ sudo curl -L "https://github.com/docker/compose/releases/download/1.23.1/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose

[sudo] password for geekflare:

% Total    % Received % Xferd  Average Speed   Time    Time     Time  Current

Dload  Upload   Total   Spent    Left  Speed

100   617    0   617    0     0   1209      0 --:--:-- --:--:-- --:--:--  1209

100 11.1M  100 11.1M    0     0   348k      0  0:00:32  0:00:32 --:--:--  476k

Run the command below to set file permissions.

[email protected]:/home/geekflare$ sudo chmod +x /usr/local/bin/docker-compose

Check if it got installed correctly, it should return the docker-compose version.

[email protected]:/home/geekflare$ docker-compose --version

docker-compose version 1.23.1, build b02f1306

Below is the list of commands you can use with docker-compose.

[email protected]:/home/geekflare$ docker-compose

Define and run multi-container applications with Docker.

Usage:

docker-compose [-f <arg>…] [options] [COMMAND] [ARGS…]

docker-compose -h|--help

Options:

-f, --file FILE             Specify an alternate compose file

(default: docker-compose.yml)

-p, --project-name NAME     Specify an alternate project name

(default: directory name)

--verbose                   Show more output

--log-level LEVEL           Set log level (DEBUG, INFO, WARNING, ERROR, CRITICAL)

--no-ansi                   Do not print ANSI control characters

-v, --version               Print version and exit

-H, --host HOST             Daemon socket to connect to


--tls                       Use TLS; implied by –tlsverify

--tlscacert CA_PATH         Trust certs signed only by this CA

--tlscert CLIENT_CERT_PATH  Path to TLS certificate file

--tlskey TLS_KEY_PATH       Path to TLS key file

--tlsverify                 Use TLS and verify the remote

--skip-hostname-check       Don’t check the daemon’s hostname against the

name specified in the client certificate

--project-directory PATH    Specify an alternate working directory

(default: the path of the Compose file)

--compatibility             If set, Compose will attempt to convert deploy

keys in v3 files to their non-Swarm equivalent

Commands:

build              Build or rebuild services

bundle             Generate a Docker bundle from the Compose file

config             Validate and view the Compose file

create             Create services

down               Stop and remove containers, networks, images, and volumes

events             Receive real time events from containers

exec               Execute a command in a running container

help               Get help on a command

images             List images

kill               Kill containers

logs               View output from containers

pause              Pause services

port               Print the public port for a port binding

ps                 List containers

pull               Pull service images

push               Push service images

restart            Restart services

rm                 Remove stopped containers

run                Run a one-off command

scale              Set number of containers for a service

start              Start services

stop               Stop services

top                Display the running processes

unpause            Unpause services

up                 Create and start containers

version            Show the Docker-Compose version information

Docker Compose File

Here is a sample docker-compose file which does all the magic.

version: '3'

services:

web:

build: .

ports:

- "5000:5000"

redis:

image: "redis:alpine"

The first line in this file specifies the version being used. This number depends on the Docker engine installed on your system. I have Docker 18.09.6 installed which belongs to version 3 of docker-compose. Check out more details on versions here – https://docs.docker.com/compose/compose-file/compose-versioning/

This docker file is running two services/applications, web and Redis. The web service is built through a dockerfile and runs at default flask webserver port – 5000. The Redis service runs by pulling the Redis image from docker hub registry.

To execute the docker-compose.yml file, you need to run a very simple command: docker-compose up

Docker Compose Workflow

Below are the three steps to use docker-compose.

  1. Create dockerfile of each service
  2. Create a docker-compose.yml file to connect all the dockerfiles
  3. Run docker-compose up command to start the system

Let me take an example of the sample docker-compose file we saw earlier and show you how the project structure will be created.

my-app

|-----web

|---------Dockerfile

|-----redis

|docker-compose.yml

my-app is my main project directory. This directory has web and Redis service directories and the docker-compose YAML file. Dockerfile of Web service is present in a web directory. Since Redis service is being pulled from docker hub directly, no dockerfile is required in Redis directory. This is how docker-compose workflow looks like.

