# Requesters and Sponsors

Table of Contents

As a developer it helps to understand what a requester is and what a sponsor does. They are both important parts of the Airnode ecosystem. This doc will further define them and walk you through the process to derive a sponsor wallet and to sponsor a requester using the admin CLI commands.

# What is a Requester?

The term requester is important to remember. When requester is mentioned, the reference is to your smart contract that calls an Airnode.

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As an example see the myContract.sol contract in the diagram within the Overview doc, it is a requester.

# What is a Sponsor?

Equally important is the term sponsor. A sponsor is an entity such as yourself, an organization, etc. Sponsors create relationships between requesters and Airnodes.

As a sponsor you will use the address of an Ethereum account (called a sponsorAddress) from a digital wallet you own to "sponsor a requester" and then with the same sponsorAddress "derive a sponsorWallet" for an Airnode. This action creates a relationship between a sponsor's requester and a particular Airnode. You do this because a sponsor is the entity that pays for the fulfillment of a request, the gas costs the Airnode will incur. These costs will be withdrawn from the sponsorWallet of the Airnode when the requester calls it.

In the diagram below a sponsor uses a mnemonic to sponsor a requester with the Admin CLI. The CLI will use the default address of the mnemonic as the sponsorAddress for the sponsorship. Next the sponsor will derive a sponsorWallet for an Airnode using the same sponsorAddress.

Because the requester was sponsored with the same sponsorAddress that was used to derive the sponsorWallet of the Airnode, the requester can now make requests of the Airnode.

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In the above diagram it is possible to use the same sponsorAddress (0xF4...dDyu9) to derive other sponsor wallets for other Airnodes. And it is possible to sponsor more than one requester with this same sponsorAddress. However it is important to remember that all requesters can now access all the Airnodes regardless if they need to. There is no harm in this scenario.

# Advanced Scenarios

  • Two requesters sponsored with the same sponsorAddress (0xF4...dDyu9) could access the same Airnode having a sponsor wallet derived by sponsorAddress (0xF4...dDyu9).

  • Using two separate sponsorAddresses (from two different Ethereum accounts), you can derive two separate sponsor wallets for the same Airnode, say (0xF4...dDyu9) and (0xG9...fFzc5). Then you can sponsor one requester each with (0xF4...dDyu9) and the other with (0xG9...fFzc5). Now each requester will deplete funds from a separate sponsor wallet.

  • You have derived two sponsor wallets for two different Airnodes using different sponsorAddresses, say (0xF4...dDyu9) and (0xG9...fFzc5). You have one requester that needs to makes requests from each Airnode. Simply sponsor the requester twice with both sponsorAddresses.

# Things to Remember

When you sponsor a requester with a sponsorAddress, you are giving it permission to use the sponsor wallet associated with the Airnode (created with the same sponsorAddress).

When the requester makes a request to the Airnode, the Airnode will use funds from the corresponding sponsor wallet to pay gas costs in response to the request. Therefore the sponsor pays for the fulfillment of the request.

# Admin CLI Commands

There are several sponsor and requester related commands in the Admin CLI Commands package. You can also see a list of available commands using npx @api3/airnode-admin --help.

In the next two sections of this doc you will use two commands from the @api3/airnode-admin package to sponsor a requester and to derive a sponsor wallet.

  1. sponsor-requester sponsors a requester.
  2. derive-sponsor-wallet-addresscreates a sponsor wallet associated with an Airnode.

# How to Sponsor a Requester

When a sponsor uses the same sponsorAddress to "sponsor a requester" and to "derive a sponsor wallet" for an Airnode, the requester will have permission to make requests to the Airnode on behave of the sponsor. This allows the sponsor to cover the gas costs incurred by the Airnode when responding to the request. Sponsors need to keep their sponsor wallets topped off if they want Airnodes to fulfill requests made by their requesters. However this does not cover the cost of API data that the Airnode serves, see API Provider Fees.

To sponsor a requester execute the sponsor-requester command using the parameters detailed in the list below. Your requester should already be deployed on-chain. This command has transaction gas costs.

  • providerURL A blockchain provider URL (such as Infura) with providerID for the desired network.
  • mnemonic Used for gas costs to fund the sponsorship and used to derive the sponsorAddress from the default address. The sponsorAddress will be needed to derive a sponsorWallet for an Airnode.
  • requesterAddress The address of the requester contract.

The command sponsor-requester will return the requesterAddress and sponsorAddress.

# How to Derive a Sponsor Wallet

To use a particular Airnode you must derive a sponsor wallet. Once the sponsor wallet is created it must be funded using the public address returned by the commandderive-sponsor-wallet-address. Each Airnode keeps a separate list of individual sponsor wallets that can access the Airnode. Learn more about sponsor wallets.

To derive a sponsor wallet for an Airnode execute the derive-sponsor-wallet-address command using the parameters detailed in the list below. There are no transaction gas costs to do so.

  • providerURL a blockchain provider URL (such as Infura) with providerID for a desired network
  • airnode of address the desired Airnode
  • sponsor the sponsorAddress (an address of an Ethereum account) owned by a sponsor

The command derive-sponsor-wallet-address will return the public address of the sponsor wallet to be funded by the sponsor.

If you forget the public address of the sponsor wallet simply run derive-sponsor-wallet-address again. Since the wallet already exists for the airnodeAddress/sponsorAddress pair it will just return the address.

Sponsors should not fund a sponsorWallet with more then they can trust the Airnode with, as the Airnode controls the private key to the sponsorWallet. The deployer of such Airnode undertakes no custody obligations, and the risk of loss or misuse of any excess funds sent to the sponsorWallet remains with the sponsor.

# Record Keeping

During and after deriving a sponsor wallets and sponsoring requesters there are a few things to keep track of.

Item Description
requesters Record which sponsorAddress (from the supplied mnemonic) was used to sponsor a requester.
sponsor wallets Record which sponsorAddress was used to create a sponsorWallet for an Airnode.
sponsor wallets Record the sponsorWalletAddress of the sponsorWallet derived for an Airnode. For each Airnode you have derived a sponsorWallet, the Airnode keeps the private key and returns the public address which is used to fund the sponsorWallet.

You can acquire the public address of a sponsorWallet later, if you loose it, by running the command derive-sponsor-wallet-address again. Since the sponsorWallet was already created for the sponsorAddress/airnodeAddress pair, the command will only return the public address for the wallet. However you must use the same sponsorAddress used when the wallet was first created or a new sponsorWallet will be created.

Last Updated: 10/26/2021, 11:28:49 AM