allocator: replace read amp with io thresh

We previously checked stores' L0-sublevels to exclude IO overloaded
stores from being allocation targets (cockroachdb#78608). This commit replaces the signal
with the normalized IO overload score instead, which also factors in the
L0-filecount. We started gossiping this value as of cockroachdb#83720. We continue
gossiping L0-sublevels for mixed-version compatibility; we can stop doing this
in 23.2.

Resolves: cockroachdb#85084

Release note (ops change): We've deprecated two cluster settings:
- kv.allocator.l0_sublevels_threshold
- kv.allocator.l0_sublevels_threshold_enforce.
The pair of them were used to control rebalancing and upreplication behavior in
the face of IO overloaded stores. This has been now been replaced by other
internal mechanisms.

pkg/kv/kvserver/allocator/allocatorimpl/BUILD.bazel

@@ -22,6 +22,7 @@ go_library(
         "//pkg/roachpb",
         "//pkg/settings",
         "//pkg/settings/cluster",
+        "//pkg/util/admission/admissionpb",
         "//pkg/util/log",
         "//pkg/util/metric",
         "//pkg/util/stop",

pkg/kv/kvserver/allocator/allocatorimpl/allocator.go

@@ -2085,16 +2085,16 @@ func (a *Allocator) leaseholderShouldMoveDueToPreferences(
 }
 
 // StoreHealthOptions returns the store health options, currently only
-// considering the threshold for L0 sub-levels. This threshold is not
+// considering the threshold for io overload. This threshold is not
 // considered in allocation or rebalancing decisions (excluding candidate
 // stores as targets) when enforcementLevel is set to storeHealthNoAction or
 // storeHealthLogOnly. By default storeHealthBlockRebalanceTo is the action taken. When
 // there is a mixed version cluster, storeHealthNoAction is set instead.
 func (a *Allocator) StoreHealthOptions(_ context.Context) StoreHealthOptions {
-	enforcementLevel := StoreHealthEnforcement(l0SublevelsThresholdEnforce.Get(&a.st.SV))
+	enforcementLevel := IOOverloadEnforcementLevel(IOOverloadThresholdEnforcement.Get(&a.st.SV))
 	return StoreHealthOptions{
 		EnforcementLevel:    enforcementLevel,
-		L0SublevelThreshold: l0SublevelsThreshold.Get(&a.st.SV),
+		IOOverloadThreshold: IOOverloadThreshold.Get(&a.st.SV),
 	}
 }
 

pkg/kv/kvserver/allocator/allocatorimpl/allocator_scorer_test.go

@@ -52,7 +52,7 @@ func TestOnlyValidAndHealthyDisk(t *testing.T) {
 	defer log.Scope(t).Close(t)
 
 	testCases := []struct {
-		valid, invalid, full, readAmpHigh int
+		valid, invalid, full, ioOverloaded int
 	}{
 		{0, 0, 0, 0},
 		{1, 0, 0, 0},
@@ -80,16 +80,16 @@ func TestOnlyValidAndHealthyDisk(t *testing.T) {
 			for i := 0; i < tc.full; i++ {
 				cl = append(cl, candidate{fullDisk: true})
 			}
-			for i := 0; i < tc.readAmpHigh; i++ {
-				cl = append(cl, candidate{highReadAmp: true})
+			for i := 0; i < tc.ioOverloaded; i++ {
+				cl = append(cl, candidate{ioOverloaded: true})
 			}
 			sort.Sort(sort.Reverse(byScore(cl)))
 
 			valid := cl.onlyValidAndHealthyDisk()
 			if a, e := len(valid), tc.valid; a != e {
 				t.Errorf("expected %d valid, actual %d", e, a)
 			}
-			if a, e := len(cl)-len(valid), tc.invalid+tc.full+tc.readAmpHigh; a != e {
+			if a, e := len(cl)-len(valid), tc.invalid+tc.full+tc.ioOverloaded; a != e {
 				t.Errorf("expected %d invalid, actual %d", e, a)
 			}
 		})
@@ -1096,7 +1096,7 @@ func TestShouldRebalanceDiversity(t *testing.T) {
 	defer leaktest.AfterTest(t)()
 	defer log.Scope(t).Close(t)
 
