kvserver: gossip l0sublevels instead of read amp

pkg/kv/kvserver/store.go

@@ -2966,7 +2966,7 @@ func (s *Store) Capacity(ctx context.Context, useCached bool) (roachpb.StoreCapa
  capacity.LogicalBytes = logicalBytes
  capacity.QueriesPerSecond = totalQueriesPerSecond
  capacity.WritesPerSecond = totalWritesPerSecond
- capacity.ReadAmplification = s.metrics.RdbReadAmplification.Value()
+ capacity.L0Sublevels = s.metrics.RdbL0Sublevels.Value()
  capacity.BytesPerReplica = roachpb.PercentilesFromData(bytesPerReplica)
  capacity.WritesPerReplica = roachpb.PercentilesFromData(writesPerReplica)
  s.recordNewPerSecondStats(totalQueriesPerSecond, totalWritesPerSecond)

pkg/kv/kvserver/store_pool.go

@@ -755,10 +755,6 @@ type StoreList struct {
  // candidateWritesPerSecond tracks writes-per-second stats for stores that are
  // eligible to be rebalance targets.
  candidateWritesPerSecond stat
-
- // candidateReadAmplification tracks the read amplification stats for stores that are
- // eligible to be rebalance targets.
- candidateReadAmplification stat
 }
 
 // Generates a new store list based on the passed in descriptors. It will
@@ -773,32 +769,30 @@ 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.candidateReadAmplification.update(float64(desc.Capacity.ReadAmplification))
  }
  return sl
 }
 
 func (sl StoreList) String() string {
  var buf bytes.Buffer
  fmt.Fprintf(&buf,
- " candidate: avg-ranges=%v avg-leases=%v avg-disk-usage=%v avg-queries-per-second=%v read-amplification=%v",
+ " candidate: avg-ranges=%v avg-leases=%v avg-disk-usage=%v avg-queries-per-second=%v",
  sl.candidateRanges.mean,
  sl.candidateLeases.mean,
  humanizeutil.IBytes(int64(sl.candidateLogicalBytes.mean)),
  sl.candidateQueriesPerSecond.mean,
- sl.candidateReadAmplification.mean,
  )
  if len(sl.stores) > 0 {
  fmt.Fprintf(&buf, "\n")
  } else {
  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 read-amplification=%d\n",
+ fmt.Fprintf(&buf, " %d: ranges=%d leases=%d disk-usage=%s queries-per-second=%.2f l0-sublevels=%d\n",
  desc.StoreID, desc.Capacity.RangeCount,
  desc.Capacity.LeaseCount, humanizeutil.IBytes(desc.Capacity.LogicalBytes),
  desc.Capacity.QueriesPerSecond,
- desc.Capacity.ReadAmplification,
+ desc.Capacity.L0Sublevels,
  )
  }
  return buf.String()

pkg/kv/kvserver/store_pool_test.go

@@ -513,28 +513,28 @@ func TestStorePoolUpdateLocalStore(t *testing.T) {
  StoreID: 1,
  Node: roachpb.NodeDescriptor{NodeID: 1},
  Capacity: roachpb.StoreCapacity{
- Capacity:  100,
- Available:  50,
- RangeCount:  5,
- LeaseCount:  1,
- LogicalBytes:  30,
- QueriesPerSecond:  100,
- WritesPerSecond:  30,
- ReadAmplification: 5,
+ Capacity: 100,
+ Available: 50,
+ RangeCount: 5,
+ LeaseCount: 1,
+ LogicalBytes: 30,
+ QueriesPerSecond: 100,
+ WritesPerSecond: 30,
+ L0Sublevels: 4,
  },
  },
  {
  StoreID: 2,
  Node: roachpb.NodeDescriptor{NodeID: 2},
  Capacity: roachpb.StoreCapacity{
- Capacity:  100,
- Available:  55,
- RangeCount:  4,
- LeaseCount:  2,
- LogicalBytes:  25,
- QueriesPerSecond:  50,
- WritesPerSecond:  25,
- ReadAmplification: 10,
+ Capacity: 100,
+ Available: 55,
+ RangeCount: 4,
+ LeaseCount: 2,
+ LogicalBytes: 25,
+ QueriesPerSecond: 50,
+ WritesPerSecond: 25,
+ L0Sublevels: 8,
  },
  },
  }
@@ -576,8 +576,8 @@ 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 expectedReadAmp := int64(5); desc.Capacity.ReadAmplification != expectedReadAmp {
- t.Errorf("expected ReadAmplification %d, but got %d", expectedReadAmp, desc.Capacity.ReadAmplification)
+ if expectedL0Sublevels := int64(4); desc.Capacity.L0Sublevels != expectedL0Sublevels {
+ t.Errorf("expected L0 Sub-Levels %d, but got %d", expectedL0Sublevels, desc.Capacity.L0Sublevels)
  }
 