Containerizing A MEAN Stack Application using Docker Compose

Now that you have understood fundamental concepts. Let me show a demo on how to containerize a MEAN stack application using docker-compose.

MEAN stands for MongoDB, Express, Angular and Node.js. Applications using these services together is also called a MEAN/Full-stack application.

For this demo, we will run three docker containers:

  • Container 1 – Angular
  • Container 2 – NodeJS and ExpressJS
  • Container 3 – MongoDB

Download the complete application here: http://bit.ly/2St7r3A (not tested for production)

This is how my docker-compose.yml file will look like to run these three containers:

version: '3'

services:

angular:

build: angular-client

ports:

- "4200:4200"

volumes:

- ./angular-client/:/var/www/app

express:

build: express-server

ports:

- "3000:3000"

volumes:

- ./express-server/:/var/www/app

links:

- database

database:

image: mongo

ports:

- "27017:27017"
  • The first line specifies the docker-compose version being used
  • We are running three services – angular, express and database
  • Angular service will be built using a dockerfile. It will run on port 4200, and the application volume is /var/www/app
  • Express service will be built using a dockerfile. The express server will run at port 3000, and the volume is /var/www/app
  • Database service will pull MongoDB image from dockerhub and start it at post 27017

Extract the project in the home directory and go to the angular-client directory.

[email protected]:~$ cd mean

[email protected]:~/mean$ cd angular-client 

Run the command below if you don’t have node package manager (npm) installed on your system (ignore if it’s installed).

[email protected]:~/mean/angular-client$ sudo apt install npm

[sudo] password for geekflare:

Reading package lists... Done

Building dependency tree

Reading state information... Done

The following additional packages will be installed:

gyp javascript-common libc-ares2 libhttp-parser2.8 libjs-async libjs-inherits libjs-is-typedarray

libjs-jquery libjs-node-uuid libjs-underscore libssl1.0-dev libuv1 libuv1-dev node-abbrev node-ajv

node-ansi node-ansi-color-table node-ansi-regex node-ansi-styles node-ansistyles node-aproba node-archy

node-are-we-there-yet node-async node-aws-sign2 node-balanced-match node-block-stream node-bluebird

node-boom node-brace-expansion node-builtin-modules node-camelcase node-caseless node-chalk node-cliui

node-clone node-co node-color-convert node-color-name node-combined-stream node-concat-map

node-config-chain node-console-control-strings node-cookie-jar node-copy-concurrently node-core-util-is

node-yallist node-yargs node-yargs-parser nodejs nodejs-dev nodejs-doc

Suggested packages:

apache2 | lighttpd | httpd node-aws-sign node-oauth-sign node-http-signature debhelper

The following NEW packages will be installed:

gyp javascript-common libc-ares2 libhttp-parser2.8 libjs-async libjs-inherits libjs-is-typedarray

libjs-jquery libjs-node-uuid libjs-underscore libssl1.0-dev libuv1 libuv1-dev node-abbrev node-ajv

node-ansi node-ansi-color-table node-ansi-regex node-ansi-styles node-ansistyles node-aproba node-archy

node-are-we-there-yet node-async node-aws-sign2 node-balanced-match node-block-stream node-bluebird

0 upgraded, 212 newly installed, 0 to remove and 233 not upgraded.

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Extracting templates from packages: 100%

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Processing triggers for libc-bin (2.28-0ubuntu1) ...

In angular-client directory and run npm install.

