EIP 1559 on Ethereum VS side chains

[Madeindreams]

Greetings!

I am trying to figure out what is going on with the EIP 1559 on sidechains, in this case, Polygon and have yet to test other chains.

So as per my understanding.

EIP 1559 requires the base fees, the priority fees, and the max fees should be grater than the base + priority.

When I query the RPC on Ethereum, I get a value that reflect the state of the network (as per Etherscan).

Example;

Priority Fee: 2.5
Base Fee: 48.650542402
Max Fee: 99.801084804
Gas Price: 49.931691235

In this case the max fee allow me to spend base + priority. and these values are reflected on Etherscan.

Now on Polygon ;

Priority Fee: 2.5
Base Fee: 24.808958827
Max Fee: 52.117917654
Gas Price: 55.861286263

The priority is also set to 2.5, however Polygon scan return something way higher than this.

The priority fee on Polygon is actually the gas price minus the base fee. So in this case the max fee should be greater or equal to the gas price. But the max fees returned by the RPC are always lower than the base + priority.

So is this really an EIP 1559 implementation? Anyway I look at it I end up using the gas price instead of the actual EIP 1559 base on the state of the network.

[ricmoo]

Polygon did not implement EIP-1559 according to the specification, and made their own decisions, which I still do not understand.

The baseFee come from in-protocol calculations, based on previous block “fullness”. A block is only a candidate to be mined if maxFeePerGas > baseFeePerGas. The priority fee is a bribe to further incentivize a miner. There is no such thing as gasPrice after EIP-1559; it doesn’t exist. Any API that returns it, is approximating a value that will hopefully work when broadcasting a legacy transaction; this is also a very bad idea, legacy transactions will never cost less than the EIP-1559 equivalent, but will almost certainly cost more.

The point of maximumPriorityFeePerGas is to price in the cost of risk due to Uncle Risk and MEV Risk, which when launched was approximated to be 2.5 gwei, but was later able to be reduced to 1.5 gwei (the cost due to MEV Risk was lower than expected; like due to EIP-1559 itself. ;)).

If you update to a newer version of ether, 1.5 gwei will be used instead; which doesn’t help you.

I’m v6, there is a way for a network to specify an alternate priority fee, right now it is hard coded to 35 for Polygon, but if you have a better source for where Polygon providers should pull it from I’m all ears.

So for v5, you need to specify a custom maxPriorityFeePerGas in your transactions on Polygon and other networks that either have alternate risk costs or chose a different calculation.

Does that make sense?

[Madeindreams]

Yes it does make sense. Thank you @ricmoo! If the priority fees are hardcoded to 35, this probably means that when the priority reach 60 my transaction might take longer to get picked up. However in all my test case, legacy gasPrice is always equal to base+priority.
So I'm left thinking that Polygon still use the gas price deep within and kind of faked the EIP 1559 on the RPC to match the gas price.

[ricmoo]

Thanks. That’s good to know. If I can programmatically compute their priority fee, I’d prefer it. But it also seems scary that a faulty value from the node could result in a crazy (and unnecessary) fee.

[Madeindreams]

Will let you know if I come up with something!