SIM-BE Some transactions in the consensus queue get duplicated, potentially resulting in stuck processing

[denishacquin]

When submitting many transactions, it happens that they get stuck on pending.

When checking the backend logs, I see some errors:

~ ~ ~ ~ ~ TRANSACTION ALREADY IN PROCESS

And when printing the queued tx IDS and status in the backend, I see that many transactions apparently get added multiple times to the queue, not sure if this is expected:

Step to reproduce:

• Spam write transactions to a contract from the simulator

Restarting the backend clears the clone-filled queue and gets the process unstuck.

[denishacquin]

Is this expected @cristiam86 @AgustinRamiroDiaz ?

Otherwise,see linked branch for a fix proposal.

The idea would be to avoid duplicates by checking if the tx ID exists in the queue first, and keeping track of processed txs.

[cristiam86]

Oh, yes, the transaction shouldn't be re-inserted in the queue. This could be fixed when we implement the nonce, it is the purpose of that field

[AgustinRamiroDiaz]

This is highly related to #387. There was a patch done to print the TRANSACTION ALREADY IN PROCESS and not try to re-execute it.

The idea would be to avoid duplicates by checking if the tx ID exists in the queue first, and keeping track of processed txs.

This is an almost perfect solution, but there's a small race condition that could happen where:

• the consumer pops the transaction from the queue to start consuming it
• the loop checks for the transaction in all queues, and doesn't find it so it adds it

It would be a great improvement for 99% of the cases, so maybe it's a good idea to also add that patch

To make it 100% reliable I think we'll probably need to add some kind of synchronization between the 2 threads, like a lock or something

[cristiam86]

We should implement the same blockchain approach, if there is a transaction with that nonce, it get's rejected.

[denishacquin]

let's wait for transaction hashes #479 and nonces #468 , which should help resolving this issue