April 19, 2020
Kernel pos index
One necessary piece of technical implementation required by the “No Recent Duplicate” NRD proposal is a local db index tracking kernel MMR pos for each NRD kernel encountered. This index needs to support multiple entries indexed by the kernel excess commitment.
Majority of my time last week was focused on this.
We had an existing WIP PR that was experimenting with a “linked list” implementation for the output pos index. This has now been repurposed and iterated on to focus on the kernel pos index.
- Old PR - https://github.com/mimblewimble/grin/pull/3273
- New PR - https://github.com/mimblewimble/grin/pull/3302
The index currently supports coinbase kernels as proof of concept (we need a single kernel feature to index). Once NRD kernels exist we can rework this to be NRD kernel specific.
Currently support applying new kernels as part of processing a block and “rewinding” the index to support fork/reorg.
TODO - The index does not currently prune/compact historical data. Next step is likely to add functionality here to maintai the index only for recent data by pruning old data during chain compaction.
PayJoin
Also took an unrelated detour last week to investigate PayJoin which seems to be suddenly getting a lot of attention over in the Bitcoin ecosystem.
I wrote some early thoughts up here - PayJoin (P2EP) in Grin