Gnocchi 3.0 release

Monday 03 October 2016 Gnocchi, OpenStack Comments

After a few weeks of hard work with the team, here is the new major version of Gnocchi, stamped 3.0.0. It was very challenging, as we wanted to implement a few big changes in it.

Gnocchi is now using reno to its maximum and you can read the release notes of the 3.0 branch online. Some notes might be missing as it is our first release with it, but we are making good progress at writing changelogs for most of our user facing and impacting changes.

Therefore, I'll only write here about our big major feature that made us bump the major version number.

New storage engine

And so the most interesting thing that went in the 3.0 release, is the new storage engine that has been built by me and Gordon Chung during those last months. The original approach of writing data in Gnocchi was really naive, so we had an iterative improvement process since version 1.0, and we're getting close to something very solid.

This new version leverages several important features which increase performance by a large factor on Ceph (using write(offset) rather than read()+write() to append new points), our recommended back-end.

read+write (Swift and file drivers) vs offset (Ceph)

To summarize, since most data points are sent sequentially and ordered, we enhanced the data format to profit from that fact and be able to be appended without reading anything. That only works on Ceph though, which provides the needed features.

We also enabled data compression on all storage drivers by enabling LZ4 compression (see my previous article and research on the subject), which obviously offers its own set of challenges when using append-only write. The results are tremendous and decrease data usage by a huge factor:

Disk size comparison between Gnocchi 2 and Gnocchi 3

The rest of the processing pipeline also has been largely improved:

Processing time of new measures
Compression time comparison

Overall, we're delighted with the performance improvement we achieved, and we're looking forward making even better more progress. Gnocchi is now one of the most performing and scalable timeseries databases out there.

Upcoming challenges

With that big change done, we're now heading toward a set of more lightweight improvements. Our bug tracker is a good place to learn what might be on our mind (check for the wishlist bugs).

Improving our API features and offering a better experience for those coming outside of the real of OpenStack are now on my top priority list.

But let me know if there's anything you have scratching you, obviously. 😎