Did you know? There are more than 300,000 Docker Compose files on GitHub.
Docker Compose is a tool for defining and running multi-container Docker applications. It is an amazing developer tool to create the development environment for your application stack. It allows you to define each component of your application following a clear and simple syntax in YAML files. It works in all environments: production, staging, development, testing, as well as CI workflows. Though Compose files are easy to describe a set of related services but there are couple of problems which has emerged in the past. One of the major concern has been around multiple environments to deploy the application with small configuration differences.
Consider a scenario where you have separate development, test, and production environments for your Web application. Under development environment, your team might be spending time in building up Web application(say, WordPress), developing WP Plugins and templates, debugging the issue etc. When you are in development you’ll probably want to check your code changes in real-time. The usual way to do this is mounting a volume with your source code in the container that has the runtime of your application. But for production this works differently. Before you host your web application in production environment, you might want to turn-off the debug mode and host it under the right port so as to test your application usability and accessibility. In production you have a cluster with multiple nodes, and in most of the case volume is local to the node where your container (or service) is running, then you cannot mount the source code without complex stuff that involve code synchronization, signals, etc. In nutshell, this might require multiple Docker compose files for each environment and as your number of service applications increases, it becomes more cumbersome to manage those pieces of Compose files. Hence, we need a tool which can ease the way Compose files can be shareable across different environment seamlessly.
To solve this problem, Docker, Inc recently announced a new tool called “docker-app”(Application Packages) which makes “Compose files more reusable and shareable”. This tool not only makes Compose file shareable but provide us with simplified approach to share multi-service application (not just Docker Image) directly on Dockerhub.
Under this blog post, I will showcase how docker-app tool makes it easier to use Docker Compose for sharing and collaboration and then pushing it directly to DockerHub. Let us get started-
Prerequisite:
- Open https://labs.play-with-docker.com on your browser
- Click on Icon near to Instance to choose 3 Managers & 2 Worker Nodes
Deploy 5 Node Swarm Mode Cluster
$ docker node ls
ID HOSTNAME STATUS AVAILABILITY MANAGER STATUS ENGINE VERSION
juld0kwbajyn11gx3bon9bsct * manager1 Ready Active Leader 18.03.1-ce
uu675q2209xotom4vys0el5jw manager2 Ready Active Reachable 18.03.1-ce
05jewa2brfkvgzklpvlze01rr manager3 Ready Active Reachable 18.03.1-ce
n3frm1rv4gn93his3511llm6r worker1 Ready Active 18.03.1-ce
50vsx5nvwx5rbkxob2ua1c6dr worker2 Ready Active 18.03.1-ce
Cloning the Repository
$ git clone https://github.com/ajeetraina/app
Cloning into 'app'...remote: Counting objects: 14147, done.
remote: Total 14147 (delta 0), reused 0 (delta 0), pack-reused 14147Receiving objects: 100% (14147/14147), 17.32 MiB | 18.43 MiB/s, done.
Resolving deltas: 100% (5152/5152), done.
Installing docker-app
wget https://github.com/docker/app/releases/download/v0.3.0/docker-app-linux.tar.gz
tar xf docker-app-linux.tar.gz
cp docker-app-linux /usr/local/bin/docker-app
OR
$ ./install.sh
Connecting to github.com (192.30.253.112:443)
Connecting to github-production-release-asset-2e65be.s3.amazonaws.com (52.216.227.152:443)
docker-app-linux.tar 100% |**************************************************************| 8780k 0:00:00 ETA
[manager1] (local) root@192.168.0.13 ~/app
$
Verify docker-app version
$ docker-app version
Version: v0.3.0
Git commit: fba6a09
Built: Fri Jun 29 13:09:30 2018
OS/Arch: linux/amd64
Experimental: off
Renderers: none
The docker-app tool comes with various options as shown below:
$ docker-app
Build and deploy Docker applications.
Usage:
docker-app [command]
Available Commands:
deploy Deploy or update an application
helm Generate a Helm chart
help Help about any command
init Start building a Docker application
inspect Shows metadata and settings for a given application
ls List applications.
merge Merge the application as a single file multi-document YAML
push Push the application to a registry
render Render the Compose file for the application
save Save the application as an image to the docker daemon(in preparation for push)
split Split a single-file application into multiple files
version Print version information
Flags:
--debug Enable debug mode
-h, --help help for docker-app
Use "docker-app [command] --help" for more information about a command.
[manager1] (local) root@192.168.0.48 ~/app
WordPress Application under dev & Prod environment
If you browse to app/examples/wordpress directory under GitHub Repo, you will see that there is a folder called wordpress.dockerapp that contains three YAML documents:
- metadatas
- the Compose file
- settings for your application
Okay, Fine ! But how you created those files?
The docker-app tool comes with an option “init” which initialize any application with the above 3 YAML files and the directory structure can be initialized with the below command:
docker-app init --single-file wordpress
I have already created a directory structure for my environment and you can find few examples under this directory.
Listing the WordPress Application package related files/directories
$ ls
README.md install-wp with-secrets.yml
devel prod wordpress.dockerapp
As you see above, I have created each folder for my environment – dev and prod. Under these directories, I have created prod-settings.yml and dev-settings.yml. You can view the content via this link.
