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Jenzo

Generate meta images for your web pages on the fly with HTML templates.

Requirements

Jenzo will run on a lot of machines either using Docker or Node, but you might want/need to have these installed depending on how you want to run it:

  • Chromium (the Docker file already includes this)
  • Node (if you are not using Docker)
  • Docker (if you want to run it via Docker; recommended)

Running Jenzo

Running locally

You can run Jenzo locally on your machine by running the following commands:

yarn install
PORT=8080 yarn dev

By default, Jenzo will run on port 80, you can either pass in the PORT like this or include it in your ENV file, check the .env.example for supported environment variables.

Running in Docker

You can simply use the included docker-compose file to start with Docker compose:

docker compose up

Or you can build the image and run it

docker build -t jenzo .
docker run -it jenzo

Environment

NODE_ENV: this specifies the environment you are running in, this is very important as it also tells Puppeteer where to find your Chromium installation.

PORT: specifies the port you want Jenzo to run on

ADDR: specifies the address you want Jenzo to run on, this is usually just localhost or 127.0.0.1, but the default is 0.0.0.0 for Docker support.

CACHE_TTL: specifies how long you want images to be cached in minutes (recommended is 3 if you are more likely to be updating templates often) - the cache drastically reduces response time, but it could also result in getting stale data after updating a template if you set it too high.

ALLOWED_HOSTS: comma-separated host URLs you want to allow requests from (enforced via CORS)

VERSION: this is just used to determine the API endpoint (api/v(version), eg. api/v1)

Variables

Jenzo allows you to pass variables to your templates dynamically in the query parameter. Variables are defined in the following format:

vars=key:value

Templating (with example)

Jenzo allows you to combine variants (HTML) with styles (CSS) in any way you want; as long as you have predefined them, and use variables in those combined templates.

Here is a sample URL including variables (name, title and fontsize), a variant (HTML), a style (CSS) and a size (this takes small, medium or large):

http://localhost/api/v1/images/mono/preview?vars=name:John+Doe,title:Preview+Image,fontsize:3rem&size=small

Here is an example in Javascript using the qs library:

const query = qs.stringify({
  variant: "blog",
  style: "blog",
  vars: `title:${title},date:${date}`,
});
const metaUrl = `https://mysite.com/api/v1/images/mysite/preview?${query}`;

The POST requests used to manage the templates are protected with an API key you set (you will get a warning on startup if you set none) and, can be found in the swagger documentation at /docs and templates can be changed on the fly (again, be careful with the CACHE_TTL you have set).