ref(metrics-extraction): Reduce cold cache peak w/ rolling cache (#68727

)

### Summary
This splits up the cache into 6 chunks and spreads out the ttl so at any
one extraction only part of the cache is cold.

src/sentry/relay/config/metric_extraction.py

@@ -35,6 +35,7 @@
 from sentry.search.events.types import ParamsType, QueryBuilderConfig
 from sentry.snuba.dataset import Dataset
 from sentry.snuba.metrics.extraction import (
+    WIDGET_QUERY_CACHE_MAX_CHUNKS,
     MetricSpec,
     MetricSpecType,
     OnDemandMetricSpec,
@@ -204,20 +205,39 @@ def _get_alert_metric_specs(
     return specs
 
 
-def _bulk_cache_query_key(project: Project) -> str:
-    return f"on-demand.bulk-query-cache.{project.organization.id}"
+def _bulk_cache_query_key(project: Project, chunk: int) -> str:
+    return f"on-demand.bulk-query-cache.{chunk}.{project.organization.id}"
 
 
-def _get_bulk_cached_query(project: Project) -> dict[str, Any]:
-    query_bulk_cache_key = _bulk_cache_query_key(project)
-    cache_result = cache.get(query_bulk_cache_key, None)
-    sentry_sdk.set_tag("on_demand_metrics.query_cache", cache_result is None)
-    return cache_result
+def _get_bulk_cached_query(project: Project) -> tuple[dict[int, dict[str, bool]], list[int]]:
+    cache_result = {}
+    cold_cache_chunks = []
+    for i in range(WIDGET_QUERY_CACHE_MAX_CHUNKS):
+        query_bulk_cache_key = _bulk_cache_query_key(project, i)
+        chunk_result = cache.get(query_bulk_cache_key, None)
+        if chunk_result is None:
+            cold_cache_chunks.append(i)
+        sentry_sdk.set_tag(f"on_demand_metrics.query_cache.{i}", chunk_result is None)
+        cache_result[i] = chunk_result or {}
+    sentry_sdk.set_extra("cold_cache_chunks", cold_cache_chunks)
+    metrics.incr("on_demand_metrics.query_cache_cold_keys", amount=len(cold_cache_chunks))
+    return cache_result, cold_cache_chunks
 
 
-def _set_bulk_cached_query(project: Project, query_cache: dict[str, Any]) -> None:
-    query_bulk_cache_key = _bulk_cache_query_key(project)
-    cache.set(query_bulk_cache_key, query_cache, timeout=5400)
+def _set_bulk_cached_query_chunk(
+    project: Project, chunk_cache: dict[str, bool], chunk: int
+) -> None:
+    query_bulk_cache_key = _bulk_cache_query_key(project, chunk)
+    cache.set(
+        query_bulk_cache_key, chunk_cache, timeout=900 + (137 * chunk)
+    )  # Add prime number jitter per cache. All cache turns over between 15-25 mins
+
+
+def _set_bulk_cached_query(
+    project: Project, query_cache: dict[int, dict[str, bool]], cold_cache_chunks: list[int]
+) -> None:
+    for i in cold_cache_chunks:
+        _set_bulk_cached_query_chunk(project, query_cache[i], i)
 
 
 @metrics.wraps("on_demand_metrics._get_widget_metric_specs")
@@ -247,9 +267,7 @@ def _get_widget_metric_specs(
         "on_demand_metrics.widgets_to_process", amount=len(widget_queries), sample_rate=1.0
     )
 
-    organization_bulk_query_cache = _get_bulk_cached_query(project)
-    save_organization_bulk_cache = not bool(organization_bulk_query_cache)
-    organization_bulk_query_cache = {}
+    organization_bulk_query_cache, cold_bulk_cache_chunks = _get_bulk_cached_query(project)
 
     ignored_widget_ids: dict[int, bool] = {}
     specs_for_widget: dict[int, list[HashedMetricSpec]] = defaultdict(list)
@@ -309,8 +327,7 @@ def _get_widget_metric_specs(
     _update_state_with_spec_limit(trimmed_specs, widget_query_for_spec_hash)
     metrics.incr("on_demand_metrics.widget_query_specs", amount=len(specs))
     if in_random_rollout("on_demand_metrics.cache_should_use_on_demand"):
-        if save_organization_bulk_cache:
-            _set_bulk_cached_query(project, organization_bulk_query_cache)
+        _set_bulk_cached_query(project, organization_bulk_query_cache, cold_bulk_cache_chunks)
     return specs
 
