Crate pallet_block_production_log

A Substrate pallet maintaining a consumable log of block production information.

Purpose of this pallet

This pallet keeps a log containing block producer IDs along with slot numbers of blocks produced by them. This log is updated every block and is meant to consumed by other features. The intended use of this pallet within the Partner Chains SDK is to expose block production data for consumption by the Block Participation feature implemented by the sp_block_participation and pallet_block_participation crates.

Usage - PC Builder

This pallet requires inherent data provided by the inherent data provider defined by sp_block_production_log crate. Consult the crate’s documentation for instruction on how to wire it into the node correctly.

Adding to the runtime

The pallet requires a minimal configuration. Consult the documentation for pallet::Config for details.

An example configuration for a runtime using Aura consensus might look like this:

impl pallet_block_production_log::Config for Runtime {
    type BlockProducerId = BlockAuthor;
    type WeightInfo = pallet_block_production_log::weights::SubstrateWeight<Runtime>;

    fn current_slot() -> sp_consensus_slots::Slot {
        let slot: u64 = pallet_aura::CurrentSlot::<Runtime>::get().into();
        sp_consensus_slots::Slot::from(slot)
    }

    #[cfg(feature = "runtime-benchmarks")]
    type BenchmarkHelper = PalletBlockProductionLogBenchmarkHelper;
}

Defining block producer ID

The pallet expects the Partner Chain to provide a type representing its block producers. This type can be as simple as an Aura public key but can also be a more complex type if block producers are not a homogenous group. For example, in the context of a Partner Chain using Ariadne committee selection, it’s typical to have two kinds of block producers: permissioned producers provided by the governance authority and registered candidates recruited from among Cardano stake pool operators. In this instance an example author type could be:

use sidechain_domain::*;

pub enum BlockAuthor {
    Incentivized(CrossChainPublicKey, StakePoolPublicKey),
    ProBono(CrossChainPublicKey),
}

Keep in mind that other Partner Chains SDK components put their own constraints on the block author type that need to be adhered to for a Partner Chain to integrated them.

Support for adding to a running chain

The pallet and its inherent data provider defined in sp_block_production_log are written in a way that allows for adding it to an already live chain. The pallet allows for an initial period where inherent data is unavailable and considers its inherent extrinsic required only after the first block where inherent data is provided. Conversely, the inherent data provider is active only when the pallet and its runtime API is present for it to call.

Consuming the log

Important: Consuming the log is a destructive operation. Multiple features should not consume the log data unless they are coordinated to read and clear the same log prefix.

The pallet exposes three functions that allow other pallets to consume its data: take_prefix, peek_prefix and drop_prefix. Any feature using the log should be able to identify the slot number up to which it should process the log data and either:

• call take_prefix from some pallet’s logic and process the returned data within the same block
• call peek_prefix inside an inherent data provider and use drop_prefix from the corresponding pallet to clear the previously peeked data within the same block

It is critically important to drop exactly the prefix processed to avoid either skipping or double-counting some blocks.

Usage - PC user

This pallet does not expose any user-facing functionalities.

Re-exports

pub use weights::WeightInfo;

pub use pallet::*;

Modules

pallet

The pallet module in each FRAME pallet hosts the most important items needed to construct this pallet.

weights

Autogenerated weights for pallet_block_production_log