[email protected]:~/mean/angular-client$ npm install

> [email protected] install /home/geekflare/mean/angular-client/node_modules/uws

> node-gyp rebuild > build_log.txt 2>&1 || exit 0

> [email protected] install /home/geekflare/mean/angular-client/node_modules/node-sass

> node scripts/install.js

Downloading binary from https://github.com/sass/node-sass/releases/download/v4.7.2/linux-x64-57_binding.node

Download complete  ] - :

Binary saved to /home/geekflare/mean/angular-client/node_modules/node-sass/vendor/linux-x64-57/binding.node

Caching binary to /home/geekflare/.npm/node-sass/4.7.2/linux-x64-57_binding.node

> [email protected] postinstall /home/geekflare/mean/angular-client/node_modules/webpack/node_modules/uglifyjs-webpack-plugin

> node lib/post_install.js

> [email protected] postinstall /home/geekflare/mean/angular-client/node_modules/node-sass

> node scripts/build.js

Binary found at /home/geekflare/mean/angular-client/node_modules/node-sass/vendor/linux-x64-57/binding.node

Testing binary

Binary is fine

added 1457 packages from 1250 contributors in 80.009s

Now go to express directory and run npm install.

[email protected]:~/mean/angular-client$ cd ..

[email protected]:~/mean$ cd express-server/

[email protected]:~/mean/express-server$ npm install

Now that everything is set, its time to run docker-compose.yml file which is going to launch all the docker containers and run the MEAN stack application.

[email protected]:~/mean/express-server$ cd ..

[email protected]:~/mean$ docker-compose up

Creating network "mean_default" with the default driver

Building angular

Step 1/8 : FROM node:8

8: Pulling from library/node

a4d8138d0f6b: Pull complete

dbdc36973392: Pull complete

f59d6d019dd5: Pull complete

aaef3e026258: Pull complete

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012886364728: Pull complete

Digest: sha256:310db2abcff097ef44af205d81833282a6d5471002a1b59d7b7459a74152c856

Status: Downloaded newer image for node:8

---> 8e45c884a32e

Step 2/8 : RUN mkdir -p /var/www/app

---> Running in c70a0cab7994

Removing intermediate container c70a0cab7994

---> 001c5e840b24

Step 3/8 : WORKDIR /var/www/app

---> Running in 622ebdc41b2f

Removing intermediate container 622ebdc41b2f

---> baa2e2347259

Step 4/8 : COPY package.json /var/www/app

---> 5b97543befab

Step 5/8 : RUN npm install

---> Running in 73e3d8b7a701

> [email protected] install /var/www/app/node_modules/uws

> node-gyp rebuild > build_log.txt 2>&1 || exit 0

> [email protected] install /var/www/app/node_modules/node-sass

> node scripts/install.js

Downloading binary from https://github.com/sass/node-sass/releases/download/v4.12.0/linux-x64-57_binding.node

Download complete

Binary saved to /var/www/app/node_modules/node-sass/vendor/linux-x64-57/binding.node

Caching binary to /root/.npm/node-sass/4.12.0/linux-x64-57_binding.node

> [email protected] postinstall /var/www/app/node_modules/core-js

> node scripts/postinstall || echo "ignore"

The project needs your help! Please consider supporting of core-js on Open Collective or Patreon:

> https://opencollective.com/core-js

> https://www.patreon.com/zloirock

> [email protected] postinstall /var/www/app/node_modules/webpack/node_modules/uglifyjs-webpack-plugin

> node lib/post_install.js

> [email protected] postinstall /var/www/app/node_modules/node-sass

> node scripts/build.js

Binary found at /var/www/app/node_modules/node-sass/vendor/linux-x64-57/binding.node

Testing binary

Binary is fine

added 1606 packages from 1329 contributors and audited 15092 packages in 112.427s

Removing intermediate container 73e3d8b7a701

---> 55790d2fae93

Step 6/8 : COPY . /var/www/app

---> 61537aa487f4

Step 7/8 : EXPOSE 4200

---> Running in 632eedc35a45

Removing intermediate container 632eedc35a45

---> 51e75b0e2ebe

Step 8/8 : CMD ["npm", "start"]

---> Running in 36bbb12a0d38

Removing intermediate container 36bbb12a0d38

---> 9f8d61db600c

Successfully built 9f8d61db600c

Successfully tagged mean_angular:latest

Pulling database (mongo:)...

