.. currentmodule:: nagiosplugin
In the first tutorial, we will develop check_world. This check will determine if the world exists. The algorithm is simple: if the world would not exist, the check would not execute.
This minimalistic check consists of a :py:class:`Resource` World which models the part of the world that is interesting for the purposes of our check. Resource classes must define a :py:meth:`Resource.probe` method which returns a list of metrics. We just return a single :py:class:`Metric` object that states that the world exists.
.. literalinclude:: /../nagiosplugin/examples/check_world.py
We don't have a context to evaluate the returned metric yet, so we resort to the built-in "null" context. The "null" context does nothing with its associated metrics.
We now create a :py:class:`Check` object that is fed only with the resource object. We could put context and summary objects into the :py:meth:`Check()` constructor as well. This will be demonstrated in the next tutorial. There is also no command line processing nor timeout handling nor output control. We call the :py:meth:`Check.main` method to evaluate resources, construct text output and exit with the appropriate status code.
Running the plugin creates very simple output:
$ check_world.py
WORLD OKThe plugin's exit status is 0, signalling success to the calling process.