when uncle block info is recorded into blockchain irreversibly?

Question

I want to confirm that what time is proper for checking there is uncle block or not.

I know that eth_getUncleCountByBlockNumber returns # of uncle blocks at a block number. (max is 2)

But when considering how ethereum handle uncle block, I think the timing of calling the method is very important.

For example, let's assume that latest block number of ethereum now is 20,000,000. And if I call the method at that moment, it returns 0 even if there may be uncle block in the future.

So which timing is safe for getting uncle block count in terms of confirmation?

Is it safe when I call the method with a block number of which confirmations is >= 12??

Answer 1

Nothing is ever 100% certain with Ethereum blockchain, it's all about probabilities. In theory every single block after the genesis block could still be reverted and a new canonical chain created.

That's exactly why many entities use this concept of "confirmations". The number of confirmations means how many blocks are mined successfully on top of the block in question. The more confirmations there are the more likely it is that the block will not be reverted anymore (and uncles won't change). But the more confirmations you wait for the slower your actions become because you have to wait the same amount of confirmations for every transaction.

The exact amount of confirmations you wait for depends on you. 12 confirmations is a pretty safe amount. Looking at https://ethereum.stackexchange.com/a/73007/31933 even a reorganization 3 blocks deep is very rare.