Builders & Sequencers
Block Building Package
To simplify the integration process for builders to support and fulfill the proposer’s commitments, we will provide a modified version of rbuilder, a blazingly fast MEV-Boost Rust-based block builder developed by Flashbots. Since rbuilder can handle several block building algorithms, our primary focus will be on updating the mev_boost/mod.rs and builders/ordering_builder.rs files. The changes will achieve 3 goals:
Stream the latest preconf transactions from the ETHGas exchange
Build a block that includes all preconf transactions of a specific slot
Fill up the block with transactions from the mempool if the gas used is below 30 million
Please refer to links below for modified rbuilder
[Link to Github, coming soon ]
Who Builds the Blocks?
Traders that are Whole Block owners may choose to Build/Sequence the block themselves, or delegate this to someone else: Specialist Builders, or the Fallback Builder. They may also elect for the Block to include no trades.
Self Building: Whole Block Owners as Sequencer/Builders
Traders who own the whole block are entitled to sequencing rights, conditional upon including the previously confirmed constraints/commitments. At expiry (t=0), traders build the block including their trades, and sequencing all the trades accordingly. They then send the block via our Relay upon which it then follows the standard PBS flow.
Delegated Building
Unlike Self Building above, where the Block Owner is also the Builder, traders will may elect to delegate the building to a 3rd party. This 3rd party may be either a Specialist Builder, or the Fallback Builder.
Prior to both delegation , traders must submit their transactions via API (subject to the amount of blockspace they own) so that the Builders know which trades to include accordingly.
Specialist Builders
Traders may delegate Building to a 3rd party Specialist or Dedicated Builder. Specialist Builders may or may not pass on priority fees or any other economics back to the Trader. This is at the Specialist Builder's discretion. [ More details shortly ]
Fallback Builder - ETHGas
ETHGas will perform the role as a Fallback Builder and sequence the block accordingly when:
The Block has not been Self Built, or
The Block has not been delegated to a 3rd party Specialist Builder, or
The Block built by the Builder does not conform to the commitment requirements,
Any priority fees from trades included in the block will pass back to the Block owner. More on the fallback sequencing algorithm in due course.
Non-Building
The Fallback Builder flow assumes that Traders will always want a block to be built with any residual value (i.e. remaining Tips/Priority fees from mempool transactions) being passed back to the Trader. There may be cases, albeit rare, where the Trader has sold no commitments and elects for no trades to be included. In these cases, traders must send an API request to this effect so that the Fallback Building process is not triggered.
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