-	options := &RangeCountScorerOptions{StoreHealthOptions: StoreHealthOptions{EnforcementLevel: StoreHealthNoAction}}
+	options := &RangeCountScorerOptions{StoreHealthOptions: StoreHealthOptions{EnforcementLevel: IOOverloadThresholdNoAction}}
 	newStore := func(id int, locality roachpb.Locality) roachpb.StoreDescriptor {
 		return roachpb.StoreDescriptor{
 			StoreID: roachpb.StoreID(id),

pkg/kv/kvserver/allocator/storepool/store_pool.go

@@ -558,26 +558,34 @@ func (sp *StorePool) statusString(nl NodeLivenessFunc) string {
 // storeGossipUpdate is the Gossip callback used to keep the StorePool up to date.
 func (sp *StorePool) storeGossipUpdate(_ string, content roachpb.Value) {
 	var storeDesc roachpb.StoreDescriptor
-	// We keep copies of the capacity and storeID to pass into the
-	// capacityChanged callback.
-	var oldCapacity, curCapacity roachpb.StoreCapacity
-	var storeID roachpb.StoreID
 
 	if err := content.GetProto(&storeDesc); err != nil {
 		ctx := sp.AnnotateCtx(context.TODO())
 		log.Errorf(ctx, "%v", err)
 		return
 	}
-	storeID = storeDesc.StoreID
-	curCapacity = storeDesc.Capacity
+
+	sp.storeDescriptorUpdate(storeDesc)
+}
+
+// storeDescriptorUpdate takes a store descriptor and updates the corresponding
+// details for the store in the storepool.
+func (sp *StorePool) storeDescriptorUpdate(storeDesc roachpb.StoreDescriptor) {
+	// We keep copies of the capacity and storeID to pass into the
+	// capacityChanged callback.
+	var oldCapacity roachpb.StoreCapacity
+	storeID := storeDesc.StoreID
+	curCapacity := storeDesc.Capacity
+
+	now := sp.clock.PhysicalTime()
 
 	sp.DetailsMu.Lock()
 	detail := sp.GetStoreDetailLocked(storeID)
 	if detail.Desc != nil {
 		oldCapacity = detail.Desc.Capacity
 	}
 	detail.Desc = &storeDesc
-	detail.LastUpdatedTime = sp.clock.PhysicalTime()
+	detail.LastUpdatedTime = now
 	sp.DetailsMu.Unlock()
 
 	sp.localitiesMu.Lock()
@@ -749,8 +757,7 @@ func (sp *StorePool) UpdateLocalStoresAfterLeaseTransfer(
 	}
 }
 
-// newStoreDetail makes a new StoreDetail struct. It sets index to be -1 to
-// ensure that it will be processed by a queue immediately.
+// newStoreDetail makes a new StoreDetail struct.
 func newStoreDetail() *StoreDetail {
 	return &StoreDetail{}
 }
@@ -1063,9 +1070,9 @@ type StoreList struct {
 	// eligible to be rebalance targets.
 	candidateWritesPerSecond Stat
 
-	// candidateWritesPerSecond tracks L0 sub-level stats for Stores that are
-	// eligible to be rebalance targets.
-	CandidateL0Sublevels Stat
+	// CandidateIOOverloadScores tracks the IO overload stats for Stores that are
+	// eligible to be rebalance candidates.
+	CandidateIOOverloadScores Stat
 }
 
