fix: Reduce task slot for standalone to 1/4 of normal datanode (#42808)

issue: #42129

---------

Signed-off-by: Cai Zhang <cai.zhang@zilliz.com>

internal/datanode/index/util.go

@@ -98,7 +98,7 @@ func CalculateNodeSlots() int64 {
 
 	totalSlot := max(slot, 1) * paramtable.Get().DataNodeCfg.WorkerSlotUnit.GetAsInt64() * paramtable.Get().DataNodeCfg.BuildParallel.GetAsInt64()
 	if paramtable.GetRole() == typeutil.StandaloneRole {
-		totalSlot = max(totalSlot/2, 1)
+		totalSlot = max(int64(float64(totalSlot)*paramtable.Get().DataNodeCfg.StandaloneSlotRatio.GetAsFloat()), 1)
 	}
 	return totalSlot
 }

pkg/util/paramtable/component_param.go

@@ -5191,7 +5191,8 @@ type dataNodeConfig struct {
 	// index services config
 	BuildParallel ParamItem `refreshable:"false"`
 
-	WorkerSlotUnit ParamItem `refreshable:"true"`
+	WorkerSlotUnit      ParamItem `refreshable:"true"`
+	StandaloneSlotRatio ParamItem `refreshable:"false"`
 }
 
 func (p *dataNodeConfig) init(base *BaseTable) {
@@ -5618,6 +5619,14 @@ if this parameter <= 0, will set it as 10`,
 		Doc:          "Indicates how many slots each worker occupies per 2c8g",
 	}
 	p.WorkerSlotUnit.Init(base.mgr)
+
+	p.StandaloneSlotRatio = ParamItem{
+		Key:          "dataNode.standaloneSlotFactor",
+		Version:      "2.5.14",
+		DefaultValue: "0.25",
+		Doc:          "Offline task slot ratio in standalone mode",
+	}
+	p.StandaloneSlotRatio.Init(base.mgr)
 }
 
 type streamingConfig struct {

pkg/util/paramtable/component_param_test.go

@@ -625,6 +625,8 @@ func TestComponentParam(t *testing.T) {
 		assert.Equal(t, int64(2), Params.ClusteringCompactionWorkerPoolSize.GetAsInt64())
 
 		assert.Equal(t, 2, Params.BloomFilterApplyParallelFactor.GetAsInt())
+		assert.Equal(t, 16, Params.WorkerSlotUnit.GetAsInt())
+		assert.Equal(t, 0.25, Params.StandaloneSlotRatio.GetAsFloat())
 	})
 
 	t.Run("test streamingConfig", func(t *testing.T) {