From 2cba5053a8b4b7911094324a9823d32f2f0ff25f Mon Sep 17 00:00:00 2001
From: groot <yihua.mo@zilliz.com>
Date: Mon, 11 Oct 2021 19:00:46 +0800
Subject: [PATCH] Add comment for QueryCoordComponent (#9648)

Signed-off-by: yhmo <yihua.mo@zilliz.com>
---
 .../distributed/querycoord/service_test.go    |  6 +++--
 internal/querycoord/query_coord.go            | 15 +++++++++++--
 internal/types/types.go                       | 22 ++++++++++++++-----
 3 files changed, 34 insertions(+), 9 deletions(-)

diff --git a/internal/distributed/querycoord/service_test.go b/internal/distributed/querycoord/service_test.go
index 57b0614e63..b56d862a39 100644
--- a/internal/distributed/querycoord/service_test.go
+++ b/internal/distributed/querycoord/service_test.go
@@ -66,10 +66,12 @@ func (m *MockQueryCoord) Register() error {
 func (m *MockQueryCoord) UpdateStateCode(code internalpb.StateCode) {
 }
 
-func (m *MockQueryCoord) SetRootCoord(types.RootCoord) {
+func (m *MockQueryCoord) SetRootCoord(types.RootCoord) error {
+	return nil
 }
 
-func (m *MockQueryCoord) SetDataCoord(types.DataCoord) {
+func (m *MockQueryCoord) SetDataCoord(types.DataCoord) error {
+	return nil
 }
 
 func (m *MockQueryCoord) GetComponentStates(ctx context.Context) (*internalpb.ComponentStates, error) {
diff --git a/internal/querycoord/query_coord.go b/internal/querycoord/query_coord.go
index e4c1f093b4..9a0d65bd4e 100644
--- a/internal/querycoord/query_coord.go
+++ b/internal/querycoord/query_coord.go
@@ -13,6 +13,7 @@ package querycoord
 
 import (
 	"context"
+	"errors"
 	"math/rand"
 	"path/filepath"
 	"strconv"
@@ -194,13 +195,23 @@ func NewQueryCoord(ctx context.Context, factory msgstream.Factory) (*QueryCoord,
 }
 
 // SetRootCoord sets root coordinator's client
-func (qc *QueryCoord) SetRootCoord(rootCoord types.RootCoord) {
+func (qc *QueryCoord) SetRootCoord(rootCoord types.RootCoord) error {
+	if rootCoord == nil {
+		return errors.New("null root coordinator interface")
+	}
+
 	qc.rootCoordClient = rootCoord
+	return nil
 }
 
 // SetDataCoord sets data coordinator's client
-func (qc *QueryCoord) SetDataCoord(dataCoord types.DataCoord) {
+func (qc *QueryCoord) SetDataCoord(dataCoord types.DataCoord) error {
+	if dataCoord == nil {
+		return errors.New("null data coordinator interface")
+	}
+
 	qc.dataCoordClient = dataCoord
+	return nil
 }
 
 func (qc *QueryCoord) watchNodeLoop() {
diff --git a/internal/types/types.go b/internal/types/types.go
index c503dfbf58..0a9bf94c29 100644
--- a/internal/types/types.go
+++ b/internal/types/types.go
@@ -539,7 +539,7 @@ type QueryNodeComponent interface {
 
 	// UpdateStateCode updates state code for QueryNode
 	//  `stateCode` is current statement of this query node, indicating whether it's healthy.
-	UpdateStateCode(code internalpb.StateCode)
+	UpdateStateCode(stateCode internalpb.StateCode)
 
 	// SetRootCoord set RootCoord for QueryNode
 	// `rootCoord` is a client of root coordinator. Pass to segmentLoader.
@@ -583,12 +583,24 @@ type QueryCoordComponent interface {
 	QueryCoord
 
 	// UpdateStateCode updates state code for QueryCoord
-	// State includes: Initializing, Healthy and Abnormal
-	UpdateStateCode(internalpb.StateCode)
+	//  `stateCode` is current statement of this query coord, indicating whether it's healthy.
+	UpdateStateCode(stateCode internalpb.StateCode)
 
 	// SetDataCoord set DataCoord for QueryCoord
-	SetDataCoord(DataCoord)
+	// `dataCoord` is a client of data coordinator.
+	//
+	// Return a generic error in status:
+	//     If the dataCoord is nil.
+	// Return nil in status:
+	//     The dataCoord is not nil.
+	SetDataCoord(dataCoord DataCoord) error
 
 	// SetRootCoord set RootCoord for QueryCoord
-	SetRootCoord(RootCoord)
+	// `rootCoord` is a client of root coordinator.
+	//
+	// Return a generic error in status:
+	//     If the rootCoord is nil.
+	// Return nil in status:
+	//     The rootCoord is not nil.
+	SetRootCoord(rootCoord RootCoord) error
 }