This tutorial will guide you through all important steps of writing a check with the :pynagiosplugin
class library. Read this to get started.
:pynagiosplugin
has a fine-grained class model with clear separation of concerns. This allows plugin writers to focus on one particular tasks at a time while writing plugins. Nagios/Icinga plugins need to perform three steps: data acquisition
, evaluation
, and presentation
. Each step has an associated class (Resource, Context, Summary) and information between tasks is passed with structured value objects (Metric, Result).
Here is a diagram with the most important classes and their relationships:
+----------+ \
| Resource | |
+----------+ |
_____/ | _____ | Acquisition
v v v |
+---------+ +---------+ +---------+ | | Metric Metric Metric | < +---------+ +---------+ +---------+ | | | | | v v v | +---------+ +---------+ +---------+ | | Context Context Context | | Evaluation +---------+ +---------+ +---------+ | | | | | v v v | +---------+ +---------+ +---------+ | | Result Result Result | < +---------+ +---------+ +---------+ | ___ | ___/ | v v v | Presentation +---------+ | | Summary | | +---------+ /
- Resource
A model of the thing being monitored. It should usually have the same name as the whole plugin. Generates one or more metrics.
Example: system load
- Metric
A single measured data point. A metric consists of a name, a value, a unit, and optional minimum and maximum bounds. Most metrics are scalar (the value can be represented as single number).
Example: load1=0.75
- Context
Additional information to evaluate a metric. A context has usually a warning and critical range which allows to determine if a given metric is OK or not. Contexts also include information on how to present a metric in a human-readable way.
Example: warning=0.5, critical=1.0
- Result
Product of a metric and a context. A result consists of a state ("ok", "warning", "critical", "unknown"), some explanatory text, and references to the objects that it was generated from.
Example: WARNING - load1 is 0.75
- Summary
Condenses all results in a single status line. The status line is the plugin's most important output: it appears in mails, text messages, pager alerts etc.
Example: LOAD WARNING - load1 is 0.75 (greater than 0.5)
The following tutorials which will guide you through the most important features of nagiosplugin
.
Hint
Study the source code in the nagiosplugin/examples
directory for complete examples.
check_world check_load check_users