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Sysvar Cluster Data

Velas exposes a variety of cluster state data to programs via sysvar accounts. These accounts are populated at known addresses published along with the account layouts in the solana-program crate, and outlined below.

To include sysvar data in program operations, pass the sysvar account address in the list of accounts in a transaction. The account can be read in your instruction processor like any other account. Access to sysvars accounts is always readonly.

Clock​

The Clock sysvar contains data on cluster time, including the current slot, epoch, and estimated wall-clock Unix timestamp. It is updated every slot.

  • Address: SysvarC1ock11111111111111111111111111111111
  • Layout: Clock

Fields:

  • slot: the current slot
  • epoch_start_timestamp: the Unix timestamp of the first slot in this epoch. In the first slot of an epoch, this timestamp is identical to the unix_timestamp (below).
  • epoch: the current epoch
  • leader_schedule_epoch: the most recent epoch for which the leader schedule has already been generated
  • unix_timestamp: the Unix timestamp of this slot. Each slot has an estimated duration based on Proof of History. But in reality, slots may elapse faster and slower than this estimate. As a result, the Unix timestamp of a slot is generated based on oracle input from voting validators. This timestamp is calculated as the stake-weighted median of timestamp estimates provided by votes, bounded by the expected time elapsed since the start of the epoch.

More explicitly: for each slot, the most recent vote timestamp provided by each validator is used to generate a timestamp estimate for the current slot (the elapsed slots since the vote timestamp are assumed to be Bank::ns_per_slot). Each timestamp estimate is associated with the stake delegated to that vote account to create a distribution of timestamps by stake. The median timestamp is used as the unix_timestamp, unless the elapsed time since the epoch_start_timestamp has deviated from the expected elapsed time by more than 25%.

EpochSchedule​

The EpochSchedule sysvar contains epoch scheduling constants that are set in genesis, and enables calculating the number of slots in a given epoch, the epoch for a given slot, etc. (Note: the epoch schedule is distinct from the leader schedule)

  • Address: SysvarEpochSchedu1e111111111111111111111111
  • Layout: EpochSchedule

Fees​

The Fees sysvar contains the fee calculator for the current slot. It is updated every slot, based on the fee-rate governor.

  • Address: SysvarFees111111111111111111111111111111111
  • Layout: Fees

Instructions​

The Instructions sysvar contains the serialized instructions in a Message while that Message is being processed. This allows program instructions to reference other instructions in the same transaction.

  • Address: Sysvar1nstructions1111111111111111111111111
  • Layout: Instructions

RecentBlockhashes​

The RecentBlockhashes sysvar contains the active recent blockhashes as well as their associated fee calculators. It is updated every slot.

Rent​

The Rent sysvar contains the rental rate. Currently, the rate is static and set in genesis. The Rent burn percentage is modified by manual feature activation.

  • Address: SysvarRent111111111111111111111111111111111
  • Layout: Rent

SlotHashes​

The SlotHashes sysvar contains the most recent hashes of the slot's parent banks. It is updated every slot.

  • Address: SysvarS1otHashes111111111111111111111111111
  • Layout: SlotHashes

SlotHistory​

The SlotHistory sysvar contains a bitvector of slots present over the last epoch. It is updated every slot.

  • Address: SysvarS1otHistory11111111111111111111111111
  • Layout: SlotHistory

StakeHistory​

The StakeHistory sysvar contains the history of cluster-wide stake activations and de-activations per epoch. It is updated at the start of every epoch.

  • Address: SysvarStakeHistory1111111111111111111111111
  • Layout: StakeHistory