Fast Optimistic Concurrency Control with Apache Ozone S3 Conditional Requests
Apache Ozone will support conditional PutObject, GetObject, HeadObject, CopyObject, and CompleteMultipartUpload in the upcoming 2.2 release (RC0 is currently under a vote), and will add conditional DeleteObject and DeleteObjects support in 2.3.
An increasing number of database systems are moving storage to S3 in shared-everything architectures to reduce cost, dependencies, and operational complexity. In the Hadoop 🐘 era, we typically used ZooKeeper and HDFS as the control plane and data plane. Modern systems are moving the control plane to self-managed consensus groups or RDBMS-backed catalogs, while moving the data plane onto AWS S3 or S3-compatible storage.
Shared-everything systems usually have two pain points: communication overhead and coordination. To reduce write latency, systems often use inline data writes, background flush, and LSN-based union reads. To reduce read latency, they add multi-layer caches, such as self-managed or OS-managed in-memory caches and on-disk caches. Coordination is harder: multiple clients may read the same metadata, make decisions locally, and then try to update the same object. Without a storage-level compare-and-set primitive, applications often need an external lock service, catalog database, or consensus system just to avoid lost updates.
Because Apache Ozone exposes S3, HCFS, HttpFS, and Java APIs as part of its multi-protocol story, conditional requests have become increasingly important. This work is now nearly complete.
