Fee Data Flow

The basic idea of incentivizing an external AWM Relayer to relay our message is to deposit an amount of an ERC-20 token into the Interchain Messaging contract as a reward for whichever relayer delivers our message.

Let's see how the fees are transferred from the user at the very beginning of sending a Cross Chain message, up to the point where the relayer is able to claim the fee.

We are using the following emoji guide to show the actors of each action:

👩 User

📜 Cross-Chain dApp

👾 TeleporterMessenger

🛸 Relayer

Previous to Sending the Message:

• 👩 The message sender (user) requires to approve the Cross-Avalanche L1 dApp as a spender on the ERC20 contract to be used as fee.

Sending the Message:

• 👩 User sends a message.
• 📜 Fee funds (previously approved) are transferred from the user's wallet to the Cross-Chain dApp.
• 📜 Cross-Chain dApp approves the Interchain Messaging Contract to spend the ERC20 fee tokens.
• 👾 Fee tokens are transferred into the Interchain Messaging Contract.
• 👾 Interchain Messaging assigns a unique ID to the Message and keeps track of the fee Info.
• 🛸 Relayer can now pick and deliver the Message.

Message Delivered in the Destination Chain:

• 👾 Interchain Messaging in the Destination Chain generates a receipt with the messageID and Relayer address who delivered the message.
• Receipt is sent back to the Source Chain.
• 🛸 Relayers can send the receipts back to the Source Chain themselves or wait until a new (unrelated) message is sent now from the once Destination Chain to the former Source chain. Messages include up to 5 pending receipts in a message.

Once Message is Received in the Source Chain:

• 👾 The Interchain Messaging marks the messageID as received and increases the Relayer redeemable reward.
• 🛸 The relayer can now claim its unlocked rewards.

As you can see, there are just a few actions you as a cross-chain dApp developer need to implement so dApp works smoothly with fees, everything else is being done by the Interchain Messaging contract and the Relayer.

If you run your own relayer, you don't have to attach any fees.