How to reduce eth_chainId calls?

[s1na]

I'm doing a sequence of rpc calls (getBlock) using the JsonRpcProvider and for every request I'm observing a chainId request which effectively doubles the RTTs. I was wondering why that is necessary and can't be only done once during provider instantiation?

edit: my ethers version is at v5.5.4

[ricmoo]

If you are connecting to a JSON-RPC node that cannot change its chain ID, you probably want to use the StaticJsonRpcProvider, which doesn't perform this check.

It is in general necessary because many JSON-RPC connections, such as MetaMask, allow the user to change the chain ID on a whim, by clicking a drop-down in the UI.

This will cause complete chaos if the check for chain ID is not made. For example, if you call getTransactionNonce on Ropsten and then send a transaction on mainnet, the nonce will likely not match, resulting in ether a NONCE_EXPIRED error or a transaction that will never get mined. Likewise, if you are querying for events, and the block number drastically changes, you are then possibly querying historic events or distant future events, when you intended to query for current events.

But this is why the StaticJsonRpcProvider exists. :)

[s1na]

Ah makes sense thanks for the explanation. I wanted to ask for a StaticJsonRpcBatchProvider but one eth_chainId for a batch of requests isn't that bad :)

[PawlowskiAdrian]

reading the code, adding middleware for caching solves this problem. This RPC method was added to caching middleware (web3/middleware/cache.py) -> ethereum/web3.py@3e8f07c

import web3
from web3.middleware import simple_cache_middleware

web3.middleware_onion.inject(simple_cache_middleware, layer=0)

[micwallace]

@ricmoo I noticed this provider no longer exists in v6? Can you confirm that this is the new equivalent?

const provider = new JsonRpcProvider("...", "mainnet", {
	staticNetwork: Network.from("mainnet")
});

[ricmoo]

It exists in v6. That snippet is from v6. :)

[micwallace]

@ricmoo But in v5 there was StaticJsonRpcProvider. This class doesn't exist in v6.
Looks like from the code comments this is the replacement and it works well.