Meta Tx (Meta Transaction) Pallet

This pallet enables the dispatch of transactions that are authorized by one party (the signer) and executed by an untrusted third party (the relayer), who covers the transaction fees.

Pallet API

See the pallet module for more information about the interfaces this pallet exposes, including its configuration trait, dispatchables, storage items, events and errors.

Overview

The pallet provides a client-level API, typically not meant for direct use by end users. A meta transaction, constructed with the help of a wallet, contains a target call, necessary extensions, and the signer's signature. This transaction is then broadcast, and any interested relayer can pick it up and execute it. The relayer submits a regular transaction via the dispatch function, passing the meta transaction as an argument to execute the target call on behalf of the signer while covering the fees.

Example

Low-Level / Implementation Details

The structure of a meta transaction is identical to the General transaction. It contains the target call along with a configurable set of extensions and its associated version. Typically, these extensions include type like pallet_verify_signature::VerifySignature, which provides the signer address and the signature of the payload, encompassing the call and the meta-transaction’s configurations, such as its mortality. The extensions follow the same TransactionExtension contract, and common types such as frame_system::CheckGenesis, frame_system::CheckMortality, frame_system::CheckNonce, etc., are applicable in the context of meta transactions. Check the mock setup for the example.