Unclaimed gas calculation incorrect about neo-python HOT 6 CLOSED

I think failure would make sense if the total gas to claim suggested by neo-python is bigger than what the others think, but smaller shouldn't fail. A wrong total value is still an issue of course.

I have to let this one sink in for a moment. I've been working on neo3 for a while now that I have to refresh my mind on the 2.x code base and UTXO model.

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I think it will be hard for me to debug anything given that it is a claim on your account. My first idea is to compare the unclaimed returned here

with what the C# client would say here (make sure to not accidentally relay the transaction on the C# side)
https://github.com/neo-project/neo/blob/54d0f29c82fc38b4af7d7d2df05e4e564e7966dd/neo/Persistence/Snapshot.cs#L35

Comparing start height, end height and output value. If there is no difference there, then it must be somewhere here

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OK, I have tracked the issue down to GetSysFeeAmountByHeight. The end block height for this transaction is 5028923. I checked the expected fee via JSON-RPC, and it's supposed to be 307291. The value being returned by neo-python is 27399.

When I manually run the rest of the GAS calculation with the proper/expected value, it does result in the proper GAS amount, so this is definitely the issue.

I'm going to see if I can get a new chain DB to see if it's just my local DB being out-of-whack that's the issue.

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I checked a different fully sync'd neo-python chain, and it has the same issue.

@ixje, do you have a neo-python 2.0 chain you can test against? I'm just using the RPC server to quickly test:

np-api-server --mainnet --port-rpc 8099

With the JSON-RPC call:

curl -H 'Content-Type: application/json' -d '{"jsonrpc":"2.0","method":"getblocksysfee","params":[5028923],"id":1234}' http://localhost:8099

Expecting a value of 307291 but getting a value of 27399.

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@ixje, do you have a neo-python 2.0 chain you can test against?

I unfortunately have to say no. I used to have a VPS running the latest version for audit reasons but that seems to have died and I've not been able to recover it (yet). The fastest option I can think of is taking a neo-python bootstrap 4117000 and the latest available chain.acc from NGD and using np-import to sync back up (something like np-import -m -a -i chain.acc --datadir <root folder containing "Chains/Main/">).

iirc the neo-python bootstrap was made with 0.9.1. That should be the fastest route to checking if it's a local chain issue or not.

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It worked! 🎉 I did a full re-sync, starting from @ixje's bootstrap, syncing with chain.acc, and then syncing the last 200k blocks in np-prompt (which took over a week in total 😳). The gas calculations that resulted from the full rebuild were correct and solved the issue.

Thanks, @ixje! Glad to hear neo-python had it right; once I saw your confidence that it should work, I was very hopeful that's all it would be 👍

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