diff --git a/internal/datacoord/cluster_store.go b/internal/datacoord/cluster_store.go
index 76c9defe7b3cdbaf0119221c9915451c7ae20cbb..6519f203c9bdac6a24f7830db66efbdb755d43fc 100644
--- a/internal/datacoord/cluster_store.go
+++ b/internal/datacoord/cluster_store.go
@@ -20,6 +20,7 @@ import (
 	"github.com/milvus-io/milvus/internal/types"
 )
 
+// ClusterStore is the interface stores DataNodes information
 type ClusterStore interface {
 	GetNodes() []*NodeInfo
 	SetNode(nodeID UniqueID, node *NodeInfo)
@@ -29,6 +30,8 @@ type ClusterStore interface {
 	SetWatched(nodeID UniqueID, channelsName []string)
 }
 
+// NodeInfo wrapper struct for storing DataNode information
+// and related controlling struct
 type NodeInfo struct {
 	Info    *datapb.DataNodeInfo
 	eventCh chan *NodeEvent
@@ -37,13 +40,16 @@ type NodeInfo struct {
 	cancel  context.CancelFunc
 }
 
+// eventChBuffer magic number for channel buffer size in NodeInfo
 const eventChBuffer = 1024
 
+// NodeEvent data node event struct
 type NodeEvent struct {
 	Type NodeEventType
 	Req  interface{}
 }
 
+// NewNodeInfo helper function to create a NodeInfo from provided datapb.DataNodeInfo
 func NewNodeInfo(ctx context.Context, info *datapb.DataNodeInfo) *NodeInfo {
 	ctx, cancel := context.WithCancel(ctx)
 	return &NodeInfo{
@@ -54,6 +60,8 @@ func NewNodeInfo(ctx context.Context, info *datapb.DataNodeInfo) *NodeInfo {
 	}
 }
 
+// ShadowClone shadow clones a NodeInfo
+// note that info, eventCh, etc is not created again
 func (n *NodeInfo) ShadowClone(opts ...NodeOpt) *NodeInfo {
 	cloned := &NodeInfo{
 		Info:    n.Info,
@@ -68,6 +76,9 @@ func (n *NodeInfo) ShadowClone(opts ...NodeOpt) *NodeInfo {
 	return cloned
 }
 
+// Clone "deep" clone a NodeInfo
+// note that ONLY `info` field is deep copied
+// parameter opts is applied in sequence to clone NodeInfo
 func (n *NodeInfo) Clone(opts ...NodeOpt) *NodeInfo {
 	info := proto.Clone(n.Info).(*datapb.DataNodeInfo)
 	cloned := &NodeInfo{
@@ -83,14 +94,17 @@ func (n *NodeInfo) Clone(opts ...NodeOpt) *NodeInfo {
 	return cloned
 }
 
+// GetEventChannel returns event channel
 func (n *NodeInfo) GetEventChannel() chan *NodeEvent {
 	return n.eventCh
 }
 
+// GetClient returns client
 func (n *NodeInfo) GetClient() types.DataNode {
 	return n.client
 }
 
+// Dispose stops the data node client and calls cancel
 func (n *NodeInfo) Dispose() {
 	defer n.cancel()
 	if n.client != nil {
@@ -98,10 +112,14 @@ func (n *NodeInfo) Dispose() {
 	}
 }
 
+// NodesInfo wraps a map UniqueID -> NodeInfo
+// implements ClusterStore interface
+// not lock related field is required so all operations shall be protected outside
 type NodesInfo struct {
 	nodes map[UniqueID]*NodeInfo
 }
 
+// NewNodesInfo helper function creates a NodesInfo
 func NewNodesInfo() *NodesInfo {
 	c := &NodesInfo{
 		nodes: make(map[UniqueID]*NodeInfo),
@@ -109,6 +127,7 @@ func NewNodesInfo() *NodesInfo {
 	return c
 }
 
+// GetNodes returns nodes list in NodesInfo
 func (c *NodesInfo) GetNodes() []*NodeInfo {
 	nodes := make([]*NodeInfo, 0, len(c.nodes))
 	for _, node := range c.nodes {
@@ -117,18 +136,22 @@ func (c *NodesInfo) GetNodes() []*NodeInfo {
 	return nodes
 }
 
+// SetNode sets a NodeInfo with provided UniqueID
 func (c *NodesInfo) SetNode(nodeID UniqueID, node *NodeInfo) {
 	c.nodes[nodeID] = node
 	metrics.DataCoordDataNodeList.WithLabelValues("online").Inc()
 	metrics.DataCoordDataNodeList.WithLabelValues("offline").Dec()
 }
 
+// DeleteNode deletes a NodeInfo with provided UniqueID
 func (c *NodesInfo) DeleteNode(nodeID UniqueID) {
 	delete(c.nodes, nodeID)
 	metrics.DataCoordDataNodeList.WithLabelValues("online").Dec()
 	metrics.DataCoordDataNodeList.WithLabelValues("offline").Inc()
 }
 
+// GetNode get NodeInfo binding to the specified UniqueID
+// returns nil if no Info is found
 func (c *NodesInfo) GetNode(nodeID UniqueID) *NodeInfo {
 	node, ok := c.nodes[nodeID]
 	if !ok {
@@ -137,20 +160,26 @@ func (c *NodesInfo) GetNode(nodeID UniqueID) *NodeInfo {
 	return node
 }
 
+// SetClient set DataNode client to specified UniqueID
+// do nothing if no Info is found
 func (c *NodesInfo) SetClient(nodeID UniqueID, client types.DataNode) {
 	if node, ok := c.nodes[nodeID]; ok {
 		c.nodes[nodeID] = node.ShadowClone(SetClient(client))
 	}
 }
 
+// SetWatched set specified channels watch state from Uncomplete to Complete
+// do nothing if no Info is found
 func (c *NodesInfo) SetWatched(nodeID UniqueID, channelsName []string) {
 	if node, ok := c.nodes[nodeID]; ok {
 		c.nodes[nodeID] = node.Clone(SetWatched(channelsName))
 	}
 }
 
+// NodeOpt helper functions updating NodeInfo properties
 type NodeOpt func(n *NodeInfo)
 
+// SetWatched returns a NodeOpt updating specified channels watch states from Uncomplete to Complete
 func SetWatched(channelsName []string) NodeOpt {
 	return func(n *NodeInfo) {
 		channelsMap := make(map[string]struct{})
@@ -169,18 +198,21 @@ func SetWatched(channelsName []string) NodeOpt {
 	}
 }
 
+// SetClient returns NodeOpt update DataNode client
 func SetClient(client types.DataNode) NodeOpt {
 	return func(n *NodeInfo) {
 		n.client = client
 	}
 }
 
+// AddChannels returns NodeOpt adding specified channels to assigned list
 func AddChannels(channels []*datapb.ChannelStatus) NodeOpt {
 	return func(n *NodeInfo) {
 		n.Info.Channels = append(n.Info.Channels, channels...)
 	}
 }
 
+// SetChannels returns NodeOpt updating assigned channels
 func SetChannels(channels []*datapb.ChannelStatus) NodeOpt {
 	return func(n *NodeInfo) {
 		n.Info.Channels = channels