OpenDC Web Server
Collaborative Datacenter Simulation and Exploration for Everybody
The OpenDC web server is the bridge between OpenDC's frontend and database. It is built with Flask/SocketIO in Python and implements the OpenAPI-compliant [OpenDC API specification](../opendc-api-spec.yml).
This document explains a high-level view of the web server architecture ([jump](#architecture)), and describes how to set up the web server for local development ([jump](#setup-for-local-development)).
## Architecture
The following diagram shows a high-level view of the architecture of the OpenDC web server. Squared-off colored boxes indicate packages (colors become more saturated as packages are nested); rounded-off boxes indicate individual components; dotted lines indicate control flow; and solid lines indicate data flow.
The OpenDC API is implemented by the `Main Server Loop`, which is the only component in the base package.
### Util Package
The `Util` package handles several miscellaneous tasks:
* `Database API`: Wraps database access functionality used by `Models` to read themselves from/write themselves into the database.
* `Exceptions`: Holds definitions for exceptions used throughout the web server.
* `Parameter Checker`: Recursively checks whether required `Request` parameters are present and correctly typed.
* `REST`: Parses SocketIO and HTTP messages into `Request` objects, and calls the appropriate `API` endpoint to get a `Response` object to return to the `Main Server Loop`.
### API Package
The `API` package contains the logic for the HTTP methods in each API endpoint. Packages are structured to mirror the API: the code for the endpoint `GET api/projects`, for example, would be located at the `endpoint.py` inside the `projects` package (so at `api/projects/endpoint.py`).
An `endpoint.py` file contains methods for each HTTP method it supports, which takes a request as input (such as `def GET(request):`). Typically, such a method checks whether the parameters were passed correctly (using the `Parameter Checker`); fetches some model from the database; checks whether the data exists and is accessible by the user who made the request; possibly modifies this data and writes it back to the database; and returns a JSON representation of the model.
The `REST` component dynamically imports the appropriate method from the appropriate `endpoint`, according to request it receives, and executes it.
### Models Package
The `models` package contains the logic for mapping Python objects to their database representations. This involves an abstract `model` which has generic CRUD operations. Extensions of `model`, such as a `User` or `Project`, specify some more specific operations and their collection metadata.
`Endpoint`s import these `models` and use them to execute requests.
## Setup for Local Development
The following steps will guide you through setting up the OpenDC web server locally for development. To test individual endpoints, edit `static/index.html`.
### Local Setup
#### Install requirements
Make sure you have Python 3.7+ installed (if not, get it [here](https://www.python.org/)), as well as pip (if not, get it [here](https://pip.pypa.io/en/stable/installing/)). Then run the following to install the requirements.
```bash
pip install -r requirements.txt
```
The web server also requires a running MongoDB instance. We recommend setting this up through docker, by running `docker-compose build` and `docker-compose up` in the [`mongodb` directory](../database) of the main OpenDC repository.
#### Get and configure the code
Clone OpenDC and follow the [instructions in the main repository](../) to set up a Google OAuth ID and environment variables.
**Important:** Be sure to set up environment variables according to those instructions, in a `.env` file.
In `api/static/index.html`, add your own `OAUTH_CLIENT_ID` in `content=` on line `2`.
#### Set up the database
You can selectively run only the database services from the standard OpenDC `docker-compose` setup:
```bash
docker-compose build mongo mongo-express
docker-compose up mongo mongo-express
```
This will set you up with a running MongoDB instance and a visual inspection tool running on [localhost:8082](http://localhost:8082), with which you can view and manipulate the database.
### Local Development
Run the server.
```bash
cd api
python main.py
```
When editing the web server code, restart the server (`CTRL` + `c` followed by `python main.py` in the console running the server) to see the result of your changes.
#### Code Style
To format all files, run `format.sh` in this directory (uses `yapf` internally).
To check if code style is up to modern standards, run `check.sh` in this directory (uses `pylint` internally).
#### Testing
Run `pytest` in this directory to run all tests.