latest: Pulling from library/mongo

35b42117c431: Pull complete

ad9c569a8d98: Pull complete

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0c175077525d: Pull complete

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c1956a9e136a: Pull complete

4c35cf22b1d5: Pull complete

Building express

Step 1/9 : FROM node:8

---> 8e45c884a32e

Step 2/9 : RUN mkdir -p /var/www/app

---> Using cache

---> 001c5e840b24

Step 3/9 : WORKDIR /var/www/app

---> Using cache

---> baa2e2347259

Step 4/9 : COPY package.json /var/www/app

---> 0232ad53c679

Step 5/9 : RUN npm install

---> Running in c309bf6f218e

added 128 packages from 151 contributors and audited 233 packages in 9.055s

Removing intermediate container c309bf6f218e

---> 49e652884562

Step 6/9 : RUN npm install -g nodemon

---> Running in 0ed5d7f3642b

/usr/local/bin/nodemon -> /usr/local/lib/node_modules/nodemon/bin/nodemon.js

> [email protected] postinstall /usr/local/lib/node_modules/nodemon

> node bin/postinstall || exit 0

Love nodemon? You can now support the project via the open collective:

> https://opencollective.com/nodemon/donate

+ [email protected]

added 221 packages from 128 contributors in 18.856s

Removing intermediate container 0ed5d7f3642b

---> 32c55606f35e

Step 7/9 : COPY . /var/www/app

---> a618b38a2812

Step 8/9 : EXPOSE 3000

---> Running in bea389ab3ef1

Removing intermediate container bea389ab3ef1

---> 684bbfb31371

Step 9/9 : CMD ["npm", "start"]

---> Running in 9aa1b72e4a4e

Removing intermediate container 9aa1b72e4a4e

---> 35dcb3df9806

Successfully built 35dcb3df9806

Successfully tagged mean_express:latest

Creating mean_angular_1_de44b3f5b988  ... done

Creating mean_database_1_708f8f9c3c33 ... done

Creating mean_express_1_b57a483a72ee  ... done

Attaching to mean_angular_1_f257e2233ef1, mean_database_1_ccc5c677e00b, mean_express_1_574f07b045fc

angular_1_f257e2233ef1 |

angular_1_f257e2233ef1 | > [email protected] start /var/www/app

angular_1_f257e2233ef1 | > ng serve -H 0.0.0.0

angular_1_f257e2233ef1 |

database_1_ccc5c677e00b | 2019-07-20T22:33:25.933+0000 I CONTROL  [main] Automatically disabling TLS 1.0, to force-enable TLS 1.0 specify --sslDisabledProtocols 'none'

database_1_ccc5c677e00b | 2019-07-20T22:33:25.937+0000 I CONTROL  [initandlisten] MongoDB starting : pid=1 port=27017 dbpath=/data/db 64-bit host=f74b56905249

database_1_ccc5c677e00b | 2019-07-20T22:33:25.937+0000 I CONTROL  [initandlisten] db version v4.0.10

database_1_ccc5c677e00b | 2019-07-20T22:33:25.937+0000 I CONTROL  [initandlisten] git version: c389e7f69f637f7a1ac3cc9fae843b635f20b766

database_1_ccc5c677e00b | 2019-07-20T22:33:25.937+0000 I CONTROL  [initandlisten] OpenSSL version: OpenSSL 1.0.2g  1 Mar 2016

database_1_ccc5c677e00b | 2019-07-20T22:33:25.937+0000 I CONTROL  [initandlisten] allocator: tcmalloc

database_1_ccc5c677e00b | 2019-07-20T22:33:25.937+0000 I CONTROL  [initandlisten] modules: none

database_1_ccc5c677e00b | 2019-07-20T22:33:25.937+0000 I CONTROL  [initandlisten] build environment:

database_1_ccc5c677e00b | 2019-07-20T22:33:25.937+0000 I CONTROL  [initandlisten]     distmod: ubuntu1604

database_1_ccc5c677e00b | 2019-07-20T22:33:25.937+0000 I CONTROL  [initandlisten]     distarch: x86_64

