[WIP] Stream best blocks to the relay instead of pushing them

[SkandaBhat]

📝 Summary

1. Use a block store that keeps track of the single best block at all times and streams it to any subscriber: https://github.com/SkandaBhat/rbuilder/blob/82f3d829ad4e9787847c66cb9cc157d22bad57dc/crates/rbuilder/src/building/builders/best_block_store.rs. Also added tests for both the store and tracker.

2. added a helper function on Block that helps keep the comparing logic more readable: https://github.com/flashbots/rbuilder/compare/develop...SkandaBhat:best-block-store?expand=1#diff-3349e9f2b5d24a3da06ac[…]1334cc81518f9090a131c9dR47. This is used in best_block_store

3. In relay_submit, we now subscribe to best_block_store and process best blocks as and when they arrive. BlockBuildingSink and BlockBuildingSinkFactory is not needed anymore here and we now call RelayCoordinator: https://github.com/flashbots/rbuilder/compare/develop...SkandaBhat:best-block-store?expand=1#diff-1ab827716722c4d9c2be8[…]19983e2a53a4c54b2553bf3cf0

4. In bid maker, we call try_and_update on the tracker, which checks if the block is better than the global best block, and if so, updates it on the global best block store: https://github.com/flashbots/rbuilder/compare/develop...SkandaBhat:best-block-store?expand=1#diff-be9eab4716937ef12a623[…]dfb88b7571d7f82e54c23eR131

5. UnfinishedBlockBuildingSink and UnfinishedBlockBuildingSinkFactory can be decoupled from BlockSealingBidder and the Sink can be entirely removed in favour of the new architecture, making the end to end process simpler.

💡 Motivation and Context

We have a push-based architecture for block building right now, where each builder runs a building algorithm and pushes blocks to a Sink, which sorts the blocks and submits the best block in a loop. This causes unnecessary flooding of the sink with low value blocks and additional overhead for the sink to sort every block it receives.

We can instead have a global best block store that stores a single best block at all times, and stream updates to any subscriber. This way, the relay sink can react immediately to updates from the store, and the builders can push best blocks only when they have a block that has a higher bid value than the global best block, thereby keeping the channel only for new best blocks found.

Overview

1. Builders report strictly best blocks to a Global Best Block Store
2. The sink subscribes to the Global Best Block Store
3. The sink processes updates(new blocks) to the Global Best Block Store on-demand
4. Builders subscribe to the Global Best Block Store and stores new best blocks whenever they arrive

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✅ I have completed the following steps:

• Run make lint
• Run make test
• Added tests (if applicable)

[github-actions]

Benchmark results for 6446e08

Report: https://flashbots-rbuilder-ci-stats.s3.us-east-2.amazonaws.com/benchmark/6446e08-16290b6/report/index.html

Date (UTC)	2024-12-13T09:57:25+00:00
Commit	6446e089e874beaeea353f1838d545f9bea4388a
Base SHA	16290b62a7b1a7693b04589ce403013bee09b20b

Significant changes

Benchmark	Mean	Status
MEV-Boost SubmitBlock serialization/JSON encoding	-35.40%	Performance has improved.