25.8 Migrating PEcAn from VM to Docker

This document assumes you have read through the Introduction to Docker as well as Docker quickstart and have docker running on the VM.

This document will slowly replace each of the components with the appropriate docker images. At then end of this document you should be able to use the docker-compose command to bring up the full docker stack as if you had started with this origianally.

25.8.1 Running BETY as a docker container

This will replace the BETY application running on the machine with a docker image. This will assume you still have the database running on the local machine and the only thing we replace is the BETY application.

If you are running systemd (Ubuntu 16.04 or Centos 7) you can copy the following file to /etc/systemd/system/bety.service (replace LOCAL_SERVER=99 with your actual server). If you have postgres running on another server replace 127.0.0.1 with the actual ip address of the postgres server.

[Unit]
Description=BETY container
After=docker.service

[Service]
Restart=always
ExecStart=/usr/bin/docker run -t --rm --name bety --add-host=postgres:127.0.0.1 --network=host --env RAILS_RELATIVE_URL_ROOT=/bety --env LOCAL_SERVER=99 pecan/bety
ExecStop=/usr/bin/docker stop -t 2 bety

[Install]
WantedBy=local.target

At this point we can enable the bety service (this only needs to be done once). First we need to tell systemd a new service is available using systemctl daemon-reload. Next we enable the BETY service so it will restart automatically when the machine reboots, using systemctl enable bety. Finally we can start the BETY service using systemctl start bety. At this point BETY is running as a docker container on port 8000. You can see the log messages using journalctl -u bety.

Next we need to modify apache configuration files. The file /etc/apache2/conf-enabled/bety.conf will be replaced with the following content:

ProxyPass                /bety/ http://pecan.localhost/bety/
ProxyPassReverse         /bety/ http://pecan.localhost/bety/
RedirectMatch permanent ^/bety$ /bety/

Once this modified we can restart apache using systemctl restart apache2. At this point BETY is running in a container and is accessable trough the webserver at http://server/bety/.

To upgrade to a new version of BETY you can now use the docker commands. You can use the following commands to stop BETY, pull the latest image down, migrate the database (you made a backup correct?) and start BETY again.

systemctl stop bety
docker pull pecan/bety:latest
docker run -ti --rm --add-host=postgres:127.0.0.1 --network=host --env LOCAL_SERVER=99 pecan/bety migrate
systemctl start bety

Once you are satisfied with the migration of BETY you can remove the bety folder as well as any ruby binaries you have installed.