WordPress Application Package for Dev Environ
I can pass “-f” <YAML> parameter to docker-app tool to render the respective environment settings seamlessly as shown below:
$ docker-app render wordpress -f devel/dev-settings.yml
version: "3.6"
services:
mysql:
deploy:
mode: replicated
replicas: 1
endpoint_mode: dnsrr
environment:
MYSQL_DATABASE: wordpressdata
MYSQL_PASSWORD: wordpress
MYSQL_ROOT_PASSWORD: wordpress101
MYSQL_USER: wordpress
image: mysql:5.6
networks:
overlay: null
volumes:
- type: volume
source: db_data
target: /var/lib/mysql
wordpress:
depends_on:
- mysql
deploy:
mode: replicated
replicas: 1
endpoint_mode: vip
environment:
WORDPRESS_DB_HOST: mysql
WORDPRESS_DB_NAME: wordpressdata
WORDPRESS_DB_PASSWORD: wordpress
WORDPRESS_DB_USER: wordpress
WORDPRESS_DEBUG: "true"
image: wordpress
networks:
overlay: null
ports:
- mode: ingress
target: 80
published: 8082
protocol: tcp
networks:
overlay: {}
volumes:
db_data:
name: db_data
WordPress Application Package for Prod
Under Prod environment, I have the following content under prod/prod-settings.yml as shown :
debug: false
wordpress:
port: 80
For production environment, it is obvious that I want my application to be exposed under the standard port:80. Post rendering, you should be able to see port:80 exposed as shown below in the snippet:
image: wordpress
networks:
overlay: null
ports:
- mode: ingress
target: 80
published: 80
protocol: tcp
networks:
overlay: {}
volumes:
db_data:
name: db_dataInspect the WordPress App
$ docker-app inspect wordpress
wordpress 1.0.0
Maintained by: ajeetraina <ajeetraina@gmail.com>
Welcome to Collabnix
Setting Default
------- -------
debug true
mysql.database wordpressdata
mysql.image.version 5.6
mysql.rootpass wordpress101
mysql.scale.endpoint_mode dnsrr
mysql.scale.mode replicated
mysql.scale.replicas 1
mysql.user.name wordpress
mysql.user.password wordpress
volumes.db_data.name db_data
wordpress.port 8081
wordpress.scale.endpoint_mode vip
wordpress.scale.mode replicated
wordpress.scale.replicas 1
[manager1] (local) root@192.168.0.13 ~/app/examples/wordpress
$
Deploying the WordPress App
$ docker-app deploy wordpress
Creating network wordpress_overlay
Creating service wordpress_mysql
Creating service wordpress_wordpress
Switching to Dev Environ
If I want to switch back to Dev environment, all I need is to pass the dev specific YAML file using “-f” parameter as shown below:
$docker-app deploy wordpress -f devel/dev-settings.yml
Switching to Prod Environ
$docker-app deploy wordpress -f prod/prod-settings.yml
[manager1] (local) root@192.168.0.48 ~/app/examples/wordpress
$ docker-app deploy -f devel/dev-settings.yml
Updating service wordpress_wordpress (id: l95b4s6xi7q5mg7vj26lhzslb)
Updating service wordpress_mysql (id: lhr4h2uaer861zz1b04pst5sh)
[manager1] (local) root@192.168.0.48 ~/app/examples/wordpress
$ docker-app deploy -f prod/prod-settings.yml
Updating service wordpress_wordpress (id: l95b4s6xi7q5mg7vj26lhzslb)
Updating service wordpress_mysql (id: lhr4h2uaer861zz1b04pst5sh)
[manager1] (local) root@192.168.0.48 ~/app/examples/wordpress
$
Pushing Application Package to Dockerhub
So I have my application ready to be pushed to Dockerhub. Yes, you heard it right. I said, Application packages and NOT Docker Image.
Let me first authenticate myself before I push it to Dockerhub registry:
$ docker login
Login with your Docker ID to push and pull images from Docker Hub. If you don't have a Docker ID, head over to
https://hub.docker.com to create one.
