Fixed Uniqueness

Author: Sri Krishna Paritala

id.go

@@ -3,6 +3,7 @@ package idgen
 import (
 	"errors"
 	"io"
+	"math"
 	"math/rand"
 	"strings"
 	"sync"
@@ -35,7 +36,8 @@ func New(prefix string) string {
 
 var entropyPool = sync.Pool{
 	New: func() interface{} {
-		return ulid.Monotonic(rand.New(rand.NewSource(time.Now().UnixNano())), 0)
+		ns := time.Now().UnixNano()
+		return ulid.Monotonic(rand.New(rand.NewSource(ns)), uint64(ns)%math.MaxUint32)
 	},
 }
 

id_test.go

@@ -5,6 +5,7 @@ import (
 	"net/url"
 	"sort"
 	"strings"
+	"sync"
 	"testing"
 	"time"
 
@@ -52,6 +53,36 @@ func TestUniqueness(t *testing.T) {
 	}
 }
 
+func TestUniquenessParallel(t *testing.T) {
+	var wg sync.WaitGroup
+
+	ids := make(chan string, 1000)
+	for i := 0; i < 100; i++ {
+		go func(ids chan<- string) {
+			wg.Add(1)
+			defer wg.Done()
+
+			for i := 0; i < 100; i++ {
+				ids <- idgen.New("usr")
+			}
+		}(ids)
+	}
+
+	go func() {
+		wg.Wait()
+		close(ids)
+	}()
+
+	set := map[string]bool{}
+	for id := range ids {
+		if set[id] {
+			t.Errorf("generating repeated strings")
+		}
+
+		set[id] = true
+	}
+}
+
 func TestLexicalOrder(t *testing.T) {
 	var ii [1000]string
 	for k := range ii {