This repository contains scripts for deploying the web-platform-tests project (WPT) to the web such that its tests can be run in a web browser. The deployment has been designed for stability and for relevancy (by automatically synchronizing with the latest revision of WPT).
The web-platform-tests server is known to be unreliable, so in order to offer a consistent experience, this project uses a non-trivial server layout in Google Cloud Platform.
*Let's Encrypt* *GitHub*
| |
[TLS certificate] [WPT source code]
| .------------. |
V .-->| wpt server |<---+
.--------------. +++++++++++++++ | '------------' |
| cert-renewer |--->+ certificate +---+ |
'--------------' + store + | .------------. |
+++++++++++++++ '-->| wpt server |<---'
'------------'
Legend
.---. +++++
* * external | | GCE + + object [ ] message
service '---' instance +++++ store contents
The server is run by multiple Google Compute Engine (or "GCE") instances deployed in parallel. These are members of a Managed Instance Group, so when one fails, it is automatically destroyed, and a new instance is created in its place. Many of the web-platform-tests concern the semantics of the HTTP protocol, so load balancing is provided at the TCP level in order to avoid interference.
In addition to serving the web-platform-tests, each server performs a few tasks on a regular interval. These include:
- fetching the latest revision of the web-platform-tests project from the canonical git repository hosted on GitHub.com
- fetching TLS certificates from the internally-managed object store (see below)
When any of these periodic tasks complete, the web-platform-tests server process is restarted in order to apply the changes.
A separate Google Compute Engine instance interfaces with the Let's Encrypt service to retrieve TLS certificates for the WPT servers. It integrates with Google Cloud Platform's DNS management in order to prove ownership of the system's domain name. It stores the certificates in a Google Cloud Platform Storage bucket for retrieval by the web-platform-tests servers.
Each server described above runs its application code in a Docker container. A single container does not provide any benefit in terms of isolation, but it does add value in two other ways:
- Ease of deployment. Contributors can build images, run them locally, and
publish them for use in the production environment. These operations have
been abstracted in the project's
Makefile. - Error recovery. In production, the containers are executed with the "always" restart policy. This ensures that if a sub-system fails, it is automatically revived from a consistent state.
Moreover, this project contradicts common practice of Docker-based development in that it runs multiple processes in a single container (managed by Supervisord). This further simplifies deployment because Google Compute Engine instances can be configured to run Docker containers, avoiding the complexity introduced by orchestration tools like Docker Compose or Kubernetes.
If the WPT server fails (as indicated by its process exiting), then Docker as running in the Google Compute Engine Instance will automatically restart the Docker container.
container GCE Instance
| |
x |
err!
.---restart---'
| |
| okay
Restarting the container completely refreshes runtime state, and this is expected to resolve many potential problems in the deployment.
In the case of the web-platform-tests server, an additional layer of error recovery is provided via a Google Cloud Platform "health check." If the Google Compute Engine instance fails to respond to HTTP requests, then it will be destroyed and a new one created in its place. That new instance will subsequently create a Docker container to run the WPT server.
container GCE Instance GCE Managed Group
| | |
x x |
err!
.-----restart-----'
| |
.---restart---' |
| | |
| okay |
| | |
| | okay
This second recovery mechanism guards against more persistent problems, e.g. those stemming from state on disk (since even a running GCE instance will fail HTTP health checks if restarting the Docker container has no effect).
Requirements:
The following commands will build Docker images for the respective sub-systems:
make cert-renewer
make wpt-server-tot
The following commands will build the Docker images and run them on the local system:
make run-cert-renewer
make run-wpt-server-tot
Running these containers requires the specification of a number of environment
variables. See the appropriate Dockerfile for a definition of the expected
variables.
Requirements:
The following commands will run the lints:
pipenv install --dev
pipenv run flake8
terraform fmt --check
Requirements:
- Docker
- GNU Make
- Terraform version 0.11.14
- Python 3
- access credentials to the Google Cloud Platform project, saved to a file named
google-cloud-platform-credentials.jsonin the root pf this repository
The following commands will build Docker images for the respective sub-systems and upload them to Google Cloud Platform:
make publish-cert-renewer
make publish-wpt-server-tot
Publishing new images will not directly affect the deployed system. In order to deploy new images, the GCP managed instance groups must be updated using Terraform.
The following command will synchronize the infrastructure running in Google Cloud Platform with the state described by the configuration files in this repository:
terraform apply