 // MakeStoreList constructs a new store list based on the passed in descriptors.
@@ -1080,8 +1087,9 @@ func MakeStoreList(descriptors []roachpb.StoreDescriptor) StoreList {
 		sl.candidateLogicalBytes.update(float64(desc.Capacity.LogicalBytes))
 		sl.CandidateQueriesPerSecond.update(desc.Capacity.QueriesPerSecond)
 		sl.candidateWritesPerSecond.update(desc.Capacity.WritesPerSecond)
-		sl.CandidateL0Sublevels.update(float64(desc.Capacity.L0Sublevels))
 		sl.CandidateCPU.update(desc.Capacity.CPUPerSecond)
+		score, _ := desc.Capacity.IOThreshold.Score()
+		sl.CandidateIOOverloadScores.update(score)
 	}
 	return sl
 }
@@ -1102,12 +1110,13 @@ func (sl StoreList) String() string {
 		fmt.Fprintf(&buf, " <no candidates>")
 	}
 	for _, desc := range sl.Stores {
-		fmt.Fprintf(&buf, "  %d: ranges=%d leases=%d disk-usage=%s queries-per-second=%.2f store-cpu-per-second=%s l0-sublevels=%d\n",
+		ioScore, _ := desc.Capacity.IOThreshold.Score()
+		fmt.Fprintf(&buf, "  %d: ranges=%d leases=%d disk-usage=%s queries-per-second=%.2f store-cpu-per-second=%s io-overload=%.2f\n",
 			desc.StoreID, desc.Capacity.RangeCount,
 			desc.Capacity.LeaseCount, humanizeutil.IBytes(desc.Capacity.LogicalBytes),
 			desc.Capacity.QueriesPerSecond,
 			humanizeutil.Duration(time.Duration(int64(desc.Capacity.CPUPerSecond))),
-			desc.Capacity.L0Sublevels,
+			ioScore,
 		)
 	}
 	return buf.String()

pkg/kv/kvserver/metrics.go

@@ -2607,9 +2607,9 @@ func newStoreMetrics(histogramWindow time.Duration) *StoreMetrics {
 		// L0SublevelsMax. this is not exported to as metric.
 		sm.l0SublevelsTracker.swag = slidingwindow.NewMaxSwag(
 			timeutil.Now(),
-			allocatorimpl.L0SublevelInterval,
-			// 5 sliding windows, by the default interval (2 mins) will track the
-			// maximum for up to 10 minutes. Selected experimentally.
+			// Use 5 sliding windows, so the retention period is divided by 5 to
+			// calculate the interval of the sliding window buckets.
+			allocatorimpl.L0SublevelTrackerRetention/5,
 			5,
 		)
 	}
@@ -2693,17 +2693,16 @@ func (sm *StoreMetrics) updateEngineMetrics(m storage.Metrics) {
 	sm.DiskStalled.Update(m.DiskStallCount)
 	sm.SharedStorageBytesRead.Update(m.SharedStorageReadBytes)
 	sm.SharedStorageBytesWritten.Update(m.SharedStorageWriteBytes)
-
+	sm.RdbL0Sublevels.Update(int64(m.Levels[0].Sublevels))
+	sm.RdbL0NumFiles.Update(m.Levels[0].NumFiles)
+	sm.RdbL0BytesFlushed.Update(int64(m.Levels[0].BytesFlushed))
 	// Update the maximum number of L0 sub-levels seen.
 	sm.l0SublevelsTracker.Lock()
 	sm.l0SublevelsTracker.swag.Record(timeutil.Now(), float64(m.Levels[0].Sublevels))
 	curMax, _ := sm.l0SublevelsTracker.swag.Query(timeutil.Now())
 	sm.l0SublevelsTracker.Unlock()
 	syncutil.StoreFloat64(&sm.l0SublevelsWindowedMax, curMax)
 
