ValidatorsExitBusOracle

info

It's advised to read What is Lido Oracle mechanism before

What is ValidatorsExitBusOracle

A contract that implements an on-chain "source of truth" message bus between the protocol's off-chain oracle and off-chain observers, with the main goal of delivering validator exit requests to the Lido-participating node operators.

A report calculation consists of 4 key steps:

Calculate withdrawals amount to cover with ether.
Calculate ether rewards prediction per epoch.
Calculate withdrawal epoch for next validator eligible for exit to cover withdrawal requests if needed
Prepare validators exit order queue
Go through the queue until the exited validators’ balances cover all withdrawal requests (considering the predicated final exited balance of each validator).

note

Placed exit requests via ValidatorsExitBusOracle should be processed timely according to the ratified Lido on Ethereum Validator Exits Policy V1.0.

Access to lever methods is restricted using the functionality of the AccessControlEnumerable contract and a bunch of granular roles.

Report cycle

The oracle work is delineated by equal time periods called frames. In normal operation, oracles finalize a report in each frame (the frame duration is 75 Ethereum Consensus Layer epochs, each frame starts at ~04:00, ~12:00, ~20:00 UTC). Each frame has a reference slot and processing deadline. Report data is gathered by looking at the world state (both Ethereum Execution and Consensus Layers) at the moment of the frame's reference slot (including any state changes made in that slot), and must be processed before the frame's processing deadline.

Reference slot for each frame is set to the last slot of the epoch preceding the frame's first epoch. The processing deadline is set to the last slot of the last epoch of the frame.

It's worth noting that frame length can be changed. And if oracle report is delayed it does not extend the report period, unless it's missed. In this case, the next report will have the report period increased.

The frame includes these stages:

Waiting - oracle starts as a daemon and wakes up every 12 seconds (by default) in order to find the last finalized slot, trying to collate it with the expected reference slot;
Data collection: oracles monitor the state of both the execution and consensus layers and collect the data for the successfully arrived finalized reference slot;
Hash consensus: oracles analyze the report data, compile the report and submit its hash to the HashConsensus smart contract;
Core update report: once the quorum of hashes is reached, meaning more than half of the oracles submitted the same hash (i.e., 5 of 9 oracle committee members at the moment of writing), one of the oracles chosen in turn submits the actual report to the ValidatorsExitBusOracle contract, which triggers a chain of the ValidatorExitRequest events containing details about the next validators to be ejected (to initiate a voluntary exit from the Ethereum Consensus Layer side).

Report data

The function submitReportData() accepts the following ReportData structure.

struct ReportData {
    uint256 consensusVersion;
    uint256 refSlot;
    uint256 requestsCount;
    uint256 dataFormat;
    bytes data;
}

Oracle consensus info

consensusVersion — Version of the oracle consensus rules. A current version expected by the oracle can be obtained by calling getConsensusVersion().
refSlot — Reference slot for which the report was calculated. The state being reported must include all state changes resulting from the all blocks up to this reference slot (inclusive). The epoch containing the slot must be finalized prior to calculating the report.

Requests data

requestsCount — Total number of validator exit requests in this report. Must not be greater than the limit enforced by OracleReportSanityChecker.checkExitBusOracleReport.
dataFormat — Format of the validator exit requests data. Currently, only the DATA_FORMAT_LIST=1 value is supported.
data — Validator exit requests data. Can differ based on the data format, see the constant defining a specific data format here for more info.

Constants

DATA_FORMAT_LIST()

The list format of the validator exit requests data.

note

Each validator exit request is described by the following 64-byte array:

    MSB <------------------------------------------------------- LSB
    |  3 bytes   |  5 bytes   |     8 bytes      |    48 bytes     |
    |  moduleId  |  nodeOpId  |  validatorIndex  | validatorPubkey |

All requests are tightly packed into a byte array where requests follow one another without any separator or padding, and passed to the data field of the report structure.