database_1_ccc5c677e00b | 2019-07-20T22:33:25.937+0000 I CONTROL  [initandlisten]     target_arch: x86_64

database_1_ccc5c677e00b | 2019-07-20T22:33:25.937+0000 I CONTROL  [initandlisten] options: { net: { bindIpAll: true } }

express_1_574f07b045fc |

express_1_574f07b045fc | > [email protected] start /var/www/app

express_1_574f07b045fc | > nodemon ./bin/www

express_1_574f07b045fc |

express_1_574f07b045fc | [nodemon] 1.19.1

express_1_574f07b045fc | [nodemon] to restart at any time, enter `rs`

express_1_574f07b045fc | [nodemon] watching: *.*

express_1_574f07b045fc | [nodemon] starting `node ./bin/www`

database_1_ccc5c677e00b | 2019-07-20T22:33:33.543+0000 I NETWORK  [listener] connection accepted from 172.19.0.4:38958 #1 (1 connection now open)

database_1_ccc5c677e00b | 2019-07-20T22:33:33.560+0000 I NETWORK  [conn1] received client metadata from 172.19.0.4:38958 conn1: { driver: { name: "nodejs", version: "3.0.1" }, os: { type: "Linux", name: "linux", architecture: "x64", version: "4.18.0-25-generic" }, platform: "Node.js v8.16.0, LE, mongodb-core: 3.0.1" }

express_1_574f07b045fc | mongodb: connected

angular_1_f257e2233ef1 | ** NG Live Development Server is listening on 0.0.0.0:4200, open your browser on http://localhost:4200/ **

angular_1_f257e2233ef1 | Date: 2019-07-21T11:21:03.868Z - Hash: 639d9a968476ed482b5c - Time: 336ms

angular_1_f257e2233ef1 | 4 unchanged chunks

angular_1_f257e2233ef1 | chunk {main} main.bundle.js (main) 19.8 kB [initial] [rendered]

angular_1_f257e2233ef1 |

angular_1_f257e2233ef1 | webpack: Compiled successfully.

angular_1_f257e2233ef1 | webpack: Compiling...

angular_1_f257e2233ef1 | Date: 2019-07-21T11:25:15.661Z - Hash: e5a2b1c1afe0deb396c3 - Time: 251ms

angular_1_f257e2233ef1 | 4 unchanged chunks

angular_1_f257e2233ef1 | chunk {main} main.bundle.js (main) 19.8 kB [initial] [rendered]

angular_1_f257e2233ef1 |

angular_1_f257e2233ef1 | webpack: Compiled successfully.

Go to your browser and check https://localhost:4200, your application will be up and running.

angular - docker compose

Go to https://localhost:3000 to check if an express server is running.

express - docker compose

Also, you can run docker images command to see which all images are present in docker.

[email protected]:~/mean$ docker images

REPOSITORY                 TAG                 IMAGE ID            CREATED             SIZE

mean_express               latest              35dcb3df9806        14 hours ago        923MB

mean_angular               latest              9f8d61db600c        14 hours ago        1.29GB

node                       8                   8e45c884a32e        9 days ago          895MB

mongo                      latest              785c65f61380        2 weeks ago         412MB

Run the command below to see the containers running inside docker.

[email protected]:~/mean$ docker ps

CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS                      NAMES

681c9c34bee2        mean_express        "docker-entrypoint.s…"   14 hours ago        Up 14 hours         0.0.0.0:3000->3000/tcp     mean_express_1_574f07b045fc

f74b56905249        mongo               "docker-entrypoint.s…"   14 hours ago        Up 14 hours         0.0.0.0:27017->27017/tcp   mean_database_1_ccc5c677e00b

260ef1e52dab        mean_angular        "docker-entrypoint.s…"   14 hours ago        Up 14 hours         0.0.0.0:4200->4200/tcp     mean_angular_1_f257e2233ef1

So now, all three docker containers are up and running.

Docker-compose took care of running all the containers with ease. This was a simple example for running three containers; you can imagine how useful it will be if the applications have to be launched on 100s of containers. Go ahead and try out to see how it works.