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* 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>
103 lines
5.7 KiB
Markdown
103 lines
5.7 KiB
Markdown
# CDEFs
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## Background
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CDEF's in Cacti are a one to one analog to CDEF's in RRDtool. Cacti
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simply provides an interface to create and manage them. Once the
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CDEF's are created in Cacti they can be imported and exported globally.
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CDEF's are mathematical formulas that either modify the numeric data from
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one to many data sources or VNAMES that you have in your **Graph Template**.
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The format of the mathematical formulas is called Reverse Polish Notation (RPN).
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RPN was and is an early form of how Engineers entered equations into early
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HP and other Calculators to solve Engineering problems. The reason we still
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use it today is that it follows a simple Stack principle. In other words,
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it's not broken.
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CDEF's can get very complex as there are several mathematical functions
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available in the RRDtool command set.
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## CDEF Interface
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In the image below, you can see all the CDEF's that are included in Cacti by
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default. There are quite a few of them. Many of the formulas in use are quite
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simple. If you want to view Tutorials on how to work with CDEF's you should
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go to the [RRDtool Tutorial](https://oss.oetiker.ch/rrdtool/tut/cdeftutorial.en.html).
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There is also documentation at the [RRDtool Website](https://oss.oetiker.ch/rrdtool/doc/rrdgraph_data.en.html#CDEF).
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In this image you can see that you have the ability to Delete or Duplicate a CDEF,
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but note you will not be able to Delete any CDEF that is associated with a Cacti
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**Graph** or **Graph Template**.
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When you Click on the CDEF's name, you will enter into an Edit screen. From there
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you will see an ordered list of your Stack. It normally will begin with something
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like the CURRENT_DATA_SOURCE which means that when you Add a **Graph Item** to
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either a **Graph Template** or **Graph**, you can select a CDEF. The
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**Data Source** associated with that **Graph Item** is the CURRENT_DATA_SOURCE.
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After that, you may see a number, followed by a math operator. That is the
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simplest form of a CDEF. If you have drag & drop enabled, you can re-order the
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CDEF items using drag & drop. Otherwise you will see arrows that allow you
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to move the CDEF Items up and down.
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When editing a CDEF, the first decision is what Type of Data you want to put on
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the Stack. Your options are shown in the image below. They include:
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Name | Description
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--- | ---
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Function | A mathematical function that we will describe below
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Operator | Common mathematical operators including (+, -, *, /, and %)
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Another CDEF | Another Cacti CDEF. That could be confusing
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Special Data Source | A value drawn from the Graph, the Data Source, or the poller, described below
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Custom String | Something like a number, a 'U' or 'Nan' for example
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## Special Data Sources
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In this next image, you will find a CDEF Item in the process of being added. Note
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that when you pick `Special Data Source` you have a drop-down that appears with
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the flavor of `Special Data Source`. There are many. They include:
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Name | Description
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--- | ---
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Current Graph Item Data Source | The value of the Data Source associated with the Graph Item
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Current Graph Item Polling Interval | This value is otherwise known as the Step in RRDtool terminology
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All Data Sources (Do not Include Duplicates) | The total of all Data Sources removing any duplicate DEF's
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All Data Sources (Include Duplicates) | Add the values from all the Data Sources whether or not they are duplicated
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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
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All Similar Data Sources (Do not Include Duplicates) Polling Interval | The max of the poller intervals returned from all similar Data Sources
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All Similar Data Sources (Include Duplicates) | Add the values from all similar Data Sources whether or not they are duplicated
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Current Data Source Item: Minimum Value | The RRDtool minimum value of the Current Data Source
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Current Data Source Item: Maximum Value | The RRDtool maximum value of the Current Data Source
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Current Data Source Item: Least Squares Line Function | The RRDtool LSLINT, LSLSLOPE and LSLCORREL set as a least squares line
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Current Data Source Item: Least Squares Line Y-intercept | The y-intercept of the least squares line for the Current Data Source
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Current Data Source Item: Least Squares Line Slope | The slope of the least squares line for the Current Data Source
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Current Data Source Item: Least Squares Line Correlation Coefficient | The correlation coefficient of that least squares line
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Graph: Lower Limit | The lower Limit of the Graph
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Graph: Upper Limit | The upper Limit of the Graph
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Count of All Data Sources (Do not Include Duplicates) | The total count of all Data Sources without Duplication
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Count of All Data Sources (Include Duplicates) | The total count of all Data Sources including Duplicates
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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
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Count of All Similar Data Sources (Include Duplicates) | The total count of Data Sources with the same RRDtool Data Source Name, including Duplicates
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As you can see there is quite a bit of information that can be pulled from
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RRDtool for performing Graphical manipulation of Data.
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## CDEF Functions
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This list of CDEF functions is long and it's best to refer directly to the
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[RRDtool Manual](https://oss.oetiker.ch/rrdtool/doc/rrdgraph_rpn.en.html) for meanings
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and examples of their use. Cacti supports most of them. If you find one that
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is not supported, open an [Issue on GitHub](https://github.com/Cacti/cacti/issues).
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---
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Copyright (c) 2004-2026 The Cacti Group
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