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kvserver: alter balanceScore result to classify stores into 3 buckets #73614

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Dec 17, 2021
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kvserver: alter balanceScore result to classify stores into 3 buckets #73614

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25 changes: 9 additions & 16 deletions pkg/kv/kvserver/allocator_scorer.go
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Original file line number Diff line number Diff line change
Expand Up @@ -102,8 +102,8 @@ type scorerOptions interface {
ctx context.Context, store roachpb.StoreDescriptor, sl StoreList,
) bool
// balanceScore returns a discrete score (`balanceStatus`) based on whether
// the store represented by `sc` classifies as underfull, lessThanEqualToMean,
// moreThanMean or overfull relative to all the stores in `sl`.
// the store represented by `sc` classifies as underfull, aroundTheMean, or
// overfull relative to all the stores in `sl`.
balanceScore(sl StoreList, sc roachpb.StoreCapacity) balanceStatus
// rebalanceFromConvergenceScore assigns a convergence score to the store
// referred to by `sc` based on whether moving a replica away from this store
Expand Down Expand Up @@ -172,13 +172,10 @@ func (o rangeCountScorerOptions) balanceScore(
curRangeCount := float64(sc.RangeCount)
if curRangeCount < minRangeCount {
return underfull
} else if curRangeCount <= sl.candidateRanges.mean {
return lessThanEqualToMean
} else if curRangeCount < maxRangeCount {
return moreThanMean
} else {
} else if curRangeCount >= maxRangeCount {
return overfull
}
return aroundTheMean
}

// rebalanceFromConvergesScore returns 1 iff rebalancing a replica away from
Expand Down Expand Up @@ -271,13 +268,10 @@ func (o qpsScorerOptions) balanceScore(sl StoreList, sc roachpb.StoreCapacity) b
curQPS := sc.QueriesPerSecond
if curQPS < minQPS {
return underfull
} else if curQPS <= sl.candidateQueriesPerSecond.mean {
return lessThanEqualToMean
} else if curQPS < maxQPS {
return moreThanMean
} else {
} else if curQPS >= maxQPS {
return overfull
}
return aroundTheMean
}

func (o qpsScorerOptions) rebalanceFromConvergesScore(_ StoreList, _ roachpb.StoreCapacity) int {
Expand Down Expand Up @@ -1523,10 +1517,9 @@ func diversityRebalanceFromScore(
type balanceStatus int

const (
overfull balanceStatus = -2
moreThanMean balanceStatus = -1
lessThanEqualToMean balanceStatus = 0
underfull balanceStatus = 1
overfull balanceStatus = -1
aroundTheMean balanceStatus = 0
underfull balanceStatus = 1
)

func overfullRangeThreshold(options rangeCountScorerOptions, mean float64) float64 {
Expand Down
57 changes: 20 additions & 37 deletions pkg/kv/kvserver/allocator_scorer_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1473,40 +1473,23 @@ func TestBalanceScoreByRangeCount(t *testing.T) {
candidateRanges: stat{mean: 1000},
}

sEmpty := roachpb.StoreCapacity{
Capacity: 1024 * 1024 * 1024,
Available: 1024 * 1024 * 1024,
LogicalBytes: 0,
}
sMean := roachpb.StoreCapacity{
Capacity: 1024 * 1024 * 1024,
Available: 512 * 1024 * 1024,
LogicalBytes: 512 * 1024 * 1024,
RangeCount: 1000,
}
sRangesOverfull := sMean
sRangesOverfull.RangeCount = 1500
sRangesUnderfull := sMean
sRangesUnderfull.RangeCount = 500
sRangesLessThanMean := sMean
sRangesLessThanMean.RangeCount = 900
sRangesMoreThanMean := sMean
sRangesMoreThanMean.RangeCount = 1099

testCases := []struct {
sc roachpb.StoreCapacity
expected balanceStatus
RangeCount int32
expected balanceStatus
}{
{sEmpty, underfull},
{sRangesLessThanMean, lessThanEqualToMean},
{sMean, lessThanEqualToMean},
{sRangesMoreThanMean, moreThanMean},
{sRangesOverfull, overfull},
{sRangesUnderfull, underfull},
{0, underfull},
{900, aroundTheMean},
{1000, aroundTheMean},
{1099, aroundTheMean},
{1100, overfull},
{2000, overfull},
}
for i, tc := range testCases {
if a, e := options.balanceScore(storeList, tc.sc), tc.expected; a != e {
t.Errorf("%d: balanceScore(storeList, %+v) got %d; want %d", i, tc.sc, a, e)
sc := roachpb.StoreCapacity{
RangeCount: tc.RangeCount,
}
if a, e := options.balanceScore(storeList, sc), tc.expected; a != e {
t.Errorf("%d: balanceScore(storeList, %+v) got %d; want %d", i, sc, a, e)
}
}
}
Expand All @@ -1518,26 +1501,26 @@ func TestRebalanceBalanceScoreOnQPS(t *testing.T) {
storeList := StoreList{
candidateQueriesPerSecond: stat{mean: 1000},
}
options := qpsScorerOptions{
qpsRebalanceThreshold: 0.1,
}

testCases := []struct {
QPS float64
expBalanceScore balanceStatus
}{
{0, underfull},
{900, lessThanEqualToMean},
{999, lessThanEqualToMean},
{1000, lessThanEqualToMean},
{1001, moreThanMean},
{899, underfull},
{900, aroundTheMean},
{1099, aroundTheMean},
{1100, overfull},
{2000, overfull},
}

for i, tc := range testCases {
sc := roachpb.StoreCapacity{
QueriesPerSecond: tc.QPS,
}
options := qpsScorerOptions{
qpsRebalanceThreshold: 0.1,
}
if a, e := options.balanceScore(storeList, sc), tc.expBalanceScore; a != e {
t.Errorf("%d: rebalanceToConvergesScore(storeList, %+v) got %d; want %d", i, sc, a, e)
}
Expand Down
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