Action

Actions are the fundamental unit of interaction. They are the building block of a state machine that captures the user's input. These are analogous to transactions in a regular blockchain system with the difference that these are just signed messages that the users send to the micro-rollup.

Actions are used to trigger a state mutation in the MRU which is handled by the state transition function.

Actions vs transactions

Actions are similar to transactions in a blockchain system. The key difference is that actions are not broadcasted to any network. They are just signed messages that the users send to the micro-rollup.

Action Cost

Stackr does not enforce a cost for an action in this version. However, Micro-Rollup developers are free to design their actions to include a cost component to charge users.

Action Format

In a gist, an action has the following properties to be able to mutate a state machine:

export interface IAction {
  identifier: string;
  msgSender: AddressLike;
  signature: SignatureLike;
  payload: AllowedInputTypes;
}

• identifier: A unique identifier for the action. This allows the state machine to redirect it to the correct state transition function.
• msgSender: The address of the user who sent the action.
• signature: The signature of the action. This is used to authenticate the user who signed the action.
• payload: The data of the action. This is the actual data that the action is supposed to mutate the state with.

Action Creation

Actions are constructed via ActionSchemas. More on this here.

Once you've generated the schema for your action, you can use the actionFrom function on your schema to create a new action. The schema ensures that your action is well-formed and adheres to the schema's rules while also being EIP 712 'signable'. Here's an example of how you can create an action from a schema:

const action = NewSchema.actionFrom({
  inputs,
  signature,
  msgSender: wallet.address,
});

• The inputs are of whatever type you defined in your schema.
• The signature is an EIP712 signature over the action's inputs. This is used to authenticate the user who signed the action. It can be created using your action schema like this:

const signature = await wallet.signTypedData(
  schema.domain,
  schema.EIP712TypedData.types,
  payload
);

• The msgSender is the address of the user who sent the action.

Your action is now ready for submission!

Action Submission

Your action can now be submitted to the Micro-Rollup's State Machine. All this requires calling the submitAction function on your Micro-Rollup.

let ack = await rollup.submitAction("<REDUCER-NAME>", action);

We also pass in the name of the reducer that will be handling your action. These are state transition functions that you will be defining in the src/stackr/transitions.ts file. On succesful submission, you will recieve an Acknowledment object that acts like a transaction receipt and is also considered a C0 confirmation. This is proof of the action being successfully submitted to the state machine.

EIP-712 Signing

EIP 712 is a standard for signing structured data. It is used to sign actions in this version of Stackr. This also makes Stackr Actions compatible with existing browser wallet extensions and other EVM-friendly wallet implementations.

Action Execution

Once the action is submitted, it goes in the rollup's action pool, similar to a traditional mempool. The action stays in the pool until picked up by a sequencer.

The sequencer picks up the action, creates a block and sends that block to the executor. The executor then executes the block and updates the state of the rollup.