Mempool

The economic protocol provides a protocol-side mempool module data structure intended for use by the shell prevalidator (see The Prevalidator) and by octez-baker to incrementally accumulate operations that can be safely used to bake a new block.

It ensures that :

• Every operation contained are valid;

• every operation are co-valid: they can be safely included in a block in any arbitrary order, meaning operations commute;

• the merging of two mempools also maintains the aforementioned properties.

The protocol leverages the partial construction mode to incrementally validate new operations while maintaining the aforementioned invariants.

During validation, operations are never actually applied, as it is unnecessary for asserting their validity.

Merging Mempools

The protocol-side mempool data structure is designed to allow the merging of two mempools. This is useful in practice when injecting an external mempool into the current one. The design also considers the future possibility of parallelizing operations validation and then merging mempools in a divide-and-conquer style, an approach that could be implemented later to accelerate validation.

Conflict

Of course, two mempools containing conflicting operations cannot be merged while maintaining the desired invariants. Similarly, if an injected operation conflicts with existing ones, the properties would not hold. To solve conflicts, the structure requires a conflict_handler, a function called upon encountering conflicts to determine which operation remains and which is discarded.