chore(nimbus): add statsd metrics for user interaction counts and review timing (#13412)

Because

- We want more visibility into experimenter activity

This commit

- Adds a count metric for every nimbus ui interaction that generates a
changelog
- Adds a timing metric for how long it takes experiments to be reviewed

Fixes #13409

Author: relud

experimenter/experimenter/nimbus_ui/forms.py

@@ -1,5 +1,7 @@
 from collections import defaultdict
+from datetime import UTC, datetime
 
+import markus
 from django import forms
 from django.contrib.auth.models import User
 from django.forms import inlineformset_factory
@@ -30,6 +32,8 @@
 from experimenter.segments import Segments
 from experimenter.targeting.constants import NimbusTargetingConfig
 
+metrics = markus.get_metrics("experimenter.nimbus_ui_forms")
+
 
 class NimbusChangeLogFormMixin:
     def __init__(self, *args, request: HttpRequest = None, **kwargs):
@@ -44,6 +48,7 @@ def save(self, *args, **kwargs):
         generate_nimbus_changelog(
             experiment, self.request.user, self.get_changelog_message()
         )
+        metrics.incr("changelog_form.save", tags=[f"form:{type(self).__name__}"])
         return experiment
 
 
@@ -1209,6 +1214,7 @@ class Meta:
     def save(self, commit=True):
         self.instance.status = self.status
         self.instance.status_next = self.status_next
+        previous_publish_status = self.instance.publish_status
         self.instance.publish_status = self.publish_status
 
         if self.is_paused is not None:
@@ -1217,6 +1223,20 @@ def save(self, commit=True):
         if self.status == NimbusExperiment.Status.DRAFT:
             self.instance.published_dto = None
 
+        if (
+            previous_publish_status == NimbusExperiment.PublishStatus.REVIEW
+            and self.publish_status != NimbusExperiment.PublishStatus.REVIEW
+        ):
+            last_review_request = self.instance.changes.latest_review_request()
+            if last_review_request is not None:
+                delta = datetime.now(UTC) - last_review_request.changed_on
+                delta_ms = int(delta.total_seconds() * 1000)
+                metrics.timing(
+                    "review_timing",
+                    value=delta_ms,
+                    tags=[f"status:{self.publish_status}"],
+                )
+
         return super().save(commit=commit)
 
 

experimenter/experimenter/nimbus_ui/tests/test_forms.py

@@ -845,6 +845,29 @@ def test_review_to_approve_form(self):
         )
         self.mock_allocate_bucket_range.assert_called_once()
 
+    def test_review_timing_metric(self):
+        data = {
+            "owner": self.user,
+            "name": "Test Experiment",
+            "hypothesis": "test hypothesis",
+            "application": NimbusExperiment.Application.DESKTOP,
+        }
+        form = NimbusExperimentCreateForm(data, request=self.request)
+        self.assertTrue(form.is_valid(), form.errors)
+        experiment = form.save()
+
+        form = DraftToReviewForm(data={}, instance=experiment, request=self.request)
+        self.assertTrue(form.is_valid(), form.errors)
+        experiment = form.save()
+
+        form = ReviewToApproveForm(data={}, instance=experiment, request=self.request)
+        self.assertTrue(form.is_valid(), form.errors)
+
+        with patch("experimenter.nimbus_ui.forms.metrics") as mock_metrics:
+            experiment = form.save()
+
+        mock_metrics.timing.assert_called_once()
+
     def test_live_to_end_enrollment_form(self):
         experiment = NimbusExperimentFactory.create(
             status=NimbusExperiment.Status.LIVE,