cli/command/container: use RWMutex for stats to allow concurrent reads

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

cli/command/container/formatter_stats.go

@@ -43,7 +43,7 @@ type StatsEntry struct {
 
 // Stats represents an entity to store containers statistics synchronously
 type Stats struct {
-	mutex sync.Mutex
+	mutex sync.RWMutex
 	StatsEntry
 	err error
 }
@@ -51,8 +51,8 @@ type Stats struct {
 // GetError returns the container statistics error.
 // This is used to determine whether the statistics are valid or not
 func (cs *Stats) GetError() error {
-	cs.mutex.Lock()
+	cs.mutex.RLock()
-	defer cs.mutex.Unlock()
+	defer cs.mutex.RUnlock()
 	return cs.err
 }
 
@@ -94,8 +94,8 @@ func (cs *Stats) SetStatistics(s StatsEntry) {
 
 // GetStatistics returns container statistics with other meta data such as the container name
 func (cs *Stats) GetStatistics() StatsEntry {
-	cs.mutex.Lock()
+	cs.mutex.RLock()
-	defer cs.mutex.Unlock()
+	defer cs.mutex.RUnlock()
 	return cs.StatsEntry
 }
 

cli/command/container/stats.go

@@ -184,13 +184,13 @@ func runStats(dockerCli command.Cli, opts *statsOptions) error {
 		waitFirst.Wait()
 
 		var errs []string
-		cStats.mu.Lock()
+		cStats.mu.RLock()
 		for _, c := range cStats.cs {
 			if err := c.GetError(); err != nil {
 				errs = append(errs, err.Error())
 			}
 		}
-		cStats.mu.Unlock()
+		cStats.mu.RUnlock()
 		if len(errs) > 0 {
 			return errors.New(strings.Join(errs, "\n"))
 		}
@@ -221,11 +221,11 @@ func runStats(dockerCli command.Cli, opts *statsOptions) error {
 	for range ticker.C {
 		cleanScreen()
 		ccstats := []StatsEntry{}
-		cStats.mu.Lock()
+		cStats.mu.RLock()
 		for _, c := range cStats.cs {
 			ccstats = append(ccstats, c.GetStatistics())
 		}
-		cStats.mu.Unlock()
+		cStats.mu.RUnlock()
 		if err = statsFormatWrite(statsCtx, ccstats, daemonOSType, !opts.noTrunc); err != nil {
 			break
 		}

cli/command/container/stats_helpers.go

@@ -14,7 +14,7 @@ import (
 )
 
 type stats struct {
-	mu sync.Mutex
+	mu sync.RWMutex
 	cs []*Stats
 }