136 lines
4.8 KiB
Markdown
136 lines
4.8 KiB
Markdown
# Capella -- Fork Logic
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## Table of contents
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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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- [Configuration](#configuration)
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- [Helper functions](#helper-functions)
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- [Misc](#misc)
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- [Modified `compute_fork_version`](#modified-compute_fork_version)
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- [Fork to Capella](#fork-to-capella)
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- [Fork trigger](#fork-trigger)
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- [Upgrading the state](#upgrading-the-state)
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<!-- END doctoc generated TOC please keep comment here to allow auto update -->
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## Introduction
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This document describes the process of the Capella upgrade.
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## Configuration
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Warning: this configuration is not definitive.
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| Name | Value |
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| - | - |
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| `CAPELLA_FORK_VERSION` | `Version('0x03000000')` |
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| `CAPELLA_FORK_EPOCH` | `Epoch(18446744073709551615)` **TBD** |
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## Helper functions
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### Misc
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#### Modified `compute_fork_version`
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```python
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def compute_fork_version(epoch: Epoch) -> Version:
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"""
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Return the fork version at the given ``epoch``.
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"""
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if epoch >= CAPELLA_FORK_EPOCH:
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return CAPELLA_FORK_VERSION
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if epoch >= BELLATRIX_FORK_EPOCH:
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return BELLATRIX_FORK_VERSION
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if epoch >= ALTAIR_FORK_EPOCH:
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return ALTAIR_FORK_VERSION
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return GENESIS_FORK_VERSION
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```
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## Fork to Capella
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### Fork trigger
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The fork is triggered at epoch `CAPELLA_FORK_EPOCH`.
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Note that for the pure Capella networks, we don't apply `upgrade_to_capella` since it starts with Capella version logic.
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### Upgrading the state
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If `state.slot % SLOTS_PER_EPOCH == 0` and `compute_epoch_at_slot(state.slot) == CAPELLA_FORK_EPOCH`,
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an irregular state change is made to upgrade to Capella.
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The upgrade occurs after the completion of the inner loop of `process_slots` that sets `state.slot` equal to `CAPELLA_FORK_EPOCH * SLOTS_PER_EPOCH`.
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Care must be taken when transitioning through the fork boundary as implementations will need a modified [state transition function](../phase0/beacon-chain.md#beacon-chain-state-transition-function) that deviates from the Phase 0 document.
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In particular, the outer `state_transition` function defined in the Phase 0 document will not expose the precise fork slot to execute the upgrade in the presence of skipped slots at the fork boundary. Instead the logic must be within `process_slots`.
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```python
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def upgrade_to_capella(pre: bellatrix.BeaconState) -> BeaconState:
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epoch = bellatrix.get_current_epoch(pre)
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post = BeaconState(
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# Versioning
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genesis_time=pre.genesis_time,
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genesis_validators_root=pre.genesis_validators_root,
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slot=pre.slot,
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fork=Fork(
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previous_version=pre.fork.current_version,
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current_version=CAPELLA_FORK_VERSION,
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epoch=epoch,
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),
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# History
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latest_block_header=pre.latest_block_header,
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block_roots=pre.block_roots,
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state_roots=pre.state_roots,
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historical_roots=pre.historical_roots,
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# Eth1
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eth1_data=pre.eth1_data,
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eth1_data_votes=pre.eth1_data_votes,
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eth1_deposit_index=pre.eth1_deposit_index,
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# Registry
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validators=[],
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balances=pre.balances,
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# Randomness
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randao_mixes=pre.randao_mixes,
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# Slashings
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slashings=pre.slashings,
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# Participation
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previous_epoch_participation=pre.previous_epoch_participation,
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current_epoch_participation=pre.current_epoch_participation,
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# Finality
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justification_bits=pre.justification_bits,
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previous_justified_checkpoint=pre.previous_justified_checkpoint,
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current_justified_checkpoint=pre.current_justified_checkpoint,
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finalized_checkpoint=pre.finalized_checkpoint,
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# Inactivity
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inactivity_scores=pre.inactivity_scores,
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# Sync
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current_sync_committee=pre.current_sync_committee,
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next_sync_committee=pre.next_sync_committee,
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# Execution-layer
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latest_execution_payload_header=pre.latest_execution_payload_header,
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# Withdrawals
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withdrawal_queue=[],
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next_withdrawal_index=WithdrawalIndex(0),
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next_partial_withdrawal_validator_index=ValidatorIndex(0),
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)
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for pre_validator in pre.validators:
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post_validator = Validator(
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pubkey=pre_validator.pubkey,
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withdrawal_credentials=pre_validator.withdrawal_credentials,
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effective_balance=pre_validator.effective_balance,
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slashed=pre_validator.slashed,
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activation_eligibility_epoch=pre_validator.activation_eligibility_epoch,
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activation_epoch=pre_validator.activation_epoch,
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exit_epoch=pre_validator.exit_epoch,
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withdrawable_epoch=pre_validator.withdrawable_epoch,
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fully_withdrawn_epoch=FAR_FUTURE_EPOCH,
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)
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post.validators.append(post_validator)
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return post
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```
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