Making Sense of LDK & LDK Node

I like to think about the architecture of software systems in a particular way, i.e. hexagonal architecture with clean separation between driving and driven ports, and with adaptable interfaces to make systems modular and components interchangeable. This note contains the representation of LDK in this style and captures what I have learned studying the development kit in the past few months.

Note: I am uncertain if this style applies in the way that I have used it but it has been helpful in organizing my thoughts about the layout and the direction of the flow of data.

Architectural Overview of LDK

LDK is composed of four major structures

• ChannelManager to handle off-chain channel management

• ChainMonitor to handle on-chain monitoring of relevant transactions

• PeerManager to manage peers, (dis)connecting to, and forwarding/receiving messages

• P2PGossipSync for the latest view of the network graph and the propagation of gossip across the network.

The architecture is requires careful management of state, is event-driven, having structures that can generate events and messages, and those with the tools to handle the generated events/messages.

ldk

LDK Node

LDK Node is the lightning node based on LDK, integrating the development kit and other pluggable/adaptable tools:

• block/transaction-sync: to sync channel and wallet operations, as well as fee rate estimation to the chain,

• invoice generation,

• persistence: to save channel state,

• networking,

• rapid gossip, and

• background processing.

Note: Red dotted lines showing how LDK Node integrates LDK.

ldk-node