chore(dynamic-sampling): add more detailed logs to sample rate calculations (#97563)

Author: shellmayr

src/sentry/dynamic_sampling/tasks/boost_low_volume_projects.py

@@ -250,13 +250,19 @@ def boost_low_volume_projects_of_org(
     Task to adjust the sample rates of the projects of a single organization specified by an
     organization ID. Transaction counts and rates have to be provided.
     """
-    logger.info(
-        "boost_low_volume_projects_of_org",
-        extra={"traceparent": sentry_sdk.get_traceparent(), "baggage": sentry_sdk.get_baggage()},
-    )
+
     rebalanced_projects = calculate_sample_rates_of_projects(
         org_id, projects_with_tx_count_and_rates
     )
+
+    logger.info(
+        "boost_low_volume_projects_of_org",
+        extra={
+            "traceparent": sentry_sdk.get_traceparent(),
+            "baggage": sentry_sdk.get_baggage(),
+            "org_id": org_id,
+        },
+    )
     if rebalanced_projects is not None:
         store_rebalanced_projects(org_id, rebalanced_projects)
 
@@ -435,10 +441,27 @@ def calculate_sample_rates_of_projects(
 
     # If we have the sliding window org sample rate, we use that or fall back to the blended sample rate in case of
     # issues.
+
+    default_sample_rate = quotas.backend.get_blended_sample_rate(organization_id=org_id)
+    should_log_project_config = features.has("organizations:log-project-config", organization)
+
     sample_rate, success = get_org_sample_rate(
         org_id=org_id,
-        default_sample_rate=quotas.backend.get_blended_sample_rate(organization_id=org_id),
+        default_sample_rate=default_sample_rate,
     )
+
+    if should_log_project_config:
+        logger.info(
+            "log-project-config: calculate_sample_rates_of_projects for org %s",
+            org_id,
+            extra={
+                "org": org_id,
+                "target_sample_rate": sample_rate,
+                "success": success,
+                "default_sample_rate": default_sample_rate,
+            },
+        )
+
     if success:
         sample_function(
             function=log_sample_rate_source,
@@ -470,6 +493,14 @@ def calculate_sample_rates_of_projects(
     projects_with_counts = {
         project_id: count_per_root for project_id, count_per_root, _, _ in projects_with_tx_count
     }
+
+    if should_log_project_config:
+        logger.info(
+            "log-project-config: calculate_sample_rates_of_projects for org %s",
+            org_id,
+            extra={"projects_with_counts": projects_with_counts, "sample_rate": sample_rate},
+        )
+
     # The rebalancing will not work (or would make sense) when we have only projects with zero-counts.
     if not any(projects_with_counts.values()):
         return None
@@ -502,6 +533,26 @@ def calculate_sample_rates_of_projects(
     rebalanced_projects: list[RebalancedItem] | None = guarded_run(
         model, ProjectsRebalancingInput(classes=projects, sample_rate=sample_rate)
     )
+    if should_log_project_config:
+        logger.info(
+            "log-project-config: rebalanced_projects for org %s",
+            org_id,
+            extra={
+                "rebalanced_projects": (
+                    [
+                        {
+                            "id": project.id,
+                            "count": project.count,
+                            "new_sample_rate": project.new_sample_rate,
+                        }
+                        for project in rebalanced_projects
+                    ]
+                    if rebalanced_projects
+                    else None
+                ),
+                "sample_rate": sample_rate,
+            },
+        )
 
     return rebalanced_projects
 

src/sentry/dynamic_sampling/tasks/helpers/sample_rate.py

@@ -8,6 +8,10 @@
 
 __all__ = ["get_org_sample_rate"]
 
+import logging
+
+logger = logging.getLogger("sentry.dynamic_sampling")
+
 
 def get_org_sample_rate(
     org_id: int, default_sample_rate: float | None
@@ -28,14 +32,35 @@ def get_org_sample_rate(
     has_dynamic_sampling_custom = features.has("organizations:dynamic-sampling-custom", org)
     if has_dynamic_sampling_custom:
         sample_rate = org.get_option("sentry:target_sample_rate") if org else None
+        if features.has("organizations:log-project-config", org):
+            logger.info(
+                "log-project-config: org.get_option: %s",
+                sample_rate,
+                extra={
+                    "org": org.id if org else None,
+                    "target_sample_rate": sample_rate,
+                    "default_sample_rate": default_sample_rate,
+                },
+            )
         if sample_rate is not None:
             return float(sample_rate), True
         if default_sample_rate is not None:
             return default_sample_rate, False
         return TARGET_SAMPLE_RATE_DEFAULT, False
 
     # fallback to sliding window calculation
-    return _get_sliding_window_org_sample_rate(org_id, default_sample_rate)
+    sample_rate, is_custom = _get_sliding_window_org_sample_rate(org_id, default_sample_rate)
+    if features.has("organizations:log-project-config", org):
+        logger.info(
+            "log-project-config: _get_sliding_window_org_sample_rate for org %s",
+            org_id,
+            extra={
+                "sample_rate": sample_rate,
+                "is_custom": is_custom,
+                "default_sample_rate": default_sample_rate,
+            },
+        )
+    return sample_rate, is_custom
 
 
 def _get_sliding_window_org_sample_rate(