Re: [pve-devel] [RFC many 0/3] combine and simplify RRD handling

[Thomas Lamprecht <t.lamprecht@proxmox.com>]

Am 05.09.25 um 10:03 schrieb Aaron Lauterer:
> 
> 
> On  2025-09-04  20:20, Thomas Lamprecht wrote:
>> Am 04.09.25 um 16:09 schrieb Aaron Lauterer:
>>> this series does two things:
>>> * switch the RRD API backend to use the old RRD files is available
>>> * always use RRD files with the new 9.0 schema
>>>
>>> The motivation for the combination of old and new RRD files is that during the
>>> migration of old RRD files to the new ones, spikes get flattened. By combining
>>> the old and new RRD files, we can keep the old coarse data with all it spikes
>>> and only show the new much mode finer stepped data where available.
>>>
>>> This will also enable us to just write any new data into an RRD file that is
>>> created with the new 9.0 schema. As a result, no migration step is needed
>>> anymore and we can simplify the logic around the whole "does the only the old
>>> file exist or is the new one also present" alot in quite a few places.
>>>
>>> Some examples which we can simplify or revert:
>>> pve-manager: API2Tools::get_rrd_key can most likely be dropped
>>> qemu-server, pve-storage, pve-container,…: rrd API endpoints which check which files exist
>>> drop the whole migration step on upgrade
>>>
>>> other TODOs:
>>>
>>> RRD::create_rrd_graph -> see if we can combine both files into one graph. But we
>>> are relying on RRD itself for this. So that might be interesting. On the other
>>> hand, do we want to keep that API endpoint around? People are using it though.
>>> So we need to weigh that decision accoringly.
>>
>> Keeping it around for the time being is definitively required now that
>> PVE 9.0 is out, we might sunset it for a future major release.
>>
>> Another option might be to generate both images and merge them manually,
>> i.e. literally make the right part the old and the left part the new
>> image with some imagemagick command. Or does rrd indeed supports merging
>> two files together?
> 
> One thing that should be possible is to give it two datasets from different files. That would be a middle ground as in, all data is there, but it would show up as separata data lines.
> 
> I am looking into it to see if we could get it nicer. Manually stitching images together will most likely not work because I don't expected the scales to match up perfectly.

True w.r.t. not matching scales. But as one can override the line colors we could probably just do that and use the same ones for both data series?


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