where does provider.getGasPrice() get gas price from? can we trust it to work in production accurately

[metayash]

lately we've seen polygon gas price sky rocket. this has caused some problems for me in writing automated backends where my transaction keep getting stuck. so whenever I've used provider.getGasPrice() and then increase this by 1.5x the transaction gets mined pretty quickly for me ofcourse.

• can getGasPrice() method be safely used in production backends i.e will it always return a correct/or close to correct value? My worry here is if it returns an incorrect crazy high gas price, it could cause to drain all the funds in the account. thanks ✌️

[ricmoo]

I don’t know much about Polygon, but it sounds like they are not using Gas Fee Markets (EIP-1559), so the getGasPrice can only be as accurate as it is, and there is no good way for it to be safe or prevent swinging wildly.

Before EIP-1559, Ethereum had third-party services (like https://ethgasstation.info), which could better approximate a safe value to use, so maybe there is something similar for Polygon. You can also run your own gas price oracle.

I expect their gas prices will continue to climb though, as the only reason Polygon was ever cheap was because it was less popular, so as it becomes more and more popular, demand for its capacity will increase, which means gas prices must increase to compensate.

[htadashi]

@ricmoo Polygon adopted EIP-1559 on January 18th :)

But it seems that they didn't implement the .baseFee property on the Block object, as running

(await polygonProvider.getBlock("latest")).baseFee

returns undefined.

On the other hand, there is a maxFeePerGas on the FeeData object:

> await polygonProvider.getFeeData();
{
  maxFeePerGas: BigNumber { _hex: '0x9502f914', _isBigNumber: true },
  maxPriorityFeePerGas: BigNumber { _hex: '0x9502f900', _isBigNumber: true },
  gasPrice: BigNumber { _hex: '0x06fc23ac17', _isBigNumber: true }
}

Could this possibly cause some bug when using ethers.js?

[htadashi]

@metayash
One thing that may be the cause of this: Polygon adopted 1559, but the minimum gas price (validator fee) stills seems to be 30 gwei.
So even if the current base fee is pretty small, the minimum required for maxPriorityFee + baseFee should be greater than 30 gwei.
This chart may help you creating an algorithm for avoiding the tx getting stuck.