-	sm.RdbL0Sublevels.Update(int64(m.Levels[0].Sublevels))
-	sm.RdbL0NumFiles.Update(m.Levels[0].NumFiles)
-	sm.RdbL0BytesFlushed.Update(int64(m.Levels[0].BytesFlushed))
 	for level, stats := range m.Levels {
 		sm.RdbBytesIngested[level].Update(int64(stats.BytesIngested))
 		sm.RdbLevelSize[level].Update(stats.Size)

pkg/kv/kvserver/store_pool_test.go

@@ -25,6 +25,7 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/storage"
 	"github.com/cockroachdb/cockroach/pkg/storage/enginepb"
 	"github.com/cockroachdb/cockroach/pkg/testutils/gossiputil"
+	"github.com/cockroachdb/cockroach/pkg/util/admission/admissionpb"
 	"github.com/cockroachdb/cockroach/pkg/util/hlc"
 	"github.com/cockroachdb/cockroach/pkg/util/leaktest"
 	"github.com/cockroachdb/cockroach/pkg/util/log"
@@ -60,7 +61,12 @@ func TestStorePoolUpdateLocalStore(t *testing.T) {
 				LogicalBytes:     30,
 				QueriesPerSecond: 100,
 				WritesPerSecond:  30,
-				L0Sublevels:      4,
+				IOThreshold: admissionpb.IOThreshold{
+					L0NumSubLevels:          5,
+					L0NumSubLevelsThreshold: 20,
+					L0NumFiles:              5,
+					L0NumFilesThreshold:     1000,
+				},
 			},
 		},
 		{
@@ -74,7 +80,12 @@ func TestStorePoolUpdateLocalStore(t *testing.T) {
 				LogicalBytes:     25,
 				QueriesPerSecond: 50,
 				WritesPerSecond:  25,
-				L0Sublevels:      8,
+				IOThreshold: admissionpb.IOThreshold{
+					L0NumSubLevels:          10,
+					L0NumSubLevelsThreshold: 20,
+					L0NumFiles:              10,
+					L0NumFilesThreshold:     1000,
+				},
 			},
 		},
 	}
@@ -130,8 +141,8 @@ func TestStorePoolUpdateLocalStore(t *testing.T) {
 	if expectedWPS := 30 + WPS; desc.Capacity.WritesPerSecond != expectedWPS {
 		t.Errorf("expected WritesPerSecond %f, but got %f", expectedWPS, desc.Capacity.WritesPerSecond)
 	}
-	if expectedL0Sublevels := int64(4); desc.Capacity.L0Sublevels != expectedL0Sublevels {
-		t.Errorf("expected L0 Sub-Levels %d, but got %d", expectedL0Sublevels, desc.Capacity.L0Sublevels)
+	if expectedNumL0Sublevels := int64(5); desc.Capacity.IOThreshold.L0NumSubLevels != expectedNumL0Sublevels {
+		t.Errorf("expected L0 Sub-Levels %d, but got %d", expectedNumL0Sublevels, desc.Capacity.IOThreshold.L0NumFiles)
 	}
 
 	sp.UpdateLocalStoreAfterRebalance(roachpb.StoreID(2), rangeUsageInfo, roachpb.REMOVE_VOTER)
@@ -151,8 +162,8 @@ func TestStorePoolUpdateLocalStore(t *testing.T) {
 	if expectedWPS := 25 - WPS; desc.Capacity.WritesPerSecond != expectedWPS {
 		t.Errorf("expected WritesPerSecond %f, but got %f", expectedWPS, desc.Capacity.WritesPerSecond)
 	}
-	if expectedL0Sublevels := int64(8); desc.Capacity.L0Sublevels != expectedL0Sublevels {
-		t.Errorf("expected L0 Sub-Levels %d, but got %d", expectedL0Sublevels, desc.Capacity.L0Sublevels)
+	if expectedNumL0Sublevels := int64(10); desc.Capacity.IOThreshold.L0NumSubLevels != expectedNumL0Sublevels {
+		t.Errorf("expected L0 Sub-Levels %d, but got %d", expectedNumL0Sublevels, desc.Capacity.IOThreshold.L0NumFiles)
 	}
 
 	sp.UpdateLocalStoresAfterLeaseTransfer(roachpb.StoreID(1), roachpb.StoreID(2), rangeUsageInfo)