A Highly-Available Move Operation for Replicated Trees

Replicated tree data structures are a fundamental building block of distributed filesystems, such as Google Drive and Dropbox, collaborative applications with JSON or XML model. These systems need to support move operation that allows subtree be moved new location within the tree. However, move is difficult implement correctly if different replicas can concurrently perform arbitrary operations, we demonstrate bugs in Dropbox arise concurrent moves. In this article present CRDT algorithm handles modifications on trees, while ensuring structure remains valid (in particular, no cycles introduced), guaranteeing all converge towards same consistent state. Our requires synchronous coordination between replicas, making it highly available face network partitions. We formally prove correctness our using Isabelle/HOL proof assistant, evaluate performance verified implementation geo-replicated setting.