PR Review Club: feat: Make MonitorUpdatingPersister change persist type based on size

[Prabhat1308]

Rust-Lightning PR Review Club

Session Details

• Date: 17/07/2025
• Time: IST 19:00 (UTC 13:30)
• Title: feat: Make MonitorUpdatingPersister change persist type based on size
• PR: feat: Make MonitorUpdatingPersister change persist type based on size lightningdevkit/rust-lightning#3834

PR Summary

Small ldk-nodes might not want to use update-based persistence when Monitor sizes are small . This is because of more load of mapping updates files and check for differential updates which are not really beneficial for smaller nodes . This adds a tunable option to the nodes where they can specify a threshold after which they would like to use update based persistence.

Prerequisites

rust

Questions

1. What is a MUP ?
2. why would we like to need persistence for our nodes ?
3. why would we prefer full monitor persistence over update based persistence in smaller nodes ?
4. What should be the ideal threshold value ?
5. Where in the code is persistence switched based on the threshold value ?

Preparation Steps

1. Clone the Bitcoin Core repository if you haven't already:

   git clone https://github.com/lightningdevkit/rust-lightning
   

2. Fetch and checkout the PR:

   cd bitcoin
   git fetch origin pull/3834/head:Prabhat1308:probot/change_persist_type
   git checkout Prabhat1308:probot/change_persist_type
   

3. Review the code changes and consider the provided questions.

Joining the Session

The Jitsi link will be shared in the #announcements channel of the Bitshala Discord shortly before the session.

Looking forward to seeing you there!