enhance: Optimize save colelction target latency (#38345)

issue: #38237
this PR only use better compression level for proto msg which is larger
than 1MB, and use a lighter compression level for smaller proto msg,
which could get a better latency in most case.

this PR could reduce the latency from 22.7s to 4.7s with 10000
collctions and each collections has 1000 segments.

before this PR:
BenchmarkTargetManager-8 1 22781536357 ns/op 566407275088 B/op 11188282
allocs/op
after this PR:
BenchmarkTargetManager-8 1 4729566944 ns/op 36713248864 B/op 10963615
allocs/op

Signed-off-by: Wei Liu <wei.liu@zilliz.com>

internal/metastore/kv/querycoord/kv_catalog.go

@@ -279,8 +279,14 @@ func (s Catalog) SaveCollectionTargets(ctx context.Context, targets ...*querypb.
 		if err != nil {
 			return err
 		}
+
+		// only compress data when size is larger than 1MB
+		compressLevel := zstd.SpeedFastest
+		if len(v) > 1024*1024 {
+			compressLevel = zstd.SpeedBetterCompression
+		}
 		var compressed bytes.Buffer
-		compressor.ZstdCompress(bytes.NewReader(v), io.Writer(&compressed), zstd.WithEncoderLevel(zstd.SpeedBetterCompression))
+		compressor.ZstdCompress(bytes.NewReader(v), io.Writer(&compressed), zstd.WithEncoderLevel(compressLevel))
 		kvs[k] = compressed.String()
 	}
 

internal/querycoordv2/meta/target_manager_test.go

@@ -675,6 +675,53 @@ func (suite *TargetManagerSuite) TestGetTargetJSON() {
 	assert.Len(suite.T(), currentTarget[0].Segments, 2)
 }
 
+func BenchmarkTargetManager(b *testing.B) {
+	paramtable.Init()
+	config := GenerateEtcdConfig()
+	cli, _ := etcd.GetEtcdClient(
+		config.UseEmbedEtcd.GetAsBool(),
+		config.EtcdUseSSL.GetAsBool(),
+		config.Endpoints.GetAsStrings(),
+		config.EtcdTLSCert.GetValue(),
+		config.EtcdTLSKey.GetValue(),
+		config.EtcdTLSCACert.GetValue(),
+		config.EtcdTLSMinVersion.GetValue())
+
+	kv := etcdkv.NewEtcdKV(cli, config.MetaRootPath.GetValue())
+
+	catalog := querycoord.NewCatalog(kv)
+	idAllocator := RandomIncrementIDAllocator()
+	meta := NewMeta(idAllocator, catalog, session.NewNodeManager())
+	mgr := NewTargetManager(nil, meta)
+
+	segmentNum := 1000
+	segments := make(map[int64]*datapb.SegmentInfo)
+	for i := 0; i < segmentNum; i++ {
+		segments[int64(i)] = &datapb.SegmentInfo{
+			ID:            int64(i),
+			InsertChannel: "channel-1",
+		}
+	}
+
+	channels := map[string]*DmChannel{
+		"channel-1": {
+			VchannelInfo: &datapb.VchannelInfo{
+				CollectionID: int64(1),
+				ChannelName:  "channel-1",
+			},
+		},
+	}
+
+	collectionNum := 10000
+	for i := 0; i < collectionNum; i++ {
+		mgr.current.collectionTargetMap[int64(i)] = NewCollectionTarget(segments, channels, nil)
+	}
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		mgr.SaveCurrentTarget(context.TODO(), catalog)
+	}
+}
+
 func TestTargetManager(t *testing.T) {
 	suite.Run(t, new(TargetManagerSuite))
 }