Add custom latency buckets from Settings variable

Author: kunalgrover05

README.md

@@ -60,6 +60,17 @@ urlpatterns = [
 ]
 ```
 
+### Configuration
+Prometheus uses Histogram based grouping for monitoring latencies. The default
+buckets are here: https://github.com/prometheus/client_python/blob/master/prometheus_client/core.py
+
+You can define custom buckets for latency, adding more buckets decreases performance but
+increases accuracy: https://prometheus.io/docs/practices/histograms/
+
+```
+PROMETHEUS_LATENCY_BUCKETS = (.1, .2, .5, .6, .8, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.5, 9.0, 12.0, 15.0, 20.0, 30.0, float("inf"))
+```
+
 ### Monitoring your databases
 
 SQLite, MySQL, and PostgreSQL databases can be monitored. Just

django_prometheus/middleware.py

@@ -1,8 +1,27 @@
 from prometheus_client import Counter, Histogram
 
+from django.conf import settings
 from django.utils.deprecation import MiddlewareMixin
 from django_prometheus.utils import PowersOf, Time, TimeSince
 
+DEFAULT_LATENCY_BUCKETS = (
+    0.005,
+    0.01,
+    0.025,
+    0.05,
+    0.075,
+    0.1,
+    0.25,
+    0.5,
+    0.75,
+    1.0,
+    2.5,
+    5.0,
+    7.5,
+    10.0,
+    float("inf"),
+)
+
 
 def _register_metric(cls, name, documentation, labelnames=tuple(), **kwargs):
     return cls(name, documentation, labelnames=labelnames, **kwargs)
@@ -52,24 +71,8 @@ def register(self):
             "django_http_requests_latency_seconds_by_view_method",
             "Histogram of request processing time labelled by view.",
             ["view", "method"],
-            buckets=(
-                0.01,
-                0.025,
-                0.05,
-                0.075,
-                0.1,
-                0.25,
-                0.5,
-                0.75,
-                1.0,
-                2.5,
-                5.0,
-                7.5,
-                10.0,
-                25.0,
-                50.0,
-                75.0,
-                float("inf"),
+            buckets=getattr(
+                settings, "PROMETHEUS_LATENCY_BUCKETS", DEFAULT_LATENCY_BUCKETS
             ),
         )
         self.requests_unknown_latency = _register_metric(