Evora

Andor wrapper for Evora and Flask server.

Installation

evora-server requires the proprietary Andor libraries to be installed in /usr/local/lib. The library can be used for debugging without the Andor libraries, but they are necessary to run the actual camera.

To install evora-server, clone the repository and run

pip install .

or to install in editable mode

pip install -e .

Running the server

To run the server, from a terminal at the root of the project, execute

python app.py

which is equivalent to

flask --debug run --port 3000

Running in debug mode

To run the server in debug mode, with the dummy module mocking the camera, edit debug.py and set DEBUGGING = True.

Images

evora-server will save camera files to /data/ecam/DATE where DATE is in the format 20230504 and rotates at midnight UTC.

If /data/ecam does not exist, create it with mkdir -p and make sure it has the right permissions for evora-server to write to it.

Deploying for production

The recommended way to deploy evora-server is behind a gunicorn web server. To run the Flask webapp from gunicorn, execute

gunicorn -w 1 'app:app'

which will spin a web server with one worker. Currently the app is limited to run with one single worker since the connection to the camera cannot be shared.

To run this command in the background as a systemd service, create a file /etc/systemd/system/evora-server.service with the contents

[Unit]
Description=evora-server

[Service]
WorkingDirectory=/home/mrouser/Github/evora-server
ExecStart=/home/mrouser/Github/evora-server/gunicorn-start.sh

[Install]
WantedBy=multi-user.target

Here we are pointing to the file gunicorn-start.sh in the repo, which loads the conda environment and starts gunicorn. This may need to be changed for a location other than MRO. Then start the systemd service with

sudo systemctl daemon-reload
sudo systemctl enable --now enable evora-server
sudo systemctl restart evora-server

Configuring nginx

In addition to gunicorn, a reverse proxy is needed to run the Evora client and server in the same web server. In Ubuntu, install nginx (alternatively you can use Apache) with

sudo apt update
sudo apt install nginx

and adjust the firewall to open the desired ports. Then start nginx with

sudo systemctl enable --now nginx

We'll now add a new site for Evora. Create a new file /etc/nginx/sites-enabled/evora.conf with

sudo vim /etc/nginx/sites-enabled/evora.conf

and include the configuration

server {
    listen 80;
    listen [::]:80;
    server_name localhost;
    access_log  /usr/local/var/log/nginx/evora.log;

    location /api/ {
        proxy_pass http://127.0.0.1:8000/;
        proxy_set_header Host $host;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_connect_timeout 75s;
        proxy_read_timeout 1800s;
    }

    location /data {
       alias /data;
        autoindex on;
        index index.html index.php;
    }
}

This configuration creates a server running on port 80 (the default HTTP) and adds a reverse proxy to where gunicorn is running the Flask webapp. Note that we allow requests to the API to take as much as 30 minutes (which should be enough for most exposure times). It also creates a route to expose and browse /data.

After this, restart nginx with

sudo systemctl restart nginx

and test that it works by navigating to http://localhost/api/getTemperature.

References

Andor SDK documentation

siyu6974/evora-server