109 lines
4.3 KiB
Markdown
109 lines
4.3 KiB
Markdown
# Capella -- Honest Validator
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**Notice**: This document is a work-in-progress for researchers and implementers.
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## Table of contents
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<!-- TOC -->
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<!-- START doctoc generated TOC please keep comment here to allow auto update -->
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<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
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- [Introduction](#introduction)
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- [Prerequisites](#prerequisites)
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- [Helpers](#helpers)
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- [Protocols](#protocols)
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- [`ExecutionEngine`](#executionengine)
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- [`get_payload`](#get_payload)
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- [Beacon chain responsibilities](#beacon-chain-responsibilities)
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- [Block proposal](#block-proposal)
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- [Constructing the `BeaconBlockBody`](#constructing-the-beaconblockbody)
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- [ExecutionPayload](#executionpayload)
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<!-- END doctoc generated TOC please keep comment here to allow auto update -->
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<!-- /TOC -->
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## Introduction
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This document represents the changes to be made in the code of an "honest validator" to implement the Capella upgrade.
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## Prerequisites
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This document is an extension of the [Bellatrix -- Honest Validator](../bellatrix/validator.md) guide.
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All behaviors and definitions defined in this document, and documents it extends, carry over unless explicitly noted or overridden.
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All terminology, constants, functions, and protocol mechanics defined in the updated Beacon Chain doc of [Capella](./beacon-chain.md) are requisite for this document and used throughout.
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Please see related Beacon Chain doc before continuing and use them as a reference throughout.
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## Helpers
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## Protocols
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### `ExecutionEngine`
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#### `get_payload`
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`get_payload` returns the upgraded Capella `ExecutionPayload` type.
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## Beacon chain responsibilities
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All validator responsibilities remain unchanged other than those noted below.
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### Block proposal
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#### Constructing the `BeaconBlockBody`
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##### ExecutionPayload
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`ExecutionPayload`s are constructed as they were in Bellatrix, except that the
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expected withdrawals for the slot must be gathered from the `state` (utilizing the
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helper `get_expected_withdrawals`) and passed into the `ExecutionEngine` within `prepare_execution_payload`.
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```python
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def get_expected_withdrawals(state: BeaconState) -> Sequence[Withdrawal]:
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num_withdrawals = min(MAX_WITHDRAWALS_PER_PAYLOAD, len(state.withdrawal_queue))
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return state.withdrawal_queue[:num_withdrawals]
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```
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*Note*: The only change made to `prepare_execution_payload` is to call
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`get_expected_withdrawals()` to set the new `withdrawals` field of `PayloadAttributes`.
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```python
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def prepare_execution_payload(state: BeaconState,
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pow_chain: Dict[Hash32, PowBlock],
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safe_block_hash: Hash32,
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finalized_block_hash: Hash32,
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suggested_fee_recipient: ExecutionAddress,
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execution_engine: ExecutionEngine) -> Optional[PayloadId]:
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if not is_merge_transition_complete(state):
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is_terminal_block_hash_set = TERMINAL_BLOCK_HASH != Hash32()
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is_activation_epoch_reached = get_current_epoch(state) >= TERMINAL_BLOCK_HASH_ACTIVATION_EPOCH
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if is_terminal_block_hash_set and not is_activation_epoch_reached:
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# Terminal block hash is set but activation epoch is not yet reached, no prepare payload call is needed
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return None
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terminal_pow_block = get_terminal_pow_block(pow_chain)
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if terminal_pow_block is None:
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# Pre-merge, no prepare payload call is needed
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return None
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# Signify merge via producing on top of the terminal PoW block
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parent_hash = terminal_pow_block.block_hash
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else:
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# Post-merge, normal payload
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parent_hash = state.latest_execution_payload_header.block_hash
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# Set the forkchoice head and initiate the payload build process
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payload_attributes = PayloadAttributes(
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timestamp=compute_timestamp_at_slot(state, state.slot),
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prev_randao=get_randao_mix(state, get_current_epoch(state)),
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suggested_fee_recipient=suggested_fee_recipient,
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withdrawals=get_expected_withdrawals(state), # [New in Capella]
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)
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return execution_engine.notify_forkchoice_updated(
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head_block_hash=parent_hash,
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safe_block_hash=safe_block_hash,
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finalized_block_hash=finalized_block_hash,
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payload_attributes=payload_attributes,
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)
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```
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