Databases with dokku
This is part 2 of a couple of blog posts about dokku, a amazing little Heroku clone.
In the previous post I showed how to set up Dokku on a DigitalOcean droplet, and deployed a little hello-world container with a single git push. The reason why I wanted dokku thoug was the need of a database. As said – hosting comes cheap, databases usually come either expensive or with limited flexibility, or just too annoying configuration effort.
Dokku is the perferct middle ground. Let’s see why.
For me it was the existing postgres plugin which you can simply install and use. The whole process is incredibly easy, takes wbout two commands, and looks like this (let’s assume our “hello world” container uses a database):
$ sudo dokku plugin:install https://github.com/dokku/dokku-postgres.git postgres
That’s it, again.
$ dokku postgres:create hello-world
dokku postgres:create hello-world
Waiting for container to be ready
Creating container database Securing connection to database
=====> Postgres container created: hello-world
=====> Container Information
Config dir: /var/lib/dokku/services/postgres/hello-world/config
Data dir: /var/lib/dokku/services/postgres/hello-world/data
Dsn: postgres://postgres:bd6b0725d710bb5a662bb628eee787b1@dokku-postgres-hello-world:5432/hello_world
Exposed ports: -
Id: 785ef252c748ed85739d1d6ad375a1e1bd66e925ac79358e9ffaa30ab852d6c0
Internal ip: 172.17.0.9
Links: -
Service root: /var/lib/dokku/services/postgres/hello-world
Status: running
Version: postgres:10.2
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
cc99cccacf2c dokku/hello-world:latest "/bin/sh -c 'php-fpm…" 2 minutes ago Up 2 minutes 80/tcp hello-world.web.1
785ef252c748 postgres:10.2 "docker-entrypoint.s…" 5 minutes ago Up 5 minutes 5432/tcp dokku.postgres.hello-world
[...]
This creates a database container with postgres 10.2, as you can see. You can influence a lot of behavior by using environment variables, see the GitHub page for more info.
Then you link the container to the running app:
$ dokku postgres:link hello-world hello-world
-----> Setting config vars
DATABASE_URL: postgres://postgres:bd6b0725d710bb5a662bb628eee787b1@dokku-postgres-hello-world:5432/hello_world
-----> Restarting app hello-world
-----> Releasing hello-world (dokku/hello-world:latest)...
-----> Deploying hello-world (dokku/hello-world:latest)...
-----> Attempting to run scripts.dokku.predeploy from app.json (if defined)
-----> No Procfile found in app image
-----> DOKKU_SCALE file found (/home/dokku/hello-world/DOKKU_SCALE)
=====> web=1
-----> Attempting pre-flight checks
For more efficient zero downtime deployments, create a file CHECKS.
See http://dokku.viewdocs.io/dokku/deployment/zero-downtime-deploys/ for examples
CHECKS file not found in container: Running simple container check...
-----> Waiting for 10 seconds ...
-----> Default container check successful!
-----> Running post-deploy
-----> Configuring hello-world.my-paas.for-myself.com...(using built-in template)
-----> Creating http nginx.conf
-----> Running nginx-pre-reload Reloading nginx
-----> Setting config vars DOKKU_APP_RESTORE: 1
-----> Found previous container(s) (14c349cb496d) named hello-world.web.1
=====> Renaming container (14c349cb496d) hello-world.web.1 to hello-world.web.1.1535285386
=====> Renaming container (cc99cccacf2c) serene_bassi to hello-world.web.1
-----> Attempting to run scripts.dokku.postdeploy from app.json (if defined)
-----> Shutting down old containers in 60 seconds
=====> 14c349cb496d95cc4be1833f2e7f6ef2bef099a37c2a22cd4dcdb542f09bea0f
=====> Application deployed:
http://hello-world.my-paas.for-myself.com
And done.
What happened? You have now the environment variable $DATABASE_URL set in the hello-world app, that’s why the restart was necessary (which you can postpone, if you want, but you probably need it now, right?).
Let’s check:
$ docker exec -ti hello-world.web.1 /bin/sh [now in the container] # env | grep DATABASE DATABASE_URL=postgres://postgres:bd6b0725d710bb5a662bb628eee787b1@dokku-postgres-hello-world:5432/hello_world
That’s it. Super easy. Now if you’re using Django, you could use kennethreitz/dj-database-url to automatically parse and use it, and you’re done. (Probably every framework has something similar, so just have a look).
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