Divio Cloud overview¶
The Divio Cloud is a Docker-based platform-as-a-service. See Docker basics for an introduction to Docker and its key components.
The Divio Cloud offers a local development environment that replicates almost perfectly the Cloud environments in which applications run, eliminating many of the pain-points of deployment caused by having to deal with different environments in development and production.
In our architecture, we abstract functionality from configuration so that functional components can be made immutable and stateless wherever possible. This enables them to be replaced, added, moved and so on simply by spinning up new instances, without requiring manual configuration.
Divio Cloud infrastructure¶
Our Cloud is built on a Python/Django stack. Our client sites run in Docker containers. More information about our infrastructure can be provided on request.
Divio Cloud projects¶
The three environments¶
Each Divio Cloud project includes three environments, each of which will create a version of the website.
The three environments are created in Docker containers from the same images.
- Local, running on your own computer
- Test, running on our Cloud servers
- Live, running on our Cloud servers
In our workflow, development is done locally, before being deployed to Test and finally to Live.
Default project conditions¶
Some of these conditions may be easily altered according your needs, for example the DEBUG
setting. See also How to run a local project in live configuration.
| Local | Test | Live | |
|---|---|---|---|
STAGE environment variable |
local |
test |
live |
DEBUG environment variable |
True |
True |
False |
| static files served by | Python runserver | uWSGI | |
| media files served by | our Cloud S3 service | ||
| database runs in | a local container | our Cloud database cluster | |
| number of application containers | one | according to subscription | |
| application container sleeps | n/a | after 15 minutes’ activity | never |
Project site stack¶
The stack running Cloud sites is:
- Container
- Docker
- Operating system
- Ubuntu Linux
- Web server/web application gateway
- Divio loadbalancer plus uWSGI (local sites use the Django runserver.)
- Database
- Postgres (Test and Live sites use an AWS database; Local sites use a database running in another local container.)
- Applications
- Python/Django
Project repository branches¶
By default, each project’s code is in its Git develop branch. This is then
pushed to our Git server, where it can be deployed to the Test or Live servers
(our strongly -recommended workflow is always to deploy to Test first),
However, on request different branches can be set for the Test and Live servers - for example, develop and master respectively.
In this workflow you would work on develop before manually merging into
master, and then deploying Live.
Boilerplates¶
Divio Cloud projects represent web projects. Each project requires a frontend,
however minimal - at the very least, a basic base.html template. In order
to make Divio Cloud projects immediately useful, they each come with frontend
files included. These are defined by the site’s Boilerplate, a set of default templates and static file.
Typically, a Boilerplate will define how the Django templates are structured and make opinionated choices about what JavaScript frameworks and CSS tools are used.
Various Boilerplates are provided as defaults, but it’s also possible to define and reuse your own.
Our simplest Boilerplates provide only basic HTML and CSS, but more sophisticated ones include advanced frontend tooling: NPM, webpack, Sass and other components.
Docker on Divio Cloud¶
Docker layer caching¶
We don’t use Docker-level layer caching, as certain cases can produce unexpected results:
- Unpinned installation commands might install cached versions of software, even where the user expects a newer version.
- Commands such as
apt-get upgradein a Dockerfile could similarly fail to pick up new changes. - Our clustered setup means that builds take place on different hosts. As Docker layer caching is local to each host, this could mean that subsequent builds use different versions, depending on what is in each host’s cache.