Query the Counter Account

Each time the client runs, it increments the counter value stored in the counter account owned by the on-chain program.

Reading the Counter Value

1. The counter account is loaded by its derived pubkey
2. The data field of the account is deserialized into a Counter struct using Borsh
3. The count field is printed

#![allow(unused)]
fn main() {
let account = client.get_account(&counter_address)?;
let counter = Counter::try_from_slice(&account.data)?;
println!("Counter value {}", counter.count);
}

Every execution of cargo run increments the counter by 1.

Experiment: Concurrent Increments

If you start the validator in a clean state and run:

for _ in {0..99}; do cargo run; done

from two terminals simultaneously — the counter value should be 200. But it won’t be!

Why? Check all the entries in ~/.config/solana/cli/config.yml for the answer.

Using solana deploy Instead

If you deploy with solana deploy program.so instead of solana program deploy:

• The program is owned by the BPF loader (not upgradeable)
• A randomly generated program ID is assigned
• Pass it to the client via the program_id environment variable:

program_id=<generated_id> cargo run