Merge pull request #17549 from donhcd/fixPre122Stats

fix pre-1.21 docker stats

daemon/stats.go

@@ -71,7 +71,8 @@ func (daemon *Daemon) ContainerStats(prefixOrName string, config *ContainerStats
 				return nil
 			}
 
-			statsJSON := getStatJSON(v)
+			var statsJSON interface{}
+			statsJSONPost120 := getStatJSON(v)
 			if config.Version.LessThan("1.21") {
 				var (
 					rxBytes   uint64
@@ -83,7 +84,7 @@ func (daemon *Daemon) ContainerStats(prefixOrName string, config *ContainerStats
 					txErrors  uint64
 					txDropped uint64
 				)
-				for _, v := range statsJSON.Networks {
+				for _, v := range statsJSONPost120.Networks {
 					rxBytes += v.RxBytes
 					rxPackets += v.RxPackets
 					rxErrors += v.RxErrors
@@ -93,8 +94,8 @@ func (daemon *Daemon) ContainerStats(prefixOrName string, config *ContainerStats
 					txErrors += v.TxErrors
 					txDropped += v.TxDropped
 				}
-				statsJSONPre121 := &v1p20.StatsJSON{
-					Stats: statsJSON.Stats,
+				statsJSON = &v1p20.StatsJSON{
+					Stats: statsJSONPost120.Stats,
 					Network: types.NetworkStats{
 						RxBytes:   rxBytes,
 						RxPackets: rxPackets,
@@ -106,20 +107,8 @@ func (daemon *Daemon) ContainerStats(prefixOrName string, config *ContainerStats
 						TxDropped: txDropped,
 					},
 				}
-
-				if !config.Stream && noStreamFirstFrame {
-					// prime the cpu stats so they aren't 0 in the final output
-					noStreamFirstFrame = false
-					continue
-				}
-
-				if err := enc.Encode(statsJSONPre121); err != nil {
-					return err
-				}
-
-				if !config.Stream {
-					return nil
-				}
+			} else {
+				statsJSON = statsJSONPost120
 			}
 
 			if !config.Stream && noStreamFirstFrame {