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>
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CDEFs
Background
CDEF's in Cacti are a one to one analog to CDEF's in RRDtool. Cacti simply provides an interface to create and manage them. Once the CDEF's are created in Cacti they can be imported and exported globally.
CDEF's are mathematical formulas that either modify the numeric data from one to many data sources or VNAMES that you have in your Graph Template.
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.
CDEF's can get very complex as there are several mathematical functions available in the RRDtool command set.
CDEF Interface
In the image below, you can see all the CDEF's that are included in Cacti by default. There are quite a few of them. Many of the formulas in use are quite simple. If you want to view Tutorials on how to work with CDEF's you should go to the RRDtool Tutorial. There is also documentation at the RRDtool Website.
In this image you can see that you have the ability to Delete or Duplicate a CDEF, but note you will not be able to Delete any CDEF that is associated with a Cacti Graph or Graph Template.
When you Click on the CDEF's name, you will enter into an Edit screen. From there you will see an ordered list of your Stack. It normally will begin with something like the CURRENT_DATA_SOURCE which means that when you Add a Graph Item to either a Graph Template or Graph, you can select a CDEF. The Data Source associated with that Graph Item is the CURRENT_DATA_SOURCE.
After that, you may see a number, followed by a math operator. That is the simplest form of a CDEF. If you have drag & drop enabled, you can re-order the CDEF items using drag & drop. Otherwise you will see arrows that allow you to move the CDEF Items up and down.
When editing a CDEF, the first decision is what Type of Data you want to put on the Stack. Your options are shown in the image below. They include:
| Name | Description |
|---|---|
| Function | A mathematical function that we will describe below |
| Operator | Common mathematical operators including (+, -, *, /, and %) |
| Another CDEF | Another Cacti CDEF. That could be confusing |
| Special Data Source | A value drawn from the Graph, the Data Source, or the poller, described below |
| Custom String | Something like a number, a 'U' or 'Nan' for example |
Special Data Sources
In this next image, you will find a CDEF Item in the process of being added. Note
that when you pick Special Data Source you have a drop-down that appears with
the flavor of Special Data Source. There are many. They include:
| Name | Description |
|---|---|
| Current Graph Item Data Source | The value of the Data Source associated with the Graph Item |
| Current Graph Item Polling Interval | This value is otherwise known as the Step in RRDtool terminology |
| All Data Sources (Do not Include Duplicates) | The total of all Data Sources removing any duplicate DEF's |
| All Data Sources (Include Duplicates) | Add the values from all the Data Sources whether or not they are duplicated |
| All Similar Data Sources (Do not Include Duplicates) | Means all Data Sources with the same RRDtool Data Source name like traffic_in, and traffic_out |
| All Similar Data Sources (Do not Include Duplicates) Polling Interval | The max of the poller intervals returned from all similar Data Sources |
| All Similar Data Sources (Include Duplicates) | Add the values from all similar Data Sources whether or not they are duplicated |
| Current Data Source Item: Minimum Value | The RRDtool minimum value of the Current Data Source |
| Current Data Source Item: Maximum Value | The RRDtool maximum value of the Current Data Source |
| Current Data Source Item: Least Squares Line Function | The RRDtool LSLINT, LSLSLOPE and LSLCORREL set as a least squares line |
| Current Data Source Item: Least Squares Line Y-intercept | The y-intercept of the least squares line for the Current Data Source |
| Current Data Source Item: Least Squares Line Slope | The slope of the least squares line for the Current Data Source |
| Current Data Source Item: Least Squares Line Correlation Coefficient | The correlation coefficient of that least squares line |
| Graph: Lower Limit | The lower Limit of the Graph |
| Graph: Upper Limit | The upper Limit of the Graph |
| Count of All Data Sources (Do not Include Duplicates) | The total count of all Data Sources without Duplication |
| Count of All Data Sources (Include Duplicates) | The total count of all Data Sources including Duplicates |
| Count of All Similar Data Sources (Do not Include Duplicates) | The total count of Data Sources with the same RRDtool Data Source Name, counted once each |
| Count of All Similar Data Sources (Include Duplicates) | The total count of Data Sources with the same RRDtool Data Source Name, including Duplicates |
As you can see there is quite a bit of information that can be pulled from RRDtool for performing Graphical manipulation of Data.
CDEF Functions
This list of CDEF functions is long and it's best to refer directly to the RRDtool Manual for meanings and examples of their use. Cacti supports most of them. If you find one that is not supported, open an Issue on GitHub.
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