[collectd] Announcing “Collection 4” (C4)

Bruno Friedmann bruno at ioda-net.ch
Mon Sep 13 19:17:24 CEST 2010


Wouah, just sound promising, hope to see you in frOsCamp next week.


On 09/13/2010 10:09 AM, Florian Forster wrote:
> Hi everybody,
> 
> I've been working on a new front-end for collectd for some time and
> finally reached a state worth publishing. “Collection 4” (abbreviation
> “C4”) is intended to supersede "Collection 3" eventually, but this
> doesn't mean that I won't accept patches for Collection 3 anymore, of
> course. C4 is far from finished, so expect changes in functionality
> frequently and also in between patch releases.
> 
> The main goal of C4 is performance. Collection 3 had a lot of startup
> overhead, because a lot of Perl-Modules needed to be parsed even when
> only totally unrelated graphs were to be drawn ([0]). C4 uses FastCGI to
> use the same process to handle multiple requests, reducing startup
> costs several magnitudes. Because the available graphs and the list of
> required files for each are kept in memory, most requests can be handled
> without disk access once the process has been initialized. In my
> experience, the browser is the bottleneck now. C4 tries to be friendly
> in this respect by limiting the amount of data sent to the browser to a
> useful size ([1]).
> 
> The second central feature is graph configuration. While many front-ends
> do a great job of displaying arbitrary data nicely, ultimately I want to
> be able to configure the graphs to look exactly the way I want them to
> look. That's why that feature was present in Collection 3 and in
> Collection 2, too. The configuration syntax used in C4 is more flexible
> than the syntax used in Collection 3. It allows create a graph from
> multiple identifiers (think: files) but also allows one identifier to
> appear in multiple graphs. Unfortunately, this is not yet fully
> implemented to users cannot see this feature in all its glory.
> 
> Another important aspect are "data providers": C4 doesn't entirely focus
> on RRD files as the source of its data, but abstracts away the source of
> the data to make it easy to add new "providers" in the future. This
> means, however, that reading ("fetching") the data needs to be separate
> from rendering ("graphing") the data ⇒ no rrdgraph(1) ([2]). Currently
> graphs are rendered using gRaphaël, which currently lacks many graphing
> features supported by the configuration (hence the limitation in the
> previous paragraph). In the near future I hope to see a data provider
> for RRDCacheD (using "rrdc_fetch") and possibly CSV files.
> 
> The HTML-based interface provided by the front-end is very simple and
> leaves a lot of room for improvements. Patches are especially welcome in
> this respect. (Almost?) all the actions are also available in a JSON-
> encoded form. My hope is that better front-end programmers than me use
> this to create nice front-ends based on C4 ([3]), basically using it as a
> back-end ([4]).
> 
> So, without further ado, here's the link to the homepage, wiki page and
> download links:
> 
>   Homepage:  http://octo.it/c4/
>   Wiki:      http://collectd.org/wiki/index.php/Collection_4
>   Download:  http://octo.it/c4/files/collection-4.0.0.tar.bz2
> 
> Needless to say: Feedback is *very* welcome. So are patches :)
> 
> Best regards,
> —octo
> 
> [0] When using the front-end on a smaller scale, you probably don't
>     notice this too much, but when you have 50k+ RRD files and the
>     system is very busy just updating RRD files, you can deliver maybe
>     two graphs per second. I would have expected loading of Perl modules
>     to be a CPU-bound operation once the files containing the modules
>     are in the page cache, but experience tells a different story.
> [1] For example, printing a list of all hosts may result in 100+ kByte
>     sent to the browser on large setups. Having such a list in the menu
>     may be nice when you have 10 hosts. When you have 1000, this will
>     render the interface slow.
> [2] This is only a half-truth: Support for rrdgraph(1)-based images is
>     currently present but not very well maintainable. It *might* be
>     removed in the future or at very least it will be reorganized.
> [3] Lindsay / Visage, I'm looking at you! ;)
> [4] Hey, if it's a front-end and a back-end at the same time, did I just
>     create one of those "middlewares" businesses always get all excited
>     about?! ;)
> 
> 
> 
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> http://mailman.verplant.org/listinfo/collectd


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Bruno Friedmann  bruno at ioda-net.ch

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