Hi all,
Following on from Bernard's & Brad's emails, here's my wish-list for 3.1.0
(although some ideas are perhaps for a more longer-term).
Gathering of metrics:
o A cleaner XDR encoding:
The current encoding scheme embeds too much information about which
metrics
gmond collects. The encoding scheme should treat all metrics the same:
as
just "a metric". The encoding should not care if the metric is
metric_cpu_speed, metric_swap_total or a user-defined "gmetric" one.
o Metric packing:
Simply that a UDP packet can contain multiple metrics (using the usual
XDR
stream decoding) up to the size of a UDP packet. This would help reduce
the overheads when sending many metric updates concurrently. It also
preserves the current gmond behaviour where it sends metric updates in
a single UDP packet.
o Support for counters (metrics with +ve slope)
This shouldn't require much work (from memory, make sure the slope-type
information is preserved and patch gmetad to create RRD files with the
correct options). Currently Ganglia doesn't actually support custom
counter metrics, which is an awkward limitation.
o gmond switching to a non-blocking IO model.
If there's a large number of metric updates then gmond must process them
"quickly" or they will be lost. If this happens whilst gmond is
sending XML
data to gmetad there's may be a delay, increasing the risk of metric
update messages being lost. Switching to a non-blocking IO model would
allow
gmond to respond preferentially to the incoming UDP messages.
o Brad's "alias" idea.
Yes, great idea; although I'd call it "title", "description" (or "short
description") rather than "alias" --- but that's just the name for the
thing.
o Flexible method of adding extra metric metadata.
We could include extra metadata, not just "alias"/"title". For
example, some
metrics have a natural minimum and maximum value. Perhaps coming up
with an
extendable way of encoding metric metadata so future changes can be
included
without loosing backwards compatibility.
Web interface:
o Better icons.
The current highly-compressed JPEG files for the icons look horrible!
Line-art perhaps suffers worst from JPEG compression artifacts. Could
we not
use either PNGs or (preferably) SVG?
o Add an option to allow switching to SVG in-line RRDTool graphs.
This should be pretty easy to add as a config option. I think support
for
SVG in current browsers is now "good enough". A half-way modern
version of
RRDTool can generate SVG versions of the graphs, which should look much
better.
o Have some standard way of describing custom graphs.
There currently isn't a standard way of producing custom graphs;
"custom"
here means adding support for host-specific and cluster-specific graphs
and
also some framework for describing those custom graphs. I have a
solution, that (at least) has merit in both existing and working.
Perhaps it
isn't ideal, but the Ganglia web front-end should provide at least some
standard hooks if not an actual framework.
o Have the option to switch off displaying all the single-metric graphs.
If you have ~300 metrics, the little graphs at the page bottom are all
but
useless. They slow down the loading of the page without adding much
insight.
(I have a simple patch that allows a user to choose whether they want
to see
these graphs.)
o Fix the pie-chart-generating code.
The current pie-chart code is a bit ugly and can plot things incorrectly
under certain circumstances. There must be some nicer graph plotting
packages out there...
Cheers,
Paul.
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