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  • Branislav Kontur's avatar
    [pallet-xcm] Adjust benchmarks (teleport_assets/reserve_transfer_assets) not relying on ED (#3464) · 3d9439f6
    Branislav Kontur authored
    
    
    ## Problem
    During the bumping of the `polkadot-fellows` repository to
    `[email protected]`, I encountered a situation where the benchmarks
    `teleport_assets` and `reserve_transfer_assets` in AssetHubKusama
    started to fail. This issue arose due to a decreased ED balance for
    AssetHubs introduced
    [here](https://github.com/polkadot-fellows/runtimes/pull/158/files#diff-80668ff8e793b64f36a9a3ec512df5cbca4ad448c157a5d81abda1b15f35f1daR213),
    and also because of a [missing CI
    pipeline](https://github.com/polkadot-fellows/runtimes/issues/197) to
    check the benchmarks, which went unnoticed.
    
    These benchmarks expect the `caller` to have enough:
    1. balance to transfer (BTT)
    2. balance for paying delivery (BFPD).
     
    So the initial balance was calculated as `ED * 100`, which seems
    reasonable:
    ```
    const ED_MULTIPLIER: u32 = 100;
    let balance = existential_deposit.saturating_mul(ED_MULTIPLIER.into());`
    ```
    The problem arises when the price for delivery is 100 times higher than
    the existential deposit. In other words, when `ED * 100` does not cover
    `BTT` + `BFPD`.
    
    I check AHR/AHW/AHK/AHP and this problem has only AssetHubKusama
    ```
    ED: 3333333
    calculated price to parent delivery:  1031666634  (from xcm logs from the benchmark)
    ---
    
    3333333 * 100 - BTT(3333333) - BFPD(1031666634) = −701666667
    ```
    which results in the error;
    ```
    2024-02-23 09:19:42 Unable to charge fee with error Module(ModuleError { index: 31, error: [17, 0, 0, 0], message: Some("FeesNotMet") })
    Error: Input("Benchmark pallet_xcm::reserve_transfer_assets failed: FeesNotMet")
         
    ```
    
    ## Solution
    
    The benchmarks `teleport_assets` and `reserve_transfer_assets` were
    fixed by removing `ED * 100` and replacing it with `DeliveryHelper`
    logic, which calculates the (almost real) price for delivery and sets it
    along with the existential deposit as the initial balance for the
    account used in the benchmark.
    
    
    ## TODO
    
    - [ ] patch for 1.6 -
    https://github.com/paritytech/polkadot-sdk/pull/3466
    - [ ] patch for 1.7 -
    https://github.com/paritytech/polkadot-sdk/pull/3465
    - [ ] patch for 1.8 - TODO: PR
    
    ---------
    
    Co-authored-by: default avatarFrancisco Aguirre <[email protected]>
    3d9439f6