refactor stats to not use internal data structures

- refactor to make it easier to split the api in the future
 - addition to check the existing test case and make sure it contains
   some expected output

Signed-off-by: Morgan Bauer <mbauer@us.ibