[openstack-dev] Concerns about Gnocchi's performance

Julien Danjou julien at danjou.info
Thu Jan 15 10:46:33 UTC 2015

On Thu, Jan 15 2015, 张灿 wrote:


> I noticed in the code, every time a measure gets updated, gnocchi first reads
> all the previous contents of that measure, updates the measure in memory and
> writes the updated contents as well as original contents back. IMHO, the
> overhead here could be very large. As an improvement, I propose we use some
> form of `seek` that only modifies the updated parts.

Yep, that's the main downside of the use of the Carbonara based backend
in Gnocchi. But honestly, since it's download/upload are parallel and
the file size is quite small, sending a metric should be pretty fast in
most circumstances. Though that's sure it's gonna be faster with
backends where you just have to send the actual metrics (OpenTSDB or
InfluxDB likely).

> So I’d like to hear about your opinions, and if there’s already a
> solution, please point it to me.

I'd love to improve the backends you describe with some sort of `seek'
solution, unfortunately I don't think it'll be possible to do so using
Swift. Though it might be possible to do so using Ceph and the file
based backends, so maybe it'd be worth looking at that. Any help

Julien Danjou
# Free Software hacker
# http://julien.danjou.info
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