Kenshin

Kenshin (るろうに剣心)

Kenshin project consists of two major components:

• Kenshin is a fixed-size time-series database format, similar in design to Whisper, it's an alternative to Whisper for Graphite storage component. Whisper performs lots of tiny I/O operations on lots of different files, Kenshin is aiming to improve the I/O performance. For more design details please refer to design docs (Chinese) and QCon 2016 Presentation slide.

• Rurouni-cache is a storage agent that sits in front of kenshin to batch up writes to files to make them more sequential, rurouni-cache is to kenshin as carbon-cache is to whisper.

Kenshin is developing and maintaining by Douban Inc. Currently, it is working in production environment, powering all metrics (host, service, DAE app, user defined) in douban.com.

What's the performance of Kenshin?

In our environment, after using Kenshin, the IOPS is decreased by 97.5%, and the query latency is not significantly slower than Whisper.

Quick Start

We recommend using virtualenv when installing dependencies:

$ git clone https://github.com/douban/Kenshin.git
$ cd Kenshin
$ virtualenv venv
$ source venv/bin/activate
$ pip install -r requirements.txt

Tests can be run using nosetests:

$ nosetests -v

Setup configuration

$ misc/init_setup_demo.sh

Setup Kenshin

$ python setup.py build_ext --inplace && python setup.py install

Start two rurouni-cache instances

$ python bin/rurouni-cache.py --debug --config=conf/rurouni.conf --instance=0 start
$ python bin/rurouni-cache.py --debug --config=conf/rurouni.conf --instance=1 start

Then go to Graphite-Kenshin for starting Web instances.

FAQ

Why don't you just use whisper?

Whisper is great, and initially we did use it. Over time though, we ran into several issues:

1. Whisper using a lot of IO. There are serval reasons:
   • Using one file per metric.
   • Realtime downsample feature (different data resolutions based on age) causes a lot of extra IO
2. Carbon-cache & Carbon-relay is inefficient and even is cpu-bound. We didn't write our own carbon-relay, but replaced carbon-relay with carbon-c-relay.

Why did you totally rewrite whisper? Couldn't you just submit a patch?

The reason I didn't simply submit a patch for Whisper is that kenshin's design is incompatible with Whisper's design. Whisper using one file per metric. Kenshin on the other hand merge N metrics into one file.

How to intergrate Kenshin with Graphite-Web?

We use write a plugin for Graphite-API named Graphite-Kenshin

Acknowledgments

• Thanks for the Graphite project.
• Thanks to @grobian for the carbon-c-relay project.

Contributors

• @zzl0
• @mckelvin
• @windreamer
• @youngsofun
• @camper42

License

Kenshin is licensed under version 2.0 of the Apache License. See the LICENSE file for details.