X-Git-Url: https://git.arvados.org/arvados.git/blobdiff_plain/03a016b1edff72e698474cd31a887530ea89b530..ffa1fd1fdf584c71e248e9bb7d523f788a517510:/sdk/go/httpserver/id_generator.go

diff --git a/sdk/go/httpserver/id_generator.go b/sdk/go/httpserver/id_generator.go
index c744691aa8..14d89873b6 100644
--- a/sdk/go/httpserver/id_generator.go
+++ b/sdk/go/httpserver/id_generator.go
@@ -5,12 +5,17 @@
 package httpserver
 
 import (
+	"math/rand"
 	"net/http"
 	"strconv"
 	"sync"
 	"time"
 )
 
+const (
+	HeaderRequestID = "X-Request-Id"
+)
+
 // IDGenerator generates alphanumeric strings suitable for use as
 // unique IDs (a given IDGenerator will never return the same ID
 // twice).
@@ -18,21 +23,24 @@ type IDGenerator struct {
 	// Prefix is prepended to each returned ID.
 	Prefix string
 
-	lastID int64
-	mtx    sync.Mutex
+	mtx sync.Mutex
+	src rand.Source
 }
 
 // Next returns a new ID string. It is safe to call Next from multiple
 // goroutines.
 func (g *IDGenerator) Next() string {
-	id := time.Now().UnixNano()
 	g.mtx.Lock()
-	if id <= g.lastID {
-		id = g.lastID + 1
+	defer g.mtx.Unlock()
+	if g.src == nil {
+		g.src = rand.NewSource(time.Now().UnixNano())
+	}
+	a, b := g.src.Int63(), g.src.Int63()
+	id := strconv.FormatInt(a, 36) + strconv.FormatInt(b, 36)
+	for len(id) > 20 {
+		id = id[:20]
 	}
-	g.lastID = id
-	g.mtx.Unlock()
-	return g.Prefix + strconv.FormatInt(id, 36)
+	return g.Prefix + id
 }
 
 // AddRequestIDs wraps an http.Handler, adding an X-Request-Id header
@@ -40,8 +48,11 @@ func (g *IDGenerator) Next() string {
 func AddRequestIDs(h http.Handler) http.Handler {
 	gen := &IDGenerator{Prefix: "req-"}
 	return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
-		if req.Header.Get("X-Request-Id") == "" {
-			req.Header.Set("X-Request-Id", gen.Next())
+		if req.Header.Get(HeaderRequestID) == "" {
+			if req.Header == nil {
+				req.Header = http.Header{}
+			}
+			req.Header.Set(HeaderRequestID, gen.Next())
 		}
 		h.ServeHTTP(w, req)
 	})