Summary

The data structure mempoolIDs in the mempool reactor is used to assign a unique identifier of type uint16 to each peer (identified by p2p.ID). These ids are only known locally to the node, and only used to keep track of the senders of each transaction.

PR tendermint/tendermint#2778 introduced this data structure, where it says: "Instead of using the 20byte peer ID, it instead uses a local map from peerID to uint16 counter, so every peer adds 2 bytes. (Word aligned to probably make it 8 bytes)".

Proposal

Remove mempoolIDs that is only used to save 12 bytes per connected peer.

See original discussion: #1043 (comment)