 
@@ -439,7 +456,7 @@ def convert_widget_query_to_metric(
     project: Project,
     widget_query: DashboardWidgetQuery,
     prefilling: bool,
-    organization_bulk_query_cache: dict[str, Any] | None = None,
+    organization_bulk_query_cache: dict[int, dict[str, bool]] | None = None,
 ) -> list[HashedMetricSpec]:
     """
     Converts a passed metrics widget query to one or more MetricSpecs.
@@ -467,7 +484,7 @@ def _generate_metric_specs(
     project: Project,
     prefilling: bool,
     groupbys: Sequence[str] | None = None,
-    organization_bulk_query_cache: dict[str, Any] | None = None,
+    organization_bulk_query_cache: dict[int, dict[str, bool]] | None = None,
 ) -> list[HashedMetricSpec]:
     metrics_specs = []
     metrics.incr("on_demand_metrics.before_widget_spec_generation")
@@ -739,7 +756,7 @@ def _convert_aggregate_and_query_to_metrics(
     prefilling: bool,
     spec_type: MetricSpecType = MetricSpecType.SIMPLE_QUERY,
     groupbys: Sequence[str] | None = None,
-    organization_bulk_query_cache: dict[str, Any] | None = None,
+    organization_bulk_query_cache: dict[int, dict[str, bool]] | None = None,
 ) -> Sequence[HashedMetricSpec] | None:
     """
     Converts an aggregate and a query to a metric spec with its hash value.

src/sentry/snuba/metrics/extraction.py

@@ -59,6 +59,9 @@
     "user_misery": SPEC_VERSION_TWO_FLAG,
 }
 
+# Splits the bulk cache for on-demand resolution into N chunks
+WIDGET_QUERY_CACHE_MAX_CHUNKS = 6
+
 
 # This helps us control the different spec versions
 # in order to migrate customers from invalid specs
@@ -670,18 +673,22 @@ def should_use_on_demand_metrics(
     query: str | None,
     groupbys: Sequence[str] | None = None,
     prefilling: bool = False,
-    organization_bulk_query_cache: dict[str, Any] | None = None,
+    organization_bulk_query_cache: dict[int, dict[str, bool]] | None = None,
 ) -> bool:
     if in_random_rollout("on_demand_metrics.cache_should_use_on_demand"):
         if organization_bulk_query_cache is None:
             organization_bulk_query_cache = {}
 
         dataset_str = dataset.value if isinstance(dataset, Enum) else str(dataset or "")
         groupbys_str = ",".join(sorted(groupbys)) if groupbys else ""
-        local_cache_key = md5_text(
+        local_cache_md5 = md5_text(
             f"{dataset_str}-{aggregate}-{query or ''}-{groupbys_str}-prefilling={prefilling}"
-        ).hexdigest()
-        cached_result = organization_bulk_query_cache.get(local_cache_key, None)
+        )
+        local_cache_digest_chunk = local_cache_md5.digest()[0] % WIDGET_QUERY_CACHE_MAX_CHUNKS
+        local_cache_key = local_cache_md5.hexdigest()
+        cached_result = organization_bulk_query_cache.get(local_cache_digest_chunk, {}).get(
+            local_cache_key, None
+        )
         if cached_result:
             metrics.incr("on_demand_metrics.should_use_on_demand_metrics.cache_hit")
             return cached_result
@@ -700,7 +707,7 @@ def should_use_on_demand_metrics(
                 prefilling=prefilling,
             )
             metrics.incr("on_demand_metrics.should_use_on_demand_metrics.cache_miss")
-            organization_bulk_query_cache[local_cache_key] = result
+            organization_bulk_query_cache[local_cache_digest_chunk][local_cache_key] = result
             return result
 
     return _should_use_on_demand_metrics(

tests/sentry/relay/config/test_metric_extraction.py

@@ -12,7 +12,7 @@
 from sentry.models.transaction_threshold import ProjectTransactionThreshold, TransactionMetric
 from sentry.relay.config.experimental import TimeChecker
 from sentry.relay.config.metric_extraction import (
-    _set_bulk_cached_query,
+    _set_bulk_cached_query_chunk,
     get_current_widget_specs,
     get_metric_extraction_config,
 )
@@ -766,24 +766,24 @@ def test_get_metric_extraction_config_alerts_and_widgets_off(default_project: Pr
 @django_db_all
 def test_get_metric_extraction_config_uses_cache_for_widgets(default_project: Project) -> None:
     # widgets should be skipped if the feature is off
-    original_set_bulk_cached_query = _set_bulk_cached_query
+    original_set_bulk_cached_query = _set_bulk_cached_query_chunk
 
     with (
         Feature({ON_DEMAND_METRICS: True, ON_DEMAND_METRICS_WIDGETS: True}),
         override_options({"on_demand_metrics.cache_should_use_on_demand": 1.0}),
         mock.patch(
-            "sentry.relay.config.metric_extraction._set_bulk_cached_query"
-        ) as mock_set_cache_spy,
+            "sentry.relay.config.metric_extraction._set_bulk_cached_query_chunk"
+        ) as mock_set_cache_chunk_spy,
     ):
-        mock_set_cache_spy.side_effect = original_set_bulk_cached_query
+        mock_set_cache_chunk_spy.side_effect = original_set_bulk_cached_query
         create_widget(["count()"], "transaction.duration:>=1000", default_project)
 
         get_metric_extraction_config(TimeChecker(timedelta(seconds=0)), default_project)
 
-        assert mock_set_cache_spy.call_count == 1
+        assert mock_set_cache_chunk_spy.call_count == 6  # One for each chunk
 
         get_metric_extraction_config(TimeChecker(timedelta(seconds=0)), default_project)
-        assert mock_set_cache_spy.call_count == 1
+        assert mock_set_cache_chunk_spy.call_count == 6
 
 
 @django_db_all