Contract events arrive slower

[benjaminaaron]

I noticed that receiving contract events via .on() takes consistently longer than it takes drizzle or web3 to receive the same events. Does it wait for more confirmations or is there a polling rate that is set to lower by default? Can I speed this up somehow? 🚀

[ricmoo]

What backend are you using?

Which event? An Event filter is emitted once it is minded in a block, so it shouldn't matter. But if your backend is something like Ganache, it may be slower than it needs to be, since Ganache mines "instantly" and the polling providers do only poll every 4 seconds (by default).

If you are connecting to ganache, you can likely increase the polling rate (by setting the provider.pollingInterval to a lower number, in ms; default is 4000).

If you are using something like INFURA though, setting this number lower will likely result in your queries getting heavily throttled.

[benjaminaaron]

Thanks for your response. I am using the MetaMask extension on Chrome desktop and the MetaMask mobile app on Android. For both Ganache locally as well as a deployment on Rinkeby (dev.finfour.net, using INFURA) I noticed that ethers.js is slower to receive my TestEvent. This is how I subscribe to the event, is that correct?

[benjaminaaron]

Hi @ricmoo, a related question. Let me know if I should open a new issue for this.
When I subscribe to a contract event, the first thing it does is receive the last event that was fired - before I subscribed though. Is there a way I can ensure only events are received that are emitted after I subscribed to them?

[ricmoo]

You can use provider.once("block", () => { provider.on(event, handler); }), which will what for the next block before subscribing.

I will probably make v6 only return events starting after the current block, but this is not a change that can be made in v5.