The mempool module

The mempool module provides mempool implementations for the Flow blockchain, which are in-memory data structures that are tasked with storing the flow.Entity objects. flow.Entity objects are the fundamental data model of the Flow blockchain, and every Flow primitives such as transactions, blocks, and collections are represented as flow.Entity objects.

Each mempool implementation is tasked for storing a specific type of flow.Entity. As a convention, all mempools are built on top of the stdmap.Backend struct, which provides a thread-safe cache implementation for storing and retrieving flow.Entity objects. The primary responsibility of the stdmap.Backend struct is to provide thread-safety for its underlying data model (i.e., mempool.Backdata) that is tasked with maintaining the actual flow.Entity objects.

At the moment, the mempool module provides two implementations for the mempool.Backdata:

• backdata.Backdata: a map implementation for storing flow.Entity objects using native Go maps.
• herocache.Cache: a cache implementation for storing flow.Entity objects, which is a heap-optimized cache implementation that is aims on minimizing the memory footprint of the mempool on the heap and reducing the GC pressure.

Note-1: by design the mempool.Backdata interface is not thread-safe. Therefore, it is the responsibility of the stdmap.Backend struct to provide thread-safety for its underlying mempool.Backdata implementation.

Note-2: The herocache.Cache implementation is several orders of magnitude faster than the backdata.Backdata on high-throughput workloads. For the read or write-heavy workloads, the herocache.Cache implementation is recommended as the underlying mempool.Backdata implementation.