FlowG – Distributed Systems without raft (part 2)

Eventual Consistency As said in the original article, we chose for FlowG to be eventually consistent. We initially planned to use an “operation log” and Conflict-free Replicated Data Types (CRDTs) to implement the replication part. This idea was temporarily dismissed. I’ll explain why. Our storage backend is BadgerDB: It is an embeddable key/value database with full transaction support. Internally, it uses a Log Structured Merge Tree (LSM) to organize key/value pairs. Every key/value pair is assigned a “version”, and every mutation on a key updates that version. This enables incremental backups quite easily: nextSince, err := db.Backup(writer, since) nextSince, err = db.Backup(writer, nextSince + 1) // ... This also means that we don’t actually need an “operation log” to track the mutations done on a database. As for the CRDT, FlowG has 3 kinds of storages: auth: stores users, permissions, tokens, roles, … stores users, permissions, tokens, roles, … config: stores configura ... Read full article.