Requests must be sorted in the ascending order by the following compound key: (moduleId, nodeOpId, validatorIndex).

uint256 public constant DATA_FORMAT_LIST = 1

SECONDS_PER_SLOT()

See https://ethereum.org/en/developers/docs/blocks/#block-time

note

always returns 12 seconds due to the Merge

uint256 public immutable SECONDS_PER_SLOT

GENESIS_TIME()

See https://blog.ethereum.org/2020/11/27/eth2-quick-update-no-21

note

always returns 1606824023 (December 1, 2020, 12:00:23pm UTC) on Mainnet

uint256 public immutable GENESIS_TIME

PAUSE_INFINITELY()

Special value for the infinite pause. See pauseFor and pauseUntil.

uint256 public constant PAUSE_INFINITELY = type(uint256).max

ProcessingState

struct ProcessingState {
    uint256 currentFrameRefSlot;
    uint256 processingDeadlineTime;
    bytes32 dataHash;
    bool dataSubmitted;
    uint256 dataFormat;
    uint256 requestsCount;
    uint256 requestsSubmitted;
}

currentFrameRefSlot — Reference slot for the current reporting frame.
processingDeadlineTime — The last time at which a report data can be submitted for the current reporting frame.
dataHash — Hash of the report data. Zero bytes if consensus on the hash hasn't been reached yet for the current reporting frame.
dataSubmitted — Whether any report data for the current reporting frame has been already submitted.
dataFormat — Format of the report data for the current reporting frame.
requestsCount — Total number of validator exit requests for the current reporting frame.
requestsSubmitted — How many validator exit requests are already submitted for the current reporting frame.

View methods

getTotalRequestsProcessed()

Returns the total number of validator exit requests ever processed across all received reports.

function getTotalRequestsProcessed() external view returns (uint256)

getLastRequestedValidatorIndices()

Returns the latest validator indices that were requested to exit for the given nodeOpIds in the given moduleId. For node operators that were never requested to exit any validator, index is set to -1.

function getLastRequestedValidatorIndices(uint256 moduleId, uint256[] calldata nodeOpIds)
        external view returns (int256[] memory)

Parameters

Name	Type	Description
`moduleId`	`uint256`	ID of the staking module.
`nodeOpIds`	`uint256`	IDs of the staking module's node operators.

Reverts

Reverts with ArgumentOutOfBounds() if moduleId > UINT24_MAX
Reverts with ArgumentOutOfBounds() if nodeOpId > UINT40_MAX

getProcessingState()

Returns data processing state for the current reporting frame. See the docs for the ProcessingState struct.

function getProcessingState() external view returns (ProcessingState memory result)

getConsensusContract()

Returns the address of the HashConsensus contract instance used by ValidatorsExitBusOracle.

function getConsensusContract() external view returns (address)

getConsensusReport()

Returns the last consensus report hash and metadata.

function getConsensusReport() external view returns (
    bytes32 hash,
    uint256 refSlot,
    uint256 processingDeadlineTime,
    bool processingStarted
)

getConsensusVersion()

Returns the current consensus version expected by the oracle contract.

note

Consensus version must change every time consensus rules change, meaning that an oracle looking at the same reference slot would calculate a different hash.

function getConsensusVersion() external view returns (uint256)

getContractVersion()

Returns the current contract version.

function getContractVersion() public view returns (uint256)

getLastProcessingRefSlot()

Returns the last reference slot for which processing of the report was started.

function getLastProcessingRefSlot() external view returns (uint256)

Returns

Name	Type	Description
`hash`	`bytes32`	The last reported hash
`refSlot`	`uint256`	The frame's reference slot: if the data the consensus is being reached upon includes or depends on any onchain state, this state should be queried at the reference slot. If the slot contains a block, the state should include all changes from that block.
`processingDeadlineTime`	`uint256`	Timestamp of the last slot at which a report can be reported and processed
`processingStarted`	`bool`	Has the processing of the report been started or not

getResumeSinceTimestamp()

