Improve the performance of the HTTP API for getting all regions (#1970)

Makefile

@@ -99,7 +99,7 @@ travis_coverage: export GO111MODULE=on
 travis_coverage:
 ifeq ("$(TRAVIS_COVERAGE)", "1")
 	@$(FAILPOINT_ENABLE)
-	CGO_ENABLED=1 ./scripts/retool do $(OVERALLS) -project=github.com/pingcap/pd -covermode=count -ignore='.git,vendor' -- -coverpkg=./... || { $(FAILPOINT_DISABLE); exit 1; }
+	CGO_ENABLED=1 ./scripts/retool do $(OVERALLS) -concurrency=8 -project=github.com/pingcap/pd -covermode=count -ignore='.git,vendor' -- -coverpkg=./... || { $(FAILPOINT_DISABLE); exit 1; }
 	@$(FAILPOINT_DISABLE)
 else
 	@echo "coverage only runs in travis."

server/api/region.go

@@ -45,23 +45,29 @@ type RegionInfo struct {
 
 // NewRegionInfo create a new api RegionInfo.
 func NewRegionInfo(r *core.RegionInfo) *RegionInfo {
+	return InitRegion(r, &RegionInfo{})
+}
+
+// InitRegion init a new api RegionInfo from the core.RegionInfo.
+func InitRegion(r *core.RegionInfo, s *RegionInfo) *RegionInfo {
 	if r == nil {
 		return nil
 	}
-	return &RegionInfo{
-		ID:              r.GetID(),
-		StartKey:        string(core.HexRegionKey(r.GetStartKey())),
-		EndKey:          string(core.HexRegionKey(r.GetEndKey())),
-		RegionEpoch:     r.GetRegionEpoch(),
-		Peers:           r.GetPeers(),
-		Leader:          r.GetLeader(),
-		DownPeers:       r.GetDownPeers(),
-		PendingPeers:    r.GetPendingPeers(),
-		WrittenBytes:    r.GetBytesWritten(),
-		ReadBytes:       r.GetBytesRead(),
-		ApproximateSize: r.GetApproximateSize(),
-		ApproximateKeys: r.GetApproximateKeys(),
-	}
+
+	s.ID = r.GetID()
+	s.StartKey = core.HexRegionKeyStr(r.GetStartKey())
+	s.EndKey = core.HexRegionKeyStr(r.GetEndKey())
+	s.RegionEpoch = r.GetRegionEpoch()
+	s.Peers = r.GetPeers()
+	s.Leader = r.GetLeader()
+	s.DownPeers = r.GetDownPeers()
+	s.PendingPeers = r.GetPendingPeers()
+	s.WrittenBytes = r.GetBytesWritten()
+	s.ReadBytes = r.GetBytesRead()
+	s.ApproximateSize = r.GetApproximateSize()
+	s.ApproximateKeys = r.GetApproximateKeys()
+
+	return s
 }
 
 // RegionsInfo contains some regions with the detailed region info.
@@ -126,13 +132,18 @@ func newRegionsHandler(svr *server.Server, rd *render.Render) *regionsHandler {
 }
 
 func convertToAPIRegions(regions []*core.RegionInfo) *RegionsInfo {
-	regionInfos := make([]*RegionInfo, len(regions))
+	regionInfos := make([]RegionInfo, len(regions))
+	regionInfosRefs := make([]*RegionInfo, len(regions))
+
+	for i := 0; i < len(regions); i++ {
+		regionInfosRefs[i] = &regionInfos[i]
+	}
 	for i, r := range regions {
-		regionInfos[i] = NewRegionInfo(r)
+		regionInfosRefs[i] = InitRegion(r, regionInfosRefs[i])
 	}
 	return &RegionsInfo{
 		Count:   len(regions),
-		Regions: regionInfos,
+		Regions: regionInfosRefs,
 	}
 }
 

server/api/region_test.go

@@ -14,10 +14,12 @@
 package api
 
 import (
+	"bytes"
 	"fmt"
 	"math/rand"
 	"net/url"
 	"sort"
+	"testing"
 
 	. "github.com/pingcap/check"
 	"github.com/pingcap/kvproto/pkg/metapb"
@@ -320,3 +322,70 @@ func (s *testGetRegionSuite) TestScanRegionByKey(c *C) {
 		c.Assert(v, Equals, regions.Regions[i].ID)
 	}
 }
+
+// Create n regions (0..n) of n stores (0..n).
+// Each region contains np peers, the first peer is the leader.
+// (copied from server/cluster_test.go)
+func newTestRegions() []*core.RegionInfo {
+	n := uint64(10000)
+	np := uint64(3)
+
+	regions := make([]*core.RegionInfo, 0, n)
+	for i := uint64(0); i < n; i++ {
+		peers := make([]*metapb.Peer, 0, np)
+		for j := uint64(0); j < np; j++ {
+			peer := &metapb.Peer{
+				Id: i*np + j,
+			}
+			peer.StoreId = (i + j) % n
+			peers = append(peers, peer)
+		}
+		region := &metapb.Region{
+			Id:          i,
+			Peers:       peers,
+			StartKey:    []byte(fmt.Sprintf("%d", i)),
+			EndKey:      []byte(fmt.Sprintf("%d", i+1)),
+			RegionEpoch: &metapb.RegionEpoch{ConfVer: 2, Version: 2},
+		}
+		regions = append(regions, core.NewRegionInfo(region, peers[0]))
+	}
+	return regions
+}
+
+func BenchmarkRenderJSON(b *testing.B) {
+	regionInfos := newTestRegions()
+	rd := createStreamingRender()
+	regions := convertToAPIRegions(regionInfos)
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		var buffer bytes.Buffer
+		rd.JSON(&buffer, 200, regions)
+	}
+}
+
+func BenchmarkConvertToAPIRegions(b *testing.B) {
+	regionInfos := newTestRegions()
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		regions := convertToAPIRegions(regionInfos)
+		_ = regions.Count
+	}
+}
+
+func BenchmarkHexRegionKey(b *testing.B) {
+	key := []byte("region_number_infinity")
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_ = core.HexRegionKey(key)
+	}
+}
+
+func BenchmarkHexRegionKeyStr(b *testing.B) {
+	key := []byte("region_number_infinity")
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_ = core.HexRegionKeyStr(key)
+	}
+}

