listunspent issues

[obycode]

There are two problems with the miners calls to listunspent:

stacks-core/testnet/stacks-node/src/burnchains/bitcoin_regtest_controller.rs

Lines 2619 to 2630 in b5250c6

	let payload = BitcoinRPCRequest {
	method: "listunspent".to_string(),
	params: vec![
	min_conf.into(),
	max_conf.into(),
	addresses.into(),
	include_unsafe.into(),
	json!({ "minimumAmount": minimum_amount, "maximumCount": config.burnchain.max_unspent_utxos }),
	],
	id: "stacks".to_string(),
	jsonrpc: "2.0".to_string(),
	};

We added the maximumCount option to ensure that the response is not too large, because the HTTP library can only handle messages up to 16MB.

Problem 1

If we hit this limit, the bitcoind will return UTXOs oldest first. A miner's block commit needs to use the output of the previous block commit, so this will be a very recent UTXO, so it may be pruned from the results. This is a problem.

Problem 2

It seems that this option will not actually make it return maximumCount UTXOs. In a test in the nakamoto-3 network, if I call listunspent without this limit, it returns 2513 UTXOs, but then when I call it with the maximumCount set to 1024, it returns 365 UTXOs.

[obycode]

To avoid problem 1, @kantai's suggestion:

Yeah, realistically, the miner should always spend its last commit’s UTXO
And add another input if necessary

We can make this change with low priority.