XLS-56d: Atomic/Batch Transactions

[mvadari]

Discussion thread can be found here: #162

This PR will be left open for easier commenting of specific lines/sections. The discussion will also still be available for ease of commenting for non-technical people.

[mDuo13]

I am somewhat concerned about the greater potential for front-running with batch transactions. It seems like that is the "use case" that receives the biggest direct benefit from this feature even though we would rather discourage front-running.

Related, I think the specification should make it explicit how the batch affects the canonical order of transactions. It seems like the intent is for the canonical order to contain the outer transaction followed by the successful inner transactions in direct sequence, and that would start from wherever the outer transaction gets placed in the canonical order?

It might also be worth adding a subsection to Security about transaction fees. Specifically, make a note about how the outer transaction pays fees for all the inner transactions even if using modes like ONLYONE where some of those transactions can fail, and how this is a precaution against exploits that could make the whole network do the work of processing candidate transactions that won't pay transaction fees.

[ckeshava]

What's the influence of Batch transactions on the open-ledger cost? For instance, if 10 Batch transactions are included in a validated ledger, this is equivalent to inserting at most 80 non-Batch "usual" transactions. Is the soft-limit of the open-ledger cost calculation proportionately increased by this amendment?

[mvadari]

What's the influence of Batch transactions on the open-ledger cost? For instance, if 10 Batch transactions are included in a validated ledger, this is equivalent to inserting at most 80 non-Batch "usual" transactions. Is the soft-limit of the open-ledger cost calculation proportionately increased by this amendment?

The open-ledger cost is tied to the total fee of all the Batch transactions, on the outer transaction.