Logging in benchmarking mode

Question

I am implementing benchmark to calculate weight in my pallet and need to print some data I was trying to use if_std println! but got nothing. What the best way to make printouts for debugging benchmarks.rs?

benchmarks! {
    create_xyz {
        let index = <NextXYZIndex<T>>::get();
        println!("index:{}", index);
        let caller: T::AccountId = whitelisted_caller();
    }: _(RawOrigin::Signed(caller), index)
}

Answer 1

You can use the info! macro or similar from frame_support::log as such:

use frame_support::log::info;

benchmarks! {
    something {

        info!("Logging works!");

    }: _(args...)
}

This is only helpful for debugging though.

Answer 2

I would probably not put logs in your production benchmarks, but if you are trying to debug things, you can add a println! statement and then run the benchmark tests:

cargo test -p pallet-name --features runtime-benchmarks

This will work as long as you have included the:

impl_benchmark_test_suite!(Pallet, crate::tests::new_test_ext(), crate::tests::Test);