  sp.updateLocalStoreAfterRebalance(roachpb.StoreID(2), rangeUsageInfo, roachpb.REMOVE_VOTER)
@@ -597,8 +597,8 @@ 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 expectedReadAmp := int64(10); desc.Capacity.ReadAmplification != expectedReadAmp {
- t.Errorf("expected ReadAmplification %d, but got %d", expectedReadAmp, desc.Capacity.ReadAmplification)
+ if expectedL0Sublevels := int64(8); desc.Capacity.L0Sublevels != expectedL0Sublevels {
+ t.Errorf("expected L0 Sub-Levels %d, but got %d", expectedL0Sublevels, desc.Capacity.L0Sublevels)
  }
 
  sp.updateLocalStoresAfterLeaseTransfer(roachpb.StoreID(1), roachpb.StoreID(2), rangeUsageInfo.QueriesPerSecond)

pkg/roachpb/metadata.go

@@ -570,12 +570,12 @@ func (sc StoreCapacity) String() string {
 // SafeFormat implements the redact.SafeFormatter interface.
 func (sc StoreCapacity) SafeFormat(w redact.SafePrinter, _ rune) {
  w.Printf("disk (capacity=%s, available=%s, used=%s, logicalBytes=%s), "+
- "ranges=%d, leases=%d, queries=%.2f, writes=%.2f, readAmplification=%d"+
- "bytesPerReplica={%s}, writesPerReplica={%s}",
+ "ranges=%d, leases=%d, queries=%.2f, writes=%.2f, "+
+ "l0Sublevels=%d, bytesPerReplica={%s}, writesPerReplica={%s}",
  humanizeutil.IBytes(sc.Capacity), humanizeutil.IBytes(sc.Available),
  humanizeutil.IBytes(sc.Used), humanizeutil.IBytes(sc.LogicalBytes),
  sc.RangeCount, sc.LeaseCount, sc.QueriesPerSecond, sc.WritesPerSecond,
- sc.ReadAmplification, sc.BytesPerReplica, sc.WritesPerReplica)
+ sc.L0Sublevels, sc.BytesPerReplica, sc.WritesPerReplica)
 }
 
 // FractionUsed computes the fraction of storage capacity that is in use.

pkg/roachpb/metadata.proto

@@ -330,16 +330,17 @@ message StoreCapacity {
  // by ranges in the store. The stat is tracked over the time period defined
  // in storage/replica_stats.go, which as of July 2018 is 30 minutes.
  optional double writes_per_second = 5 [(gogoproto.nullable) = false];
- // read_amplification tracks the current read amplification in the store.
+ // l0_sublevels tracks the current number of l0 sublevels in the store.
  // TODO(kvoli): Use of this field will need to be version-gated, to avoid
  // instances where overlapping node-binary versions within a cluster result
  // in this this field missing.
- optional int64 read_amplification = 11 [(gogoproto.nullable) = false];
+ optional int64 l0_sublevels = 12 [(gogoproto.nullable) = false];
  // bytes_per_replica and writes_per_replica contain percentiles for the
  // number of bytes and writes-per-second to each replica in the store.
  // This information can be used for rebalancing decisions.
  optional Percentiles bytes_per_replica = 6 [(gogoproto.nullable) = false];
  optional Percentiles writes_per_replica = 7 [(gogoproto.nullable) = false];
+ reserved 11;
 }
 
 // StoreProperties contains configuration and OS-level details for a storage device.