chore(ddsketch): consume DDSketch wire format without metric scalars

crates/asap_otel_proto/proto/sketchlib_delta/ddsketch_delta.proto

@@ -7,25 +7,28 @@
 // `asap_sketchlib` picks these up upstream this vendoring can be removed.
 //
 // See `sketches/DDSketch/delta.go::ApplyDelta` for the canonical
-// merge semantics — additive bucket counts, additive count + sum,
-// min (can only decrease) + max (can only increase) as lossless
-// scalars when changed.
+// merge semantics — additive bucket counts only. The DataPoint-level
+// METRIC scalars (count/sum/min/max) were dropped from the wire format
+// (ProjectASAP/sketchlib-go#243 / asap_sketchlib#57): the total count is
+// recoverable by summing the bucket counts and the remaining aggregates
+// are carried by controller-provisioned exact aggregations.
 
 syntax = "proto3";
 
 package sketchlib.v1;
 
 // DDSketchDelta carries only the buckets that changed above threshold.
-// count/sum are additive deltas; min/max are lossless scalars transmitted
-// only when they changed.
+// Bucket counts are additive. The former count/sum (tags 2-3) and
+// min/max scalars (tags 4-7) were removed from the wire format
+// (ProjectASAP/sketchlib-go#243): the count is recoverable by summing
+// the merged bucket counts; Sum/Min/Max move to exact aggregations.
 message DDSketchDelta {
-  repeated DDSketchBucketDelta buckets     = 1;
-  int64   d_count     = 2;
-  double  d_sum       = 3;
-  double  new_min     = 4;
-  double  new_max     = 5;
-  bool    min_changed = 6;
-  bool    max_changed = 7;
+  repeated DDSketchBucketDelta buckets = 1;
+
+  // Tags 2-3 previously carried the additive count/sum deltas and tags
+  // 4-7 the lossless min/max scalars + their changed flags. Dropped from
+  // the wire format (ProjectASAP/sketchlib-go#243).
+  reserved 2, 3, 4, 5, 6, 7;
 }
 
 // DDSketchBucketDelta is the delta for one log-scale bucket.

data_plane/benches/sketch_db.rs

@@ -52,10 +52,6 @@ fn encode_ddsketch(values: &[f64], alpha: f64) -> Vec<u8> {
         alpha: sk.alpha,
         store_counts: sk.store_counts.clone(),
         store_offset: sk.store_offset,
-        count: sk.count,
-        sum: sk.sum,
-        min: sk.min,
-        max: sk.max,
     };
     SketchEnvelope {
         sketch_state: Some(sketch_envelope::SketchState::Ddsketch(state)),

data_plane/examples/sketch_db_diag.rs

@@ -38,10 +38,6 @@ fn ddsketch_payload() -> Vec<u8> {
         alpha: sk.alpha,
         store_counts: sk.store_counts.clone(),
         store_offset: sk.store_offset,
-        count: sk.count,
-        sum: sk.sum,
-        min: sk.min,
-        max: sk.max,
     };
     SketchEnvelope {
         sketch_state: Some(sketch_envelope::SketchState::Ddsketch(state)),

data_plane/src/drivers/ingest/otel.rs

@@ -2580,9 +2580,11 @@ mod dispatcher_tests {
 
         // Base sketch represents the last full snapshot the agent sent.
         let mut acc: Box<dyn AggregateCore> = Box::new(DDSketchAccumulator {
-            inner: DdSketch::from_raw(0.01, vec![1, 2, 3], 0, 6, 12.0, 1.0, 3.0),
+            inner: DdSketch::from_raw(0.01, vec![1, 2, 3], 0),
         });
 
+        // The wire delta now carries only bucket deltas (tags 2-7
+        // reserved post ProjectASAP/sketchlib-go#243 / asap_sketchlib#57).
         let bytes = PbDelta {
             buckets: vec![
                 DdSketchBucketDelta {
@@ -2594,12 +2596,6 @@ mod dispatcher_tests {
                     d_count: 20,
                 },
             ],
-            d_count: 30,
-            d_sum: 70.0,
-            new_min: 0.5,
-            new_max: 5.0,
-            min_changed: true,
-            max_changed: true,
         }
         .encode_to_vec();
 
@@ -2613,9 +2609,8 @@ mod dispatcher_tests {
 
         let dd = acc.as_any().downcast_ref::<DDSketchAccumulator>().unwrap();
         assert_eq!(dd.inner.store_counts, vec![11, 2, 23]);
-        assert_eq!(dd.inner.count, 36);
-        assert_eq!(dd.inner.min, 0.5);
-        assert_eq!(dd.inner.max, 5.0);
+        // `count` recomputed from the merged buckets: 11 + 2 + 23 = 36.
+        assert_eq!(dd.inner.total_count(), 36);
     }
 
     #[test]

data_plane/src/precompute_engine/ingest_handler.rs

@@ -184,13 +184,15 @@ mod tests {
         // so we're not racing any earlier tests.
         let series_key = "__name__=latency_ms,inst=a";
         let base = DDSketchAccumulator {
-            inner: DdSketch::from_raw(0.01, vec![1, 2, 3], 0, 6, 12.0, 1.0, 3.0),
+            inner: DdSketch::from_raw(0.01, vec![1, 2, 3], 0),
         };
         state
             .sketch_snapshots
             .insert(series_key.to_string(), Box::new(base.clone()));
 
-        // First delta adds to bucket 0 and bucket 2.
+        // First delta adds to bucket 0 and bucket 2. The wire delta now
+        // carries only bucket deltas (the count/sum/min/max scalar fields
+        // were dropped, ProjectASAP/sketchlib-go#243 / asap_sketchlib#57).
         let d1 = PbDelta {
             buckets: vec![
                 DdSketchBucketDelta {
@@ -202,11 +204,6 @@ mod tests {
                     d_count: 20,
                 },
             ],
-            d_count: 30,
-            d_sum: 70.0,
-            new_max: 5.0,
-            max_changed: true,
-            ..Default::default()
         }
         .encode_to_vec();
         let mut acc1 = state
@@ -227,11 +224,6 @@ mod tests {
                 index: 1,
                 d_count: 5,
             }],
-            d_count: 5,
-            d_sum: 10.0,
-            new_max: 6.0,
-            max_changed: true,
-            ..Default::default()
         }
         .encode_to_vec();
         let mut acc2 = state
@@ -246,12 +238,10 @@ mod tests {
         // Base [1,2,3] + d1 [+10 on 0, +20 on 2] = [11,2,23];
         // + d2 [+5 on 1] = [11,7,23].
         assert_eq!(final_dd.inner.store_counts, vec![11, 7, 23]);
-        // Counts add: 6 + 30 + 5 = 41.
-        assert_eq!(final_dd.inner.count, 41);
-        // Sum: 12 + 70 + 10 = 92.
-        assert_eq!(final_dd.inner.sum, 92.0);
-        // Max updated to 6.0 via d2's max_changed flag.
-        assert_eq!(final_dd.inner.max, 6.0);
+        // `count` recomputed from the merged buckets: 11 + 7 + 23 = 41.
+        // (sum/min/max were dropped from the wire format,
+        // ProjectASAP/sketchlib-go#243 / asap_sketchlib#57.)
+        assert_eq!(final_dd.inner.total_count(), 41);
 
         drop(state);
         let _ = drain.await;