Returns one of the timestamp values:

PAUSE_INFINITELY if paused permanently (i.e., with no expiration timestamp)
a first second when get contract get resumed if paused for specific duration (if timestamp ≥ block.timestamp)
some timestamp in past if not paused (if timestamp < block.timestamp)

function getResumeSinceTimestamp() external view returns (uint256 timestamp)

isPaused()

Returns whether the contract is paused or not at the moment.

function isPaused() public view returns (bool)

Methods

submitReportData()

Submits report data for processing.

function submitReportData(ReportData calldata data, uint256 contractVersion)
        external whenResumed

Parameters

Name	Type	Description
`data`	`ReportData`	The report data. See `ReportData` for details.
`contractVersion`	`uint256`	Expected version of the oracle contract.

Reverts

Reverts with SenderNotAllowed() if the caller doesn't have a SUBMIT_DATA_ROLE role and is not a member of the oracle committee.
Reverts with UnexpectedContractVersion(expectedVersion, version) if the provided contract version differs from the current one.
Reverts with UnexpectedConsensusVersion(expectedConsensusVersion, consensusVersion) if the provided consensus version differs from the expected one.
Reverts with UnexpectedRefSlot(report.refSlot, refSlot) if the provided reference slot differs from the current consensus frame's one.
Reverts with UnexpectedDataHash(report.hash, hash) if a keccak256 hash of the ABI-encoded data differs from the last hash.
Reverts with NoConsensusReportToProcess() if the report hash data is 0.
Reverts with RefSlotAlreadyProcessing() if the report reference slot is equal to the previous processing reference slot.
Reverts with InvalidRequestsData() if moduleId in the provided data is 0
Reverts with InvalidRequestsDataLength() if the provided data is packed incorrectly
Reverts with UnexpectedRequestsDataLength() if the length of the provided packed data is not equal data.requestsCount
Reverts with InvalidRequestsDataSortOrder when the provided data is not sorted
Reverts with NodeOpValidatorIndexMustIncrease( uint256 moduleId, uint256 nodeOpId, uint256 prevRequestedValidatorIndex, uint256 requestedValidatorIndex ) if requested validator index <= last requested index from the same module

pauseFor()

Pause accepting the reports data and forming new validator exit requests for the provided duration in seconds.

function pauseFor(uint256 _duration) external

Parameters

Name	Type	Description
`_duration`	`uint256`	pause duration, seconds (use `PAUSE_INFINITELY` for unlimited)

Reverts

Reverts with ResumedExpected() if contract is already paused
Reverts with AccessControl:... reason if sender has no PAUSE_ROLE
Reverts with ZeroPauseDuration() if zero duration is passed

pauseUntil()

Pause accepting the reports data and forming new validator exit requests till the given timestamp (inclusive).

function pauseUntil(uint256 _pauseUntilInclusive) external

Parameters

Name	Type	Description
`_pauseUntilInclusive`	`uint256`	the last second to pause until (inclusive)

Reverts

Reverts with ResumeSinceInPast() if the provided timestamp is in the past
Reverts with AccessControl:... reason if the sender has no PAUSE_ROLE
Reverts with ResumedExpected() if the contract is already paused

resume()

Resume accepting the reports data and forming new validator exit requests.

function resume() external

Reverts

Reverts with PausedExpected() if contract is already resumed (i.e., not paused)
Reverts with AccessControl:... reason if the sender has no RESUME_ROLE

Permissions

SUBMIT_DATA_ROLE()

An ACL role granting the permission to submit the data for a committee report.

bytes32 public constant SUBMIT_DATA_ROLE = keccak256("SUBMIT_DATA_ROLE")

PAUSE_ROLE()

An ACL role granting the permission to pause accepting the reports data and forming new validator exit requests.

