Draft datatype for seat-seconds

staging/src/k8s.io/apiserver/pkg/util/flowcontrol/fairqueuing/queueset/seatsecs_test.go

@@ -0,0 +1,45 @@
+/*
+Copyright 2021 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package queueset
+
+import (
+	"fmt"
+	"math"
+	"testing"
+	"time"
+)
+
+func TestSeatSecondsString(t *testing.T) {
+	digits := math.Log10(ssScale)
+	expectFmt := fmt.Sprintf("%%%d.%dfss", int(digits+2), int(digits))
+	testCases := []struct {
+		ss     SeatSeconds
+		expect string
+	}{
+		{ss: SeatSeconds(1), expect: fmt.Sprintf(expectFmt, 1.0/ssScale)},
+		{ss: 0, expect: "0.00000000ss"},
+		{ss: SeatsTimesDuration(1, time.Second), expect: "1.00000000ss"},
+		{ss: SeatsTimesDuration(123, 100*time.Millisecond), expect: "12.30000000ss"},
+		{ss: SeatsTimesDuration(1203, 10*time.Millisecond), expect: "12.03000000ss"},
+	}
+	for _, testCase := range testCases {
+		actualStr := testCase.ss.String()
+		if actualStr != testCase.expect {
+			t.Errorf("SeatSeonds(%d) formatted as %q rather than expected %q", uint64(testCase.ss), actualStr, testCase.expect)
+		}
+	}
+}

staging/src/k8s.io/apiserver/pkg/util/flowcontrol/fairqueuing/queueset/types.go

@@ -18,6 +18,8 @@ package queueset
 
 import (
 	"context"
+	"fmt"
+	"math"
 	"time"
 
 	genericrequest "k8s.io/apiserver/pkg/endpoints/request"
@@ -134,3 +136,39 @@ func (q *queue) dump(includeDetails bool) debug.QueueDump {
 		SeatsInUse:        q.seatsInUse,
 	}
 }
+
+// SeatSeconds is a measure of work, in units of seat-seconds, using a fixed-point representation.
+// `SeatSeconds(n)` represents `n/ssScale` seat-seconds.
+// The constants `ssScale` and `ssScaleDigits` are private to the implementation here,
+// no other code should use them.
+type SeatSeconds uint64
+
+// MaxSeatsSeconds is the maximum representable value of SeatSeconds
+const MaxSeatSeconds = SeatSeconds(math.MaxUint64)
+
+// MinSeatSeconds is the lowest representable value of SeatSeconds
+const MinSeatSeconds = SeatSeconds(0)
+
+// SeatsTimeDuration produces the SeatSeconds value for the given factors.
+// This is intended only to produce small values, increments in work
+// rather than amount of work done since process start.
+func SeatsTimesDuration(seats float64, duration time.Duration) SeatSeconds {
+	return SeatSeconds(math.Round(seats * float64(duration/time.Nanosecond) / (1e9 / ssScale)))
+}
+
+// ToFloat converts to a floating-point representation.
+// This conversion may lose precision.
+func (ss SeatSeconds) ToFloat() float64 {
+	return float64(ss) / ssScale
+}
+
+// String converts to a string.
+// This is suitable for large as well as small values.
+func (ss SeatSeconds) String() string {
+	const div = SeatSeconds(ssScale)
+	quo := ss / div
+	rem := ss - quo*div
+	return fmt.Sprintf("%d.%08dss", quo, rem)
+}
+
+const ssScale = 1e8