Xline is a geo-distributed KV store for metadata management. It provides the following features:

• Etcd compatible API.
• Geo-distributed friendly deployment.
• Compatible with K8s.

With the wide adoption of cloud computing, multi-cloud has become the mainstream IT architecture for enterprise customers. Multi-cloud (or similarly multi-datacenter), however, obstacles data access across different cloud (or data center) providers to some extent. Further, data isolation and data fragmentation resulting from cloud barriers have become impediments to business growth. The biggest challenge of multi-datacenter architecture is how to maintain strong data consistency and ensure high performance in the race condition of multi-datacenter scenario. Traditional single datacenter solutions cannot meet the availability, performance, and consistency requirements of multi-data center scenarios. This project targets the multi-datacenter scenario, aiming to realize a high-performance multi-cloud metadata management solution, which is critical for businesses with geo-distributed and multi-active deployment requirements.

Cross-datacenter network latency is the most important factor that impacts the performance of geo-distributed systems, especially when a consensus protocol is used. We know consensus protocols are popular to use to achieve high availability. For instance, Etcd uses the Raft protocol, which is quite popular in recently developed systems.

Although Raft is stable and easy to implement, it takes 2 RTTs to complete a consensus request from the view of a client. One RTT takes place between the client and the leader server, and the leader server takes another RTT to broadcast the message to the follower leaders. In a geo-distributed environment, an RTT is quite long, varying from tens of milliseconds to hundreds of milliseconds, so 2 RTTs are too long in such cases.

We adopt a new consensus protocol named CURP to resolve the above issue. Please refer to the paper for a detailed description. The main benefit of the protocol is reducing 1 RTT when contention is not too high. As far as we know, Xline is the first product to use CURP.

We compared Xline with Etcd in a simulated multi-cluster environment. The details of the deployment is shown below.

We compared the performance with two different workloads. One is 1 key case, the other is 100K key space case. Here's the test result.

It's easy to tell Xline has a better performance than Etcd in a geo-distributed multi-cluster environment.

Please refer to the Contribute Guide for the quick start guide.

• v0.1 ~ v0.2
  • Support all major ETCD APIs
  • Pass validation tests
• v0.3 ~ v0.5
  • Enable persistent storage
  • Enable snapshot
  • Enable cluster membership change
• v1.0 ~
  • Enable chaos engineering to validate the system's stability
  • Integration with other CNCF components