Debugging parasDisputes

Question

We noticed on Jan 19 that kintsugi (our kusama para) did not finalize blocks for about 60 minutes. It seems the cause is likely rooted in disputes being raised. In turn, a lot of dispute events fired on kusama: https://kusama.subscan.io/event?module=parasdisputes&event=all&page=1&address=&startDate=&endDate=&startBlock=&endBlock=&timeType=date&version=9360

I'm not too familiar with disputes and was wondering if anyone might be able to help:

• Were other paras affected as well, or were all of the disputes coming from kintsugi? The event does not include the para id, so I'm not sure how one would verify which paras (if any other than kintsugi) were affected
• How would we figure out what caused the dispute in the first place? We did not run any runtime upgrade. We do have community-run collators, so they might run a patched/changed version of our collator nodes

Answer 1

Disputes get triggered, if some validator thinks that a parachain block is invalid. It does not really matter for the outcome which parachain's block was triggering the dispute, what happens is the following:

1. All validators check ... so there is more load on the network, which can slow down parachain consensus.
2. Finality is halted until disputes are resolved.

All parachains should be affected rather similarly, no matter what parachain blocks got disputed.

About the cause, we are contacting the disputing validators to figure it out. It very likely has nothing to do with the parachain itself ... because then the dispute would likely resolve against the candidate and the relay chain would revert, which to my knowledge did not happen. If the dispute resolves in favor of the candidate, then the candidate is fine, it is just that some validator has some problem, making it believe the candidate is invalid. E.g. disk corruption.