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README.md

Day 12: Solana Sysvars Explained

Day 12 of RareSkills Solana Course.

Setup

  1. Configure Solana to run on localhost: solana config set --url localhost
  2. Run the test validator node on another terminal: solana-test-validator
  3. Run Solana logs on another terminal: solana logs
  4. Build Anchor program: anchor build
  5. Sync program_id with Anchor key: anchor keys sync
  6. Run tests: anchor test --skip-local-validator

Note

Solana sysvars

  • sysvars are read-only system accounts that give Solana programs access to the blockchain state, as well as network information.
  • in Anchor programs, sysvars can be accessed in two ways:
    • using Anchor's get method wrapper.
    • treating it as an account in the #[Derive(Accounts)] using its public address.
  • Here are a list of sysvars:
    • Clock: Used for time-related operations like getting the current time or slot number.
    • EpochSchedule: Contains information about epoch scheduling, including the epoch for a particular slot.
    • Rent: Contains the rental rate and information like the minimum balance requirements to keep an account rent exempt.
    • Fees: Contains the fee calculator for the current slot. The fee calculator provides information on how many lamports are paid per signature in a Solana transaction.
    • EpochRewards: The EpochRewards sysvar holds a record of epoch rewards distribution in Solana, including block rewards and staking rewards.
    • RecentBlockhashes: Contains the active recent block hashes.
    • SlotHashes: Contains history of recent slot hashes.
    • SlotHistory: Holds an array of slots available during the most recent epoch in Solana, and it is updated every time a new slot is processed.
    • StakeHistory: maintains a record of stake activations and deactivations for the entire network on a per-epoch basis, which is updated at the beginning of each epoch.
    • Instructions: To get access to the serialized instructions that are part of the current transaction.
    • LastRestartSlot: Contains the slot number of the last restart (the last time Solana restarted ) or zero if none ever happened. If the Solana blockchain were to crash and restart, an application can use this information to determine if it should wait until things stabilize.

Solana slots and blocks

  • A slot is a window of time (around 400 ms) where a designated leader can produce a block.
  • A slot might not contain a block if the block leader failed to produce a block during that slot.

References