[enh] settings.yml: implement general.enable_metrics

* allow not to record metrics (response time, etc...)
* this commit doesn't change the UI. If the metrics are disabled
  /stats and /stats/errors will return empty response.
  in /preferences, the columns response time and reliability will be empty.

searx/metrics/__init__.py

@@ -9,7 +9,7 @@ from timeit import default_timer
 from operator import itemgetter
 
 from searx.engines import engines
-from .models import HistogramStorage, CounterStorage
+from .models import HistogramStorage, CounterStorage, VoidHistogram, VoidCounterStorage
 from .error_recorder import count_error, count_exception, errors_per_engines
 
 __all__ = [
@@ -69,14 +69,18 @@ def counter(*args):
     return counter_storage.get(*args)
 
 
-def initialize(engine_names=None):
+def initialize(engine_names=None, enabled=True):
     """
     Initialize metrics
     """
     global counter_storage, histogram_storage  # pylint: disable=global-statement
 
-    counter_storage = CounterStorage()
-    histogram_storage = HistogramStorage()
+    if enabled:
+        counter_storage = CounterStorage()
+        histogram_storage = HistogramStorage()
+    else:
+        counter_storage = VoidCounterStorage()
+        histogram_storage = HistogramStorage(histogram_class=VoidHistogram)
 
     # max_timeout = max of all the engine.timeout
     max_timeout = 2

searx/metrics/error_recorder.py

@@ -9,7 +9,7 @@ from searx.exceptions import (
     SearxEngineAPIException,
     SearxEngineAccessDeniedException,
 )
-from searx import searx_parent_dir
+from searx import searx_parent_dir, settings
 from searx.engines import engines
 
 
@@ -165,6 +165,8 @@ def get_error_context(framerecords, exception_classname, log_message, log_parame
 
 
 def count_exception(engine_name: str, exc: Exception, secondary: bool = False) -> None:
+    if not settings['general']['enable_metrics']:
+        return
     framerecords = inspect.trace()
     try:
         exception_classname = get_exception_classname(exc)
@@ -178,6 +180,8 @@ def count_exception(engine_name: str, exc: Exception, secondary: bool = False) -
 def count_error(
     engine_name: str, log_message: str, log_parameters: typing.Optional[typing.Tuple] = None, secondary: bool = False
 ) -> None:
+    if not settings['general']['enable_metrics']:
+        return
     framerecords = list(reversed(inspect.stack()[1:]))
     try:
         error_context = get_error_context(framerecords, None, log_message, log_parameters or (), secondary)

searx/metrics/models.py

@@ -102,16 +102,17 @@ class Histogram:
 
 class HistogramStorage:
 
-    __slots__ = 'measures'
+    __slots__ = 'measures', 'histogram_class'
 
-    def __init__(self):
+    def __init__(self, histogram_class=Histogram):
         self.clear()
+        self.histogram_class = histogram_class
 
     def clear(self):
         self.measures = {}
 
     def configure(self, width, size, *args):
-        measure = Histogram(width, size)
+        measure = self.histogram_class(width, size)
         self.measures[args] = measure
         return measure
 
@@ -154,3 +155,13 @@ class CounterStorage:
         logger.debug("Counters:")
         for k in ks:
             logger.debug("- %-60s %s", '|'.join(k), self.counters[k])
+
+
+class VoidHistogram(Histogram):
+    def observe(self, value):
+        pass
+
+
+class VoidCounterStorage(CounterStorage):
+    def add(self, value, *args):
+        pass