[collectd] Hierarchical storage (for `quota' and `mysql', eg.)

[Niki Waibel]

On 22-Dec-2005 Florian Forster wrote:
> Hi,
> 
> it's pretty much done and working: The `mysql' plugin creates one file
> per command for maximum flexibility. That's 87 files for my version of
> MySQL, but - and that's the reason for doing it this way - this may vary
> for your version of MySQL. Since these files are 113k each they sum up
> to 9.7M, a size database machines should be able to handle ;)

size should be no problem at all. important thing is that it does
not change over time (that's why we're using rrd ;-).

> Since the number of commands is likely a bit bigger the RRD-files are in
> a subdirectory, `mysql', which is a new thing to do for plugins. The
> `quota' plugin will make use of this.. (That's what Niki said at least
> ;)

yes, it will.

> Other than that, the `df' plugin is done and will be in the next
> release. It's using Niki's `utils_mount.[ch]' which works like a charm
>:) All it could need was a better name.. If anyone has an idea let me
> know..

i dont like the naming sceme in collectd. you just cannot figure out
which file is a plugin. on the other hand, creating a dir for all or
dirs for each plugin(s) is maybe also an overhead...

that is the reason why i named the quota stuff
        quota_plugin.[ch]  # plugin interface
        quota_fs.[ch]      # filesystem functions
        quota_mnt.[ch]     # mount functions

> The `configfile' thing is kind of stalled right now since I'm not quite
> sure how to handle config-file _and_ commandline-arguments..

1st some compile-time defaults have to be used
2nd config file options should overwrite the compile time defaults
3rd command line options should overwrite the  config file options

i think that is the most logical way to do it.

> Last and possibly least, I've learned that my assumption about a `jiffy'
> being a fixed time period (10ms) is wrong.

indeed!!!