python loaders cleanup (#5602)

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##### Summary
python loaders module cleanup
 - move `load_module` to `python.d.plugin`
 - use `load_config` in unbound module instead of YamlOrderedLoad class
 - remove all classes from `loaders.py` - no longer used

##### Component Name
[`collectors/python.d.plugin/python_modules/bases/loaders`](https://github.com/netdata/netdata/blob/master/collectors/python.d.plugin/python_modules/bases/loaders.py)
##### Additional Information

3 files changed, 28 insertions, 67 deletions

diff --git a/collectors/python.d.plugin/python.d.plugin.in b/collectors/python.d.plugin/python.d.plugin.in
index 8ce621e0bd..cca7346a1e 100644
--- a/collectors/python.d.plugin/python.d.plugin.in
+++ b/collectors/python.d.plugin/python.d.plugin.in
@@ -18,6 +18,15 @@ import re
 import sys
 import time
 import threading
+import types
+
+PY_VERSION = sys.version_info[:2]
+
+if PY_VERSION > (3, 1):
+    from importlib.machinery import SourceFileLoader
+else:
+    from imp import load_source as SourceFileLoader
+
 
 ENV_NETDATA_USER_CONFIG_DIR = 'NETDATA_USER_CONFIG_DIR'
 ENV_NETDATA_STOCK_CONFIG_DIR = 'NETDATA_STOCK_CONFIG_DIR'
@@ -73,7 +82,6 @@ sys.path.append(DIRS.pythond_packages)
 from bases.collection import safe_print
 from bases.loggers import PythonDLogger
 from bases.loaders import load_config
-from bases.loaders import load_module as _load_module
 
 try:
     from collections import OrderedDict
@@ -138,7 +146,10 @@ class HeartBeat(threading.Thread):
 
 def load_module(name):
     abs_path = os.path.join(DIRS.modules, '{0}{1}'.format(name, MODULE_SUFFIX))
-    return _load_module(name, abs_path)
+    module = SourceFileLoader(name, abs_path)
+    if isinstance(module, types.ModuleType):
+        return module
+    return module.load_module()
 
 
 def multi_path_find(name, paths):
@@ -504,6 +515,8 @@ class Plugin:
         self.task_queue.join()
         self.dequeue_results()
         self.result_queue.join()
+        self.task_queue.close()
+        self.result_queue.close()
         self.log.info('stopping checker process')
         worker.join()
 
@@ -588,7 +601,8 @@ class Plugin:
         while True:
             self.runs += 1
 
-            if threading.active_count() <= 3 and not self.auto_detection_jobs:
+            # threads: main + heartbeat
+            if threading.active_count() <= 2 and not self.auto_detection_jobs:
                 return
 
             time.sleep(1)
@@ -678,7 +692,7 @@ def main():
     if cmd.trace:
         logger.log_traceback = True
 
-    logger.info('using python v{0}'.format(sys.version_info[:2][0]))
+    logger.info('using python v{0}'.format(PY_VERSION[0]))
 
     unknown_modules = set(cmd.modules_to_run) - set(AVAILABLE_MODULES)
     if unknown_modules:
diff --git a/collectors/python.d.plugin/python_modules/bases/loaders.py b/collectors/python.d.plugin/python_modules/bases/loaders.py
index 921a09f917..d8b2ec8159 100644
--- a/collectors/python.d.plugin/python_modules/bases/loaders.py
+++ b/collectors/python.d.plugin/python_modules/bases/loaders.py
@@ -3,7 +3,6 @@
 # Author: Ilya Mashchenko (l2isbad)
 # SPDX-License-Identifier: GPL-3.0-or-later
 
-import types
 
 from sys import version_info
 
@@ -18,78 +17,22 @@ except ImportError:
     from yaml import SafeLoader as YamlSafeLoader
 
 
-if PY_VERSION > (3, 1):
-    from importlib.machinery import SourceFileLoader
-    DEFAULT_MAPPING_TAG = 'tag:yaml.org,2002:map'
-else:
-    from imp import load_source as SourceFileLoader
-    DEFAULT_MAPPING_TAG = u'tag:yaml.org,2002:map'
-
 try:
     from collections import OrderedDict
 except ImportError:
     from third_party.ordereddict import OrderedDict
 
 
-def dict_constructor(loader, node):
-    return OrderedDict(loader.construct_pairs(node))
+DEFAULT_MAPPING_TAG = 'tag:yaml.org,2002:map' if PY_VERSION > (3, 1) else u'tag:yaml.org,2002:map'
 
 
-def safe_load(stream):
-    loader = YamlSafeLoader(stream)
-    try:
-        return loader.get_single_data()
-    finally:
-        loader.dispose()
+def dict_constructor(loader, node):
+    return OrderedDict(loader.construct_pairs(node))
 
 
 YamlSafeLoader.add_constructor(DEFAULT_MAPPING_TAG, dict_constructor)
 
 
-class YamlOrderedLoader:
-    @staticmethod
-    def load_config_from_file(file_name):
-        opened, loaded = False, False
-        try:
-            stream = open(file_name, 'r')
-            opened = True
-            loader = YamlSafeLoader(stream)
-            loaded = True
-            parsed = loader.get_single_data() or dict()
-        except Exception as error:
-            return dict(), error
-        else:
-            return parsed, None
-        finally:
-            if opened:
-                stream.close()
-            if loaded:
-                loader.dispose()
-
-
-class SourceLoader:
-    @staticmethod
-    def load_module_from_file(name, path):
-        try:
-            loaded = SourceFileLoader(name, path)
-            if isinstance(loaded, types.ModuleType):
-                return loaded, None
-            return loaded.load_module(), None
-        except Exception as error:
-            return None, error
-
-
-class ModuleAndConfigLoader(YamlOrderedLoader, SourceLoader):
-    pass
-
-
-def load_module(name, path):
-    module = SourceFileLoader(name, path)
-    if isinstance(module, types.ModuleType):
-        return module
-    return module.load_module()
-
-
 def load_yaml(stream):
     loader = YamlSafeLoader(stream)
     try:
diff --git a/collectors/python.d.plugin/unbound/unbound.chart.py b/collectors/python.d.plugin/unbound/unbound.chart.py
index adb58d4176..dade2b2041 100644
--- a/collectors/python.d.plugin/unbound/unbound.chart.py
+++ b/collectors/python.d.plugin/unbound/unbound.chart.py
@@ -9,7 +9,7 @@ import sys
 from copy import deepcopy
 
 from bases.FrameworkServices.SocketService import SocketService
-from bases.loaders import YamlOrderedLoader
+from bases.loaders import load_config
 
 PRECISION = 1000
 
@@ -169,7 +169,7 @@ def _get_perthread_info(thread):
     for key, value in PER_THREAD_STAT_MAP.items():
         statmap[key.format(shortname=sname)] = (value[0].format(shortname=sname), value[1])
 
-    return (charts, order, statmap)
+    return charts, order, statmap
 
 
 class Service(SocketService):
@@ -205,7 +205,11 @@ class Service(SocketService):
     def _auto_config(self):
         if self.ubconf and os.access(self.ubconf, os.R_OK):
             self.debug('Unbound config: {0}'.format(self.ubconf))
-            conf = YamlOrderedLoader.load_config_from_file(self.ubconf)[0]
+            conf = dict()
+            try:
+                conf = load_config(self.ubconf)
+            except Exception as error:
+                self.error("error on loading '{0}' : {1}".format(self.ubconf, error))
             if self.ext is None:
                 if 'extended-statistics' in conf['server']:
                     self.ext = conf['server']['extended-statistics']