Allow fully qualified collector modules (#45)

* Allow fully qualified collector modules

To make development of collectors more indipendent from p3exporter developments we now allow fully qualified (dotted notation) module names.
Naming convention of collector class stay in place.

* Update CHANGELOG.md

add new feature to changelog

Author: cmeissner

CHANGELOG.md

@@ -6,6 +6,7 @@ This project adheres to [Semantic Versioning](http://semver.org/) and [Keep a Ch
 ## Unreleased
 
 ### New
+* Allow to load external collectors with fully qualified dotted notation
 
 ### Changes
 * Switch sphinx from recommonmark to myst_parser

p3.yml

@@ -1,6 +1,6 @@
 exporter_name: "Python prammable Prometheus exporter"
 collectors:
-  - example
+  - p3exporter.collector.example
   - loadavg
   - netdev
 collector_opts:

p3exporter/collector/__init__.py

@@ -62,7 +62,10 @@ def collector_name_from_class(self):
 class Collector(object):
     """Base class to load collectors.
 
-    All collectors have to be placed inside the directory `collector`. You have to follow the naming convention:
+    Collectors needs to be placed either in the directory `collector` within this module (local) or in a separate module.
+    Collectors in separate modules needs to be addressed in dotted notation.
+
+    Collectors have to follow the following naming convention:
 
     1. Place the collector code in a <name>.py file (e.g. `my.py`)
     2. Within the file <name>.py` a class <Name>Collector (e.g. `MyController`) needs to be defined.
@@ -71,10 +74,11 @@ class Collector(object):
 
     def __init__(self, config: CollectorConfig):
         """Instantiate an CollectorBase object."""
-        for c in config.collectors:
+        _collectors = [c if "." in c else "p3exporter.collector.{}".format(c) for c in config.collectors]
+        for c in _collectors:
             try:
-                collector_module = import_module("p3exporter.collector.{}".format(c), package=None)
-                collector_class = getattr(collector_module, "{0}Collector".format(inflection.camelize(c)))
+                collector_module = import_module(c, package=None)
+                collector_class = getattr(collector_module, "{0}Collector".format(inflection.camelize(c.split('.')[-1])))
                 collector = collector_class(config)
                 REGISTRY.register(collector)
                 logging.info("Collector '{0}' was loaded and registred successfully".format(c))