On Tue, Dec 29, 2009 at 9:23 PM, Sebastian Harl <[email protected]> wrote:
> Hi Amit, > > On Tue, Dec 29, 2009 at 07:24:46PM +0530, Amit Gupta wrote: > > On Tue, Dec 29, 2009 at 3:31 PM, Amit Gupta <[email protected]> > wrote: > > > On Mon, Dec 21, 2009 at 11:59 PM, Florian Forster <[email protected] > >wrote: > > > Just a clarification, "Instance" here will be type_instance(s) and thus > can > > > be anything (not just xpath), right? > > > > I guess I understood why "Instance" has to be a xpath expression if > "table" > > is true. Instance xpath would return list of values which will be used as > > type_instances for multiple type values returned by evaluating xpaths in > > "Values". Is my understanding correct?. > > Yep, that's right. > > If "Table" is false, a simple string would be sufficient as well, but > changing the semantics of "Instance" depending on "Table" would be > confusing -- also, people might still want to fetch the instance from > the XML file. > > Other plugins (e.g., postgresql) handle that by introducing an option > called "InstancePrefix" which expects a string as argument. That string > is prepended to the type_instance. > > If "Table" is false, "Instance" would be optional, thus making it > possible to specify a constant string as type_instance using "Instance- > Prefix". > Thanks for the detailed explanation. I was thinking about the implementation of the suggested configuration and it seems that the implementation can be simpler if we consider the following approach: The evaluation of the <base_xpath> (i.e argument to the XPATH element) will return either of the following: a.) Single result: This can be assumed as "Table" false case. The relative xpath expression(s) in "Values" is/are always expected to return one text node/attribute result. b.) Multiple results : This can be assumed as "Table" true case. "Instance" xpath expression will be evaluated and result(s) will be stored in a list. Multiple results will be iterated and the relative xpath(s) in "Values" will be evaluated relative to each of the result (node) [the result(s) of the relative xpath(s) can be dispatched to the rrd file at the same time]. The relative xpath expression(s) in "Values" is/are always expected to return one text node/attribute result. Do note that "Table" won't be required since single/multiple result(s) of the <base_xpath> evaluation can be used for the same as described above. Does this make sense?. Let me know if something is unclear. Regards Amit > > Cheers, > Sebastian > > -- > Sebastian "tokkee" Harl +++ GnuPG-ID: 0x8501C7FC +++ http://tokkee.org/ > > Those who would give up Essential Liberty to purchase a little Temporary > Safety, deserve neither Liberty nor Safety. -- Benjamin Franklin > > > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1.4.9 (GNU/Linux) > > iEYEARECAAYFAks6JgcACgkQEFEKc4UBx/zbtQCfWIIVzQr9nhm1sHZPpedUkmRV > W7AAmwfaoj4/EhrGveBDh7yCbbJ7EUVv > =NM8M > -----END PGP SIGNATURE----- > >
_______________________________________________ collectd mailing list [email protected] http://mailman.verplant.org/listinfo/collectd
