Sponsored Transactions for Polkadot SDK

Small proof-of-concept for sponsored transactions in Polkadot SDK. Similar to how the sudo key is set in a Substrate chain, you can set a payer key using the Spontra pallet. You can then sponsor specific transactions using the sponsor_call extrinsic. Once a call is marked as sponsored, the payer pays for that call.

Note: This solution is not analyzed for security best practices. Don't use it in production without a thorough audit.

Setup and Run

Build

Use the following command to build the node without launching it:

cargo build --release

Local Development Chain

The following command starts a single-node development chain that doesn't persist state:

./target/release/spontra-node --dev

To purge the development chain's state, run the following command:

./target/release/spontra-node purge-chain --dev

To start the development chain with detailed logging, run the following command:

RUST_BACKTRACE=1 ./target/release/spontra-node -ldebug --dev

Development chains:

• Maintain state in a tmp folder while the node is running.
• Use the Alice and Bob accounts as default validator authorities.
• Use the Alice account as the default sudo account.
• Are preconfigured with a genesis state (/node/src/chain_spec.rs) that includes several pre-funded development accounts.

To persist chain state between runs, specify a base path by running a command similar to the following:

// Create a folder to use as the db base path
$ mkdir my-chain-state

// Use of that folder to store the chain state
$ ./target/release/spontra-node --dev --base-path ./my-chain-state/

// Check the folder structure created inside the base path after running the chain
$ ls ./my-chain-state
chains
$ ls ./my-chain-state/chains/
dev
$ ls ./my-chain-state/chains/dev
db keystore network

Test Data

The Sponsor Call extrinsic takes pallet name and call name as hex. Use the following test data:

Template: 0x54656d706c617465

do_something: 0x646f5f736f6d657468696e67

Balances: 0x42616c616e636573

transfer_keep_alive: 0x7472616e736665725f6b6565705f616c697665

License

The code within this repository is licensed under Apache-2.0 license. See the LICENSE file for more details.