Application

A deroll App is responsible for the main loop of the Cartesi application. It fetches advance requests (inputs) sent to the application, handling them to advance handlers, and inspect requests to inspect handlers.

The source of these requests is usually the rollups HTTP server that runs inside the Cartesi Machine, which fetches requests from the outside using Cartesi I/O primitives.

You can construct an App that communicates with the rollups HTTP server using the createApp function. You must specify the URL of the HTTP server, which by default is set in the application Dockerfile as the environment variable ROLLUP_HTTP_SERVER_URL=http://127.0.0.1:5004.

import { createApp } from "@deroll/app";
 
// create application
const app = createApp({ url: "http://127.0.0.1:5004" }); 

You then call the app.start() method. That will enter in a continuous loop, fetching requests and handling them to the application request handlers.

import { createApp } from "@deroll/app";
 
// create application
const app = createApp({ url: "http://127.0.0.1:5004" });
 
// start app
app.start().catch((e) => process.exit(1)); 

In the example above we are catching exceptions and exiting the application. Keep in mind that exiting a Cartesi rollups application means that the rollups is terminated forever.

To do anything useful the application must implement AdvanceHandler's and InspectHandler's, which is the subject of the following sections.