Fluid Ledger DDS

Ledger is a simple append-only list distributed data structure (DDS) for Fluid Framework.

Clients submit appends to the DDS but the underlying list gets update only after the op has been sequenced by the service. This ensures all clients end up with the same ordering of objects in the list.

The DDS provides an append event which fires whenever a new item is appended to the list and a clear event with fires whenever a client calls clear(). append will include the value appended, clear will have a copy of the ledger values that were cleared. Listeners can use these to react to changes.

The DDS provides a get() method which returns an iterable iterator over the underlying list, an append() method which submits a new item to be appended to the list, and a clear() method which clears the list. Client shouldn't assume the data is immediately appended (or cleared), rather wait for the events (other append or clear operations incoming from other clients might be interleaved).

Getting started

Install:

npm install fluid-ledger-dds

Set up and use a Ledger:

import { Ledger } from "fluid-ledger-dds";

let ledger: Ledger<number> = ...

ledger.on("append", (value) => {
  console.log(`New value appended to ledger: ${value}`);
});

ledger.on("clear", (values) => {
  console.log(`Ledger was cleared. It contained: ${values}`);
});

// Append a value to the ledger
ledger.append(42);

for (const value of ledger.get()) {
  // Iterate over existing values
}

// Clear ledger
ledger.clear();