change(mempool): Return verification result after attempting to insert transactions in the mempool

arya2 commented 1 month ago

Motivation

We want to return a verification result from the mempool after a transaction has been inserted into its verified set (or has failed some final checks in the mempool).

Solution

Moves timeout from mempool to mempool's Download struct
Sends the final result to the response channel after attempting to insert a transaction into the mempool storage instead of after a transaction is successfully verified

Tests

Updates the mempool_responds_to_await_output test to expect the mempool storage to include a transaction immediately after receiving its verification result.

PR Author's Checklist

[x] The PR name will make sense to users.
[ ] The PR provides a CHANGELOG summary.
[x] The solution is tested.
[x] The documentation is up to date.
[x] The PR has a priority label.

PR Reviewer's Checklist

[ ] The PR Author's checklist is complete.
[ ] The PR resolves the issue.

mpguerra commented 1 month ago

Is there a related issue for this PR?

arya2 commented 1 month ago

Is there a related issue for this PR?

Zebra began returning errors from the sendrawtransaction RPC method when verifying the transaction fails or was cancelled in https://github.com/ZcashFoundation/zebra/pull/8788, but in one of the tests for https://github.com/ZcashFoundation/zebra/pull/8857, we noticed that it sends the success response too early because:

There are duplicate spend and mempool size checks that could still fail, or
Re-verifying the transaction could fail if the chain tip changes during verification and the update best chain spends or reveals relevant outputs or nullifiers.

mpguerra commented 4 days ago

Do we still want to do this one? Otherwise we should just close for now

ZcashFoundation / zebra