server/api/router.go

@@ -22,12 +22,20 @@ import (
 	"github.com/unrolled/render"
 )
 
-const pingAPI = "/ping"
+func createStreamingRender() *render.Render {
+	return render.New(render.Options{
+		StreamingJSON: true,
+	})
+}
 
-func createRouter(prefix string, svr *server.Server) *mux.Router {
-	rd := render.New(render.Options{
+func createIndentRender() *render.Render {
+	return render.New(render.Options{
 		IndentJSON: true,
 	})
+}
+
+func createRouter(prefix string, svr *server.Server) *mux.Router {
+	rd := createIndentRender()
 
 	router := mux.NewRouter().PathPrefix(prefix).Subrouter()
 	handler := svr.GetHandler()
@@ -88,8 +96,11 @@ func createRouter(prefix string, svr *server.Server) *mux.Router {
 	router.HandleFunc("/api/v1/region/id/{id}", regionHandler.GetRegionByID).Methods("GET")
 	router.HandleFunc("/api/v1/region/key/{key}", regionHandler.GetRegionByKey).Methods("GET")
 
+	srd := createStreamingRender()
+	regionsAllHandler := newRegionsHandler(svr, srd)
+	router.HandleFunc("/api/v1/regions", regionsAllHandler.GetAll).Methods("GET")
+
 	regionsHandler := newRegionsHandler(svr, rd)
-	router.HandleFunc("/api/v1/regions", regionsHandler.GetAll).Methods("GET")
 	router.HandleFunc("/api/v1/regions/key", regionsHandler.ScanRegionsByKey).Methods("GET")
 	router.HandleFunc("/api/v1/regions/store/{id}", regionsHandler.GetStoreRegions).Methods("GET")
 	router.HandleFunc("/api/v1/regions/writeflow", regionsHandler.GetTopWriteFlow).Methods("GET")
@@ -136,7 +147,7 @@ func createRouter(prefix string, svr *server.Server) *mux.Router {
 	logHanler := newlogHandler(svr, rd)
 	router.HandleFunc("/api/v1/admin/log", logHanler.Handle).Methods("POST")
 
-	router.HandleFunc(pingAPI, func(w http.ResponseWriter, r *http.Request) {}).Methods("GET")
+	router.HandleFunc("/ping", func(w http.ResponseWriter, r *http.Request) {}).Methods("GET")
 	router.Handle("/health", newHealthHandler(svr, rd)).Methods("GET")
 	router.Handle("/diagnose", newDiagnoseHandler(svr, rd)).Methods("GET")
 	return router

server/core/region.go

@@ -20,6 +20,7 @@ import (
 	"math/rand"
 	"reflect"
 	"strings"
+	"unsafe"
 
 	"github.com/gogo/protobuf/proto"
 	"github.com/pingcap/kvproto/pkg/metapb"
@@ -816,10 +817,57 @@ func DiffRegionKeyInfo(origin *RegionInfo, other *RegionInfo) string {
 	return strings.Join(ret, ", ")
 }
 
+// String converts slice of bytes to string without copy.
+func String(b []byte) (s string) {
+	if len(b) == 0 {
+		return ""
+	}
+	pbytes := (*reflect.SliceHeader)(unsafe.Pointer(&b))
+	pstring := (*reflect.StringHeader)(unsafe.Pointer(&s))
+	pstring.Data = pbytes.Data
+	pstring.Len = pbytes.Len
+	return
+}
+
+// ToUpperASCIIInplace bytes.ToUpper but zero-cost
+func ToUpperASCIIInplace(s []byte) []byte {
+	hasLower := false
+	for i := 0; i < len(s); i++ {
+		c := s[i]
+		hasLower = hasLower || ('a' <= c && c <= 'z')
+	}
+
+	if !hasLower {
+		return s
+	}
+	var c byte
+	for i := 0; i < len(s); i++ {
+		c = s[i]
+		if 'a' <= c && c <= 'z' {
+			c -= 'a' - 'A'
+		}
+		s[i] = c
+	}
+	return s
+}
+
+// EncodeToString overrides hex.EncodeToString implementation. Difference: returns []byte, not string
+func EncodeToString(src []byte) []byte {
+	dst := make([]byte, hex.EncodedLen(len(src)))
+	hex.Encode(dst, src)
+	return dst
+}
+
 // HexRegionKey converts region key to hex format. Used for formating region in
 // logs.
 func HexRegionKey(key []byte) []byte {
-	return []byte(strings.ToUpper(hex.EncodeToString(key)))
+	return ToUpperASCIIInplace(EncodeToString(key))
+}
+
+// HexRegionKeyStr converts region key to hex format. Used for formating region in
+// logs.
+func HexRegionKeyStr(key []byte) string {
+	return String(HexRegionKey(key))
 }
 
 // RegionToHexMeta converts a region meta's keys to hex format. Used for formating