Contract events not being emitted reliably

[firatkaratas]

Ethers Version

5.6.7

Search Terms

alchemy, event, eventfilter, optimism

Describe the Problem

Hey all,

I'm having a problem with contract events being not reliable as in they are mostly not emitted but sometimes are emitted.

Events from a smart contract (Gnosis Safe contract, SignMsg but true for other events as well) events usually are not being emitted through **ethers** on **optimism** even though I can see they are actually emitted from the contract on etherscan. I'm using Alchemy as the RPC provider and it seems there are no outages or rate limiting on there as well.

In the below code, you can see how i wait for the events.

This only happens on Optimism. Goerli works perfectly fine.

I'm curious why this piece of code fails to receive the events sometimes. Any clue or suggestion is appreciated 🙏🙏🙏

Thanks in advance.

Code Snippet

const waitSmartContractSignature = async (signer: Signer, hash: string) => {
    const walletContract = new Contract(await signer.getAddress(), EIP1271.abi, signer)
    const internalHash = await walletContract.getMessageHash(hash)
    const eventFilter = walletContract.filters.SignMsg(internalHash)
    return await resolveOnContractEvent(walletContract, eventFilter)
}

const resolveOnContractEvent = (contract: Contract, eventFilter: EventFilter) =>
    new Promise<void>((resolve, reject) => contract.once(eventFilter, resolve).once('error', reject))

### Contract ABI

```shell
{
    "abi": [
        {
            "anonymous": false,
            "inputs": [
                {
                    "indexed": true,
                    "internalType": "bytes32",
                    "name": "msgHash",
                    "type": "bytes32"
                }
            ],
            "name": "SignMsg",
            "type": "event"
        },
        {
            "inputs": [
                {
                    "internalType": "bytes",
                    "name": "message",
                    "type": "bytes"
                }
            ],
            "name": "getMessageHash",
            "outputs": [
                {
                    "internalType": "bytes32",
                    "name": "",
                    "type": "bytes32"
                }
            ],
            "stateMutability": "view",
            "type": "function"
        },
        {
            "inputs": [
                {
                    "internalType": "bytes",
                    "name": "_data",
                    "type": "bytes"
                }
            ],
            "name": "signMessage",
            "outputs": [],
            "stateMutability": "nonpayable",
            "type": "function"
        },
        {
            "constant": true,
            "inputs": [
                {
                    "internalType": "bytes32",
                    "name": "_hash",
                    "type": "bytes32"
                },
                {
                    "internalType": "bytes",
                    "name": "_signature",
                    "type": "bytes"
                }
            ],
            "name": "isValidSignature",
            "outputs": [
                {
                    "internalType": "bytes4",
                    "name": "",
                    "type": "bytes4"
                }
            ],
            "payable": false,
            "stateMutability": "view",
            "type": "function"
        }
    ]
}

Errors

No response

Environment

Browser (Chrome, Safari, etc)

Environment (Other)

optimism, alchemy

[nobrayner]

Just noting that I have been experiencing similar issues - events being created on chain, but not triggering my event listeners - also with Alchemy, but on the Arbitrum Testnet.

My situation also differs in that I am calling contract.on, and not contract.once.

Further findings:

• Sometimes restarting the process fixes it, and it starts receiving new events
• After periods of not working, it starts working again

---

My conclusion is that it is something to do with Alchemy more than ethers, but I am not sure how to proceed with testing/verification.

[goerris]

Hey!
I'm also experiencing the same issue on Polygon Mainnet.
"ethers": "^5.7.1",
I am using Alchemy as a provider and pretty often the events won't trigger.
Calling contract.on.

Saw that a very similar issue was addressed on 2652
And supposedly fixed on v5.6.0 ...

[panukettu]

Since most rollups consider every transaction as a "block" it might be that the default value for provider.pollingInterval is missing transactions as a single poll round seems to do a eth_getLogs for the newest 10 blocks.

Related #3599

[unek]

having the same issue. running off my own Optimism node.

[ricmoo]

Can you please update to the latest version? Similar problems were addressed since the version your OP indicated you were on. :)

[unek]

I am on 5.7.2.

[unek]

my issue might not be ethers-related, I see that I'm stuck on block number 67766754, whatever the fuck that number is

[Siegrift]

Since most rollups consider every transaction as a "block" it might be that the default value for provider.pollingInterval is missing transactions as a single poll round seems to do a eth_getLogs for the newest 10 blocks.

Is this correct? I wasn't able to find this logic in ethers implementation, but I can confirm this for Hardhat. I created an event listener and made 20 transactions. But I only received 10 events via the listener.

[unek]

@Siegrift have you tried using the websocket provider?

[ricmoo]

A polling provider searches ranges, not individual blocks (so if during the last poll it ended on block 1000 and the current poll it is block 1016, it will search blocks 1001 through 1016, inclusive).

[ricmoo]

(It also maintains a sliding window, with capped end-points, to account for networks with fast block times that do not index events before emitting block numbers)