Initial commit

library/stat/summary/BUILD

@@ -0,0 +1,38 @@
+package(default_visibility = ["//visibility:public"])
+
+load(
+    "@io_bazel_rules_go//go:def.bzl",
+    "go_test",
+    "go_library",
+)
+
+go_test(
+    name = "go_default_test",
+    srcs = ["summary_test.go"],
+    embed = [":go_default_library"],
+    rundir = ".",
+    tags = ["automanaged"],
+    deps = ["//vendor/github.com/stretchr/testify/assert:go_default_library"],
+)
+
+go_library(
+    name = "go_default_library",
+    srcs = ["summary.go"],
+    importpath = "go-common/library/stat/summary",
+    tags = ["automanaged"],
+    visibility = ["//visibility:public"],
+)
+
+filegroup(
+    name = "package-srcs",
+    srcs = glob(["**"]),
+    tags = ["automanaged"],
+    visibility = ["//visibility:private"],
+)
+
+filegroup(
+    name = "all-srcs",
+    srcs = [":package-srcs"],
+    tags = ["automanaged"],
+    visibility = ["//visibility:public"],
+)

library/stat/summary/summary.go

@@ -0,0 +1,129 @@
+package summary
+
+import (
+	"sync"
+	"time"
+)
+
+type bucket struct {
+	val   int64
+	count int64
+	next  *bucket
+}
+
+func (b *bucket) Add(val int64) {
+	b.val += val
+	b.count++
+}
+
+func (b *bucket) Value() (int64, int64) {
+	return b.val, b.count
+}
+
+func (b *bucket) Reset() {
+	b.val = 0
+	b.count = 0
+}
+
+// Summary is a summary interface.
+type Summary interface {
+	Add(int64)
+	Reset()
+	Value() (val int64, cnt int64)
+}
+
+type summary struct {
+	mu         sync.RWMutex
+	buckets    []bucket
+	bucketTime int64
+	lastAccess int64
+	cur        *bucket
+}
+
+// New new a summary.
+//
+// use RollingCounter creates a new window. windowTime is the time covering the entire
+// window. windowBuckets is the number of buckets the window is divided into.
+// An example: a 10 second window with 10 buckets will have 10 buckets covering
+// 1 second each.
+func New(window time.Duration, winBucket int) Summary {
+	buckets := make([]bucket, winBucket)
+	bucket := &buckets[0]
+	for i := 1; i < winBucket; i++ {
+		bucket.next = &buckets[i]
+		bucket = bucket.next
+	}
+	bucket.next = &buckets[0]
+	bucketTime := time.Duration(window.Nanoseconds() / int64(winBucket))
+	return &summary{
+		cur:        &buckets[0],
+		buckets:    buckets,
+		bucketTime: int64(bucketTime),
+		lastAccess: time.Now().UnixNano(),
+	}
+}
+
+// Add increments the summary by value.
+func (s *summary) Add(val int64) {
+	s.mu.Lock()
+	s.lastBucket().Add(val)
+	s.mu.Unlock()
+}
+
+// Value get the summary value and count.
+func (s *summary) Value() (val int64, cnt int64) {
+	now := time.Now().UnixNano()
+	s.mu.RLock()
+	b := s.cur
+	i := s.elapsed(now)
+	for j := 0; j < len(s.buckets); j++ {
+		// skip all future reset bucket.
+		if i > 0 {
+			i--
+		} else {
+			v, c := b.Value()
+			val += v
+			cnt += c
+		}
+		b = b.next
+	}
+	s.mu.RUnlock()
+	return
+}
+
+//  Reset reset the counter.
+func (s *summary) Reset() {
+	s.mu.Lock()
+	for i := range s.buckets {
+		s.buckets[i].Reset()
+	}
+	s.mu.Unlock()
+}
+
+func (s *summary) elapsed(now int64) (i int) {
+	var e int64
+	if e = now - s.lastAccess; e <= s.bucketTime {
+		return
+	}
+	if i = int(e / s.bucketTime); i > len(s.buckets) {
+		i = len(s.buckets)
+	}
+	return
+}
+
+func (s *summary) lastBucket() (b *bucket) {
+	now := time.Now().UnixNano()
+	b = s.cur
+	// reset the buckets between now and number of buckets ago. If
+	// that is more that the existing buckets, reset all.
+	if i := s.elapsed(now); i > 0 {
+		s.lastAccess = now
+		for ; i > 0; i-- {
+			// replace the next used bucket.
+			b = b.next
+			b.Reset()
+		}
+	}
+	s.cur = b
+	return
+}

library/stat/summary/summary_test.go

@@ -0,0 +1,69 @@
+package summary
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestSummaryMinInterval(t *testing.T) {
+	count := New(time.Second/2, 10)
+	tk1 := time.NewTicker(5 * time.Millisecond)
+	defer tk1.Stop()
+	for i := 0; i < 100; i++ {
+		<-tk1.C
+		count.Add(2)
+	}
+
+	v, c := count.Value()
+	t.Logf("count value: %d, %d\n", v, c)
+	// 10% of error when bucket is 10
+	if v < 190 || v > 210 {
+		t.Errorf("expect value in [90-110] get %d", v)
+	}
+	// 10% of error when bucket is 10
+	if c < 90 || c > 110 {
+		t.Errorf("expect value in [90-110] get %d", v)
+	}
+}
+
+func TestSummary(t *testing.T) {
+	s := New(time.Second, 10)
+
+	t.Run("add", func(t *testing.T) {
+		s.Add(1)
+		v, c := s.Value()
+		assert.Equal(t, v, int64(1))
+		assert.Equal(t, c, int64(1))
+	})
+	time.Sleep(time.Millisecond * 110)
+	t.Run("add2", func(t *testing.T) {
+		s.Add(1)
+		v, c := s.Value()
+		assert.Equal(t, v, int64(2))
+		assert.Equal(t, c, int64(2))
+	})
+	time.Sleep(time.Millisecond * 900) // expire one bucket, 110 + 900
+	t.Run("expire", func(t *testing.T) {
+		v, c := s.Value()
+		assert.Equal(t, v, int64(1))
+		assert.Equal(t, c, int64(1))
+		s.Add(1)
+		v, c = s.Value()
+		assert.Equal(t, v, int64(2)) // expire one bucket
+		assert.Equal(t, c, int64(2)) // expire one bucket
+	})
+	time.Sleep(time.Millisecond * 1100)
+	t.Run("expire_all", func(t *testing.T) {
+		v, c := s.Value()
+		assert.Equal(t, v, int64(0))
+		assert.Equal(t, c, int64(0))
+	})
+	t.Run("reset", func(t *testing.T) {
+		s.Reset()
+		v, c := s.Value()
+		assert.Equal(t, v, int64(0))
+		assert.Equal(t, c, int64(0))
+	})
+}