XiaoMi/pegasus

A distributed key-value storage system developed and maintained by Xiaomi Cloud Storage Team.


repo name	XiaoMi/pegasus
repo link	https://github.com/XiaoMi/pegasus
homepage	https://pegasus-kv.github.io/
language	C++
size (curr.)	32739 kB
stars (curr.)	1173
created	2015-09-01
license	Apache License 2.0

Note: The master branch may be in an unstable or even broken state during development. Please use releases instead of the master branch in order to get stable binaries.

Pegasus is a distributed key-value storage system which is designed to be:

horizontally scalable distributed using hash-based partitioning
strongly consistent: ensured by PacificA consensus protocol
high-performance: using RocksDB as underlying storage engine
simple: well-defined, easy-to-use APIs

Pegasus has been widely-used in XiaoMi and serves millions of requests per second. It is a mature, active project. We hope to build a diverse developer and user community and attract contributions from more people.

Background

HBase was recognized as the only large-scale KV store solution in XiaoMi until Pegasus came out in 2015 to solve the problem of high latency of HBase because of its Java GC and RPC overhead of the underlying distributed filesystem.

Pegasus targets to fill the gap between Redis and HBase. As the former is in-memory, low latency, but does not provide a strong-consistency guarantee. And unlike the latter, Pegasus is entirely written in C++ and its write-path relies merely on the local filesystem.

Apart from the performance requirements, we also need a storage system to ensure multiple-level data safety and support fast data migration between data centers, automatic load balancing, and online partition split.

After investigating the existing storage systems in the open source world, we could hardly find a suitable solution to satisfy all the requirements. So the journey of Pegasus begins.