Choosing an interchain gas paymaster contract
Which IGP contract should you use?
Last updated
Which IGP contract should you use?
Last updated
There may be many interchain gas paymaster (IGP) contracts on a given chain, this guide helps you understand which one you should use to pay for message delivery.
Each relayer must deploy one or more IGP contracts through which it can accept payment to deliver messages to a remote chain.
Not all Relayers will be able to deliver all messages. For example, some relayers may only deliver messages between a specific subset of chains, or some relayers may only deliver messages between specific sender and recipient contracts.
Be sure that you're using an IGP for a relayer that is capable of delivering all of the messages that your application might send.
In some cases, this may mean using different IGP contracts depending on the destination of the message.
Many relayers will deploy two types of IGP contracts. Read below to understand which one to use and how to use it.
If the message recipient uses the default Interchain security modules, your application can make use of the DefaultIsmInterchainGasPaymaster.
The default ISM is the security module used if no security model is specified explicitly by the recipient. Learn more about Specifying an ISM.
When using the DefaultIsmInterchainGasPaymaster, the _gasAmount to use when calling the payForGas or quoteGasPayment functions only needs to be the amount of gas that your message's recipient handle function will use at the destination.
Behind the scenes, the DefaultIsmInterchainGasPaymaster is configured to automatically add to the provided _gasAmount all overhead gas amounts that your message will use at its destination-- this includes any gas used by the Mailbox or the default ISM (for example, verifying validator signatures). This allows messages to be fully paid for without requiring any knowledge of the internal gas usage of the destination's Mailbox contract or default ISM when a message is processed.
Find the deployed contract addresses for the Abacus Works relayer.
If the message recipient is Specifying an ISM other than the default ISM, you should instead use the InterchainGasPaymaster.
This IGP requires that the _gasAmount used when calling the payForGas or quoteGasPayment functions accounts for all gas required by the relayer to process the message on the destination chain.
The gas amount required to process the message should include:
Intrinsic transaction gas costs, including gas for calldata
The amount of gas used by the Mailbox.process function
The amount of gas used by the ISM to verify the message
The amount of gas used by the message's recipient handle function
| Recipient specifies an ISM | IGP Contract | _gasAmount |
|---|---|---|
No |
| Only recipient |
Yes |
| All gas used by a transaction that processes the message |
Find the deployed contract addresses for the Abacus Works relayer.