Username: ajeetraina
Password:
Login Succeeded
[manager1] (local) root@192.168.0.48 ~/app/examples/wordpress
$
Saving this Application Package as Docker Image
The docker-app CLI is feature-rich and allows to save the entire application as a Docker Image. Let’s try it out –
[manager1] (local) root@192.168.0.48 ~/app/examples/wordpress
$ docker-app save wordpress
Saved application as image: wordpress.dockerapp:1.0.0
[manager1] (local) root@192.168.0.48 ~/app/examples/wordpress
$
Listing out the images
$ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
wordpress.dockerapp 1.0.0 c1ec4d18c16c 47 seconds ago 1.62kB
mysql 5.6 97fdbdd65c6a 3 days ago 256MB
[manager1] (local) root@192.168.0.48 ~/app/examples/wordpress
$
Listing out the services
$ docker stack services wordpress
ID NAME MODE REPLICAS IMAGE PORTS
l95b4s6xi7q5 wordpress_wordpress replicated 1/1 wordpress:latest *:80->80
/tcp
lhr4h2uaer86 wordpress_mysql replicated 1/1 mysql:5.6
[manager1] (local) root@192.168.0.48 ~/docker101/play-with-docker/visualizer
Using docker-app ls command to list out the application packages
The ‘ls’ command has been recently introduced under v0.3.0. Let us try it once –
$ docker-app ls
REPOSITORY TAG IMAGE ID CREATED SIZE
wordpress.dockerapp 1.0.1 299fb78857cb About a minute ago 1.62kB
wordpress.dockerapp 1.0.0 c1ec4d18c16c 16 minutes ago 1.62kB
Pusing it to Dockerhub
$ docker-app push --namespace ajeetraina --tag 1.0.1
The push refers to repository [docker.io/ajeetraina/wordpress.dockerapp]
51cfe2cfc2a8: Pushed
1.0.1: digest: sha256:14145fc6e743f09f92177a372b4a4851796ab6b8dc8fe49a0882fc5b5c1be4f9 size: 524
Say, you built WordPress application package and pushed it to Dockerhub. Now one of your colleague want to pull it on his development system and deploy in his environment.
Pulling it from Dockerhub
$ docker pull ajeetraina/wordpress.dockerapp:1.0.1
1.0.1: Pulling from ajeetraina/wordpress.dockerapp
a59931d48895: Pull complete
Digest: sha256:14145fc6e743f09f92177a372b4a4851796ab6b8dc8fe49a0882fc5b5c1be4f9
Status: Downloaded newer image for ajeetraina/wordpress.dockerapp:1.0.1
[manager3] (local) root@192.168.0.24 ~/app
$ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
ajeetraina/wordpress.dockerapp 1.0.1 299fb78857cb 8 minutes ago 1.62kB
[manager3] (local) root@192.168.0.24 ~/app
$
Deploying the Application
$ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
ajeetraina/wordpress.dockerapp 1.0.1 299fb78857cb 9 minutes ago 1.62kB
[manager3] (local) root@192.168.0.24 ~/app
$ docker-app deploy ajeetraina/wordpress
Creating network wordpress_overlay
Creating service wordpress_mysql
Creating service wordpress_wordpress
[manager3] (local) root@192.168.0.24 ~/app
$
Using docker-app merge option
Docker Team has introduced docker-app merge option under the new 0.3.0 release.
[manager1] (local) root@192.168.0.48 ~/app/examples/wordpress
$ docker-app merge -o mywordpress
[manager1] (local) root@192.168.0.48 ~/app/examples/wordpress
$ ls
README.md install-wp prod wordpress.dockerapp
devel mywordpress with-secrets.yml
$ cat mywordpress
version: 1.0.1
name: wordpress
description: "Welcome to Collabnix"
maintainers:
- name: ajeetraina
email: ajeetraina@gmail.com
targets:
swarm: true
kubernetes: true
--
version: "3.6"
services:
mysql:
image: mysql:${mysql.image.version}
environment:
MYSQL_ROOT_PASSWORD: ${mysql.rootpass}
MYSQL_DATABASE: ${mysql.database}
MYSQL_USER: ${mysql.user.name}
MYSQL_PASSWORD: ${mysql.user.password}
volumes:
- source: db_data
target: /var/lib/mysql
type: volume
networks:
- overlay
deploy:
mode: ${mysql.scale.mode}
replicas: ${mysql.scale.replicas}
endpoint_mode: ${mysql.scale.endpoint_mode}
wordpress:
image: wordpress
environment:
WORDPRESS_DB_USER: ${mysql.user.name}
WORDPRESS_DB_PASSWORD: ${mysql.user.password}
WORDPRESS_DB_NAME: ${mysql.database}
WORDPRESS_DB_HOST: mysql
WORDPRESS_DEBUG: ${debug}
ports:
- "${wordpress.port}:80"
networks:
- overlay
deploy:
mode: ${wordpress.scale.mode}
replicas: ${wordpress.scale.replicas}
endpoint_mode: ${wordpress.scale.endpoint_mode}
depends_on:
- mysql
volumes:
db_data:
name: ${volumes.db_data.name}
networks:
overlay:
--
debug: true
mysql:
image:
version: 5.6
rootpass: wordpress101
database: wordpressdata
user:
name: wordpress
password: wordpress
scale:
endpoint_mode: dnsrr
mode: replicated
replicas: 1
wordpress:
scale:
mode: replicated
replicas: 1
endpoint_mode: vip
port: 8081
volumes:
db_data:
name: db_datadocker-app comes with a few other helpful commands as well, in particular the ability to create Helm Charts from your Docker Applications. This can be useful if you’re adopting Kubernetes, and standardising on Helm to manage the lifecycle of your application components, but want to maintain the simplicity of Compose when writing you applications. This also makes it easy to run the same applications locally just using Docker, if you don’t want to be running a full Kubernetes cluster.
Did you find this blog helpful? Feel free to share your experience. Get in touch with me at twitter @ajeetsraina.
If you want to keep track of latest Docker related information, follow me at https://www.linkedin.com/in/ajeetsraina/.
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