bytes32 public constant PAUSE_ROLE = keccak256("PAUSE_ROLE")

RESUME_ROLE()

An ACL role granting the permission to resume accepting the reports data and forming new validator exit requests.

bytes32 public constant RESUME_ROLE = keccak256("RESUME_ROLE")

MANAGE_CONSENSUS_CONTRACT_ROLE()

An ACL role granting the permission to set the consensus contract address by calling setConsensusContract.

bytes32 public constant MANAGE_CONSENSUS_CONTRACT_ROLE = keccak256("MANAGE_CONSENSUS_CONTRACT_ROLE");

MANAGE_CONSENSUS_VERSION_ROLE()

An ACL role granting the permission to set the consensus version by calling setConsensusVersion.

bytes32 public constant MANAGE_CONSENSUS_VERSION_ROLE = keccak256("MANAGE_CONSENSUS_VERSION_ROLE");

Events

ValidatorExitRequest()

Emits when the new report data submitted for processing.

event ValidatorExitRequest(
    uint256 indexed stakingModuleId,
    uint256 indexed nodeOperatorId,
    uint256 indexed validatorIndex,
    bytes validatorPubkey,
    uint256 timestamp
)

WarnDataIncompleteProcessing()

Emits on attempt of new data submission having not all of the items processed yet.

event WarnDataIncompleteProcessing(
    uint256 indexed refSlot,
    uint256 requestsProcessed,
    uint256 requestsCount
)

Paused()

Emits when the contract is paused either by the pauseFor or pauseUntil calls.

event Paused(uint256 duration)

Resumed()

Emits when the contract is resumed by the resume call.

event Resumed()

What is ValidatorsExitBusOracle​

Report cycle​

Report data​

Constants​

DATA_FORMAT_LIST()​

SECONDS_PER_SLOT()​

GENESIS_TIME()​

PAUSE_INFINITELY()​

ProcessingState​

View methods​

getTotalRequestsProcessed()​

getLastRequestedValidatorIndices()​

Parameters​

Reverts​

getProcessingState()​

getConsensusContract()​

getConsensusReport()​

getConsensusVersion()​

getContractVersion()​

getLastProcessingRefSlot()​

Returns​

getResumeSinceTimestamp()​

isPaused()​

Methods​

submitReportData()​

Parameters​

Reverts​

pauseFor()​

Parameters​

Reverts​

pauseUntil()​

Parameters​

Reverts​

resume()​

Reverts​

Permissions​

SUBMIT_DATA_ROLE()​

PAUSE_ROLE()​

RESUME_ROLE()​

MANAGE_CONSENSUS_CONTRACT_ROLE()​

MANAGE_CONSENSUS_VERSION_ROLE()​

Events​

ValidatorExitRequest()​

WarnDataIncompleteProcessing()​

Paused()​

Resumed()​

What is ValidatorsExitBusOracle

Report cycle

Report data

Constants

DATA_FORMAT_LIST()

SECONDS_PER_SLOT()

GENESIS_TIME()

PAUSE_INFINITELY()

ProcessingState

View methods

getTotalRequestsProcessed()

getLastRequestedValidatorIndices()

Parameters

Reverts

getProcessingState()

getConsensusContract()

getConsensusReport()

getConsensusVersion()

getContractVersion()

getLastProcessingRefSlot()

Returns

getResumeSinceTimestamp()

isPaused()

Methods

submitReportData()

Parameters

Reverts

pauseFor()

Parameters

Reverts

pauseUntil()

Parameters

Reverts

resume()

Reverts

Permissions

SUBMIT_DATA_ROLE()

PAUSE_ROLE()

RESUME_ROLE()

MANAGE_CONSENSUS_CONTRACT_ROLE()

MANAGE_CONSENSUS_VERSION_ROLE()

Events

ValidatorExitRequest()

WarnDataIncompleteProcessing()

Paused()

Resumed()