README.md

Broadcast

Overview

This example shows how a party broadcaster can send data to subscribers. DAML's divulgence mechanism ensures that the broadcast data lands in subscribers' PCSs and can be used to submit transactions. This is an alternative to the use of observer. It lacks the guarantees of observer, but subscribers don't find out about each other, and the transaction size of adding a new subscriber doesn't grow with the number of subscribers.

Workflow

1. The broadcaster creates a Broadcast and BroadcastData which they want to broadcast.
2. Subscribers create SubscriptionRequest contracts to ask to be added to the Broadcast. The broadcaster accepts these via choice AcceptSubscription.
3. The broadcaster updates the Broadcast via the BroadcastUpdate choice on Broadcast.

Building

To compile the project:

daml build

Testing

The model is tested in scenario test_broadcast. Note how as subscribers are added, the BroadcastUpdate transactions get larger, but the transaction to add a new subscriber is constant size. To run all scenarios:

daml test --color

Running

To load the project into the sandbox and start navigator:

daml start