mirror of
https://github.com/Cacti/documentation.git
synced 2026-10-31 00:57:16 +09:00
Thomas Vincent
57b8088e13
* docs: comprehensive audit, Spine poller overhaul, and technical refactor - Overhaul Spine documentation (Spine.md) with complete end-to-end guide: architecture, prerequisites for modern distros (EL8/9 CRB, Ubuntu 22/24, Debian 11/12, FreeBSD), SUID root permissions, secure spine.conf setup (0640), Web UI configuration (Paths, Poller type, Data Collectors tuning), MySQL max_connections sizing, and troubleshooting. - Fix broken links and anchors (Hardening, SNMP data queries, Hook API references). - Fix broken image reference in Sites.md (add-site.JPG -> add-site.png). - Fix syntax errors in documentation PHP code blocks, including invalid parenthesization, missing SQL execute quotes, and malformed comments in FAQ. - Fix DevOps installation commands: use config.php.dist, correct systemctl service names for MySQL/MariaDB/PHP-FPM, remove nonexistent php-json, add missing composer install, and correct Debian/Ubuntu systemd environment path. - Correct grammatical errors, repeated words, and typos across all markdown documents. - Remove obsolete unreferenced duplicate installation guides. Signed-off-by: Thomas Vincent <thomasvincent@gmail.com> * docs: correct reviewed examples and guidance Signed-off-by: Thomas Vincent <thomasvincent@gmail.com> * docs: correct guidance that disagrees with the Cacti source Verified each claim against include/global_arrays.php, lib/auth.php, lib/functions.php, host_templates.php and the Spine config parser. The notable ones: api_plugin_safe_exec() does not exist on either branch, Spine reads DB_Pass rather than DB_Password, and the CDEF special data source table was missing five entries and renamed four others. Signed-off-by: Thomas Vincent <thomasvincent@gmail.com> * docs: wrap Spine prose and fence the connection sizing formula The formula's bare asterisks rendered as emphasis, dropping the multiplication signs. Signed-off-by: Thomas Vincent <thomasvincent@gmail.com> * chore: refresh copyright year in scripts and issue templates Signed-off-by: Thomas Vincent <thomasvincent@gmail.com> --------- Signed-off-by: Thomas Vincent <thomasvincent@gmail.com>
61 lines
2.4 KiB
Markdown
61 lines
2.4 KiB
Markdown
# VDEFs
|
|
|
|
## Background
|
|
|
|
VDEF's in Cacti are a one to one analog to VDEF's in RRDtool. Cacti
|
|
simply provides an interface to create and manage them. Once the
|
|
VDEF's are created in Cacti they can be imported and exported globally.
|
|
|
|
VDEF's are mathematical formulas that, instead of operating on just
|
|
one Data Point in the RRDfile, operate on the entire Data Set in the time
|
|
range selected. So, VDEF's become a useful tool to replace the
|
|
Nth Percentile and Bandwidth functions in Cacti with the VDEF equivalents.
|
|
|
|
They are referenced in Cacti graphs as VNAMES. However, as mentioned before
|
|
Cacti automatically assigns VNAMES. So, to perform complex operations,
|
|
you will have to experiment to determine the VNAME of your VDEF as you
|
|
build your **Graph Template**. But in their simplest forms, they are
|
|
quite easy to use.
|
|
|
|
The format of the mathematical formulas is called Reverse Polish Notation (RPN).
|
|
RPN was and is an early form of how Engineers entered equations into early
|
|
HP and other Calculators to solve Engineering problems. The reason we still
|
|
use it today is that it follows a simple Stack principle. In other words,
|
|
it's not broken.
|
|
|
|
## VDEF Interface
|
|
|
|
In the image below, you can see all the VDEF's that are included in Cacti by
|
|
default. They are included just to get you thinking about how you would use
|
|
them. You can see straight away the first and the last items are 95th Percentile
|
|
and Bandwidth (or Total) VDEF's. Other examples are pretty self explanatory.
|
|
|
|
You will also note that you can Delete or Duplicate the VDEF's, but as with
|
|
CDEF's you can not Delete a VDEF that is being used in a **Graph**.
|
|
|
|
|
|
|
|
In the image below, you can also see that their interface closely resembles
|
|
the CDEF Interface. Unlike the CDEF's, there is presently only one
|
|
`Special Data Source` and that's the Current Data Source, which makes sense
|
|
when you think about it.
|
|
|
|
|
|
|
|
In the image below, you can see an example of a Single completed VDEF for 95th
|
|
Percentile of the Current Data Source. Pretty straightforward.
|
|
|
|
|
|
|
|
In the next two images, you can see the VDEF Item Types and the complete
|
|
list of VDEF functions. Again, you can reference the
|
|
[RRDtool Documentation](https://oss.oetiker.ch/rrdtool/doc/rrdgraph_rpn.en.html)
|
|
for usage examples for more information.
|
|
|
|
|
|
|
|
|
|
|
|
---
|
|
Copyright (c) 2004-2026 The Cacti Group
|