eth_estimateGas produces an incorrect value when run multiple times in parallel

[nuevoalex]

System information

Geth version: Version: 1.7.3
OS & Version: Alpine Linux v3.7
Commit hash : 4bb3c89d44e372e6a9ab85a8be0c9345265c763a

Expected behavior

Calls to estimateGas return a deterministic amount that is sufficient to run the estimated transaction.

Actual behavior

Making many eth_estimateGas calls running in parallel for the same transaction will in rare cases return an anomalous value that is less than the gas required for the transaction to succeed.

Steps to reproduce the behavior

Upload this contract:

contract TestContract {
    bool private flag;

    function test() public {
        flag = true;
    }
}

Now using curl run several (10 worked with just a couple attempts) gas estimate requests in parallel with the relevant data filled in as appropriate for your setup:

curl -X POST --data '{"jsonrpc":"2.0","method":"eth_estimateGas","params":[{"from": "0xfromaddess", "to": "0xcontractaddresss", "data": "0xf8a8fd6d"}], "id": 1}' --url http://localhost:port -H "Content-Type: application/json" & ... & ...

The results should come back identical, however after a few attempts you will get something like this:

{"jsonrpc":"2.0","id":1,"result":"0x682b"}
{"jsonrpc":"2.0","id":1,"result":"0x682b"}
{"jsonrpc":"2.0","id":1,"result":"0x682b"}
{"jsonrpc":"2.0","id":1,"result":"0x682b"}
{"jsonrpc":"2.0","id":1,"result":"0x682b"}
{"jsonrpc":"2.0","id":1,"result":"0x682b"}
{"jsonrpc":"2.0","id":1,"result":"0x682b"}
{"jsonrpc":"2.0","id":1,"result":"0x6821"}

Note that the last response is incorrect.

Worth noting in the actual node setup is that we are using 1 second block times.

[stale]

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