Setup Counter Account

Solana on-chain programs are stateless — they cannot persist data between invocations. State is stored in accounts that the program owns.

Note: Programs are also stored in accounts, marked as executable. Deploy with solana program deploy (upgradeable) vs solana deploy (final, uses BPFLoader).

Account Setup Flow

1. Retrieve Payer Pubkey

The payer pubkey is derived from ~/.config/solana/id.json. The program ID is derived from ./target/deploy/program-keypair.json. If the program has not been built, setup fails immediately.

2. Derive Counter Account Address

The counter account pubkey is derived from the payer pubkey, a seed string, and the program ID (owner of the account). A query is made to the chain:

• Account exists → early exit, nothing to set up
• Account does not exist → proceed to create it

3. Calculate Rent-Exempt Balance

Calculate the minimum balance required for the counter account to stay rent-exempt based on its data size. The Counter struct:

#![allow(unused)]
fn main() {
struct Counter {
    count: u64,      // 8 bytes
}
}

It derives BorshSerialize and BorshDeserialize for serialization. A helper computes the struct size:

#![allow(unused)]
fn main() {
const COUNTER_SIZE: usize = std::mem::size_of::<u64>();
}

The rent exemption amount is fetched from the network:

#![allow(unused)]
fn main() {
let lamports = client.get_minimum_balance_for_rent_exemption(COUNTER_SIZE)?;
}

4. Construct Create Account Instruction

The system instruction for creating the counter account is constructed with the lamports amount, space, and owner (program ID).

5. Query Blockhash

The latest blockhash is retrieved from the network. This measures how recent the client’s view of the network is and is used to accept/reject transactions.

6. Calculate Fee

The network is queried for the required fee for the transaction message — the cost of executing the transaction.

7. Airdrop Lamports

The total cost (rent exemption + transaction fee) is funded via an airdrop:

#![allow(unused)]
fn main() {
client.request_airdrop(&payer, total_lamports)?;
}

The airdrop can be skipped by setting the skip_airdrop environment variable to a non-empty value, or if the payer already has sufficient balance.

8. Send Transaction

The create-account transaction is sent to the network and a transaction signature is returned.