Setting Base Gas Fees of Your Precompile

Gas is used for spam prevention. If our precompile is accessible to everyone on our Subnet, it is important to set the gas cost in a way that lets users economically utilize it in their apps, yet prevents spammers from spamming our blockchain with calls to the precompile.

In this section, we'll modify the default values of the gas costs of our Calculator precompile. By default, all user-defined functions have a gas cost of 1. While this is good news for the average user, allowing users to call computationally expensive functions can leave our blockchain vulnerable to Denial-of-Service (DoS) attacks.

We can find the default gas cost values for our functions in calculator/contract.go. Following the import statements, you should see:

const (
    // Gas costs for each function. These are set to 1 by default.
    // You should set a gas cost for each function in your contract.
    // Generally, you should not set gas costs very low as this may cause your network to be vulnerable to DoS attacks.
    // There are some predefined gas costs in contract/utils.go that you can use.
    AddGasCost     uint64 = 1 /* SET A GAS COST HERE */
    NextTwoGasCost uint64 = 1 /* SET A GAS COST HERE */
    RepeatGasCost  uint64 = 1 /* SET A GAS COST HERE */
)

The variables AddGasCost, NextTwoGasCost, and RepeatGasCost are the gas costs of the add, nextTwo, and repeat functions, respectively. As you can see, they are currently set to 1.

However, changing the gas cost is as easy as changing the values themselves. As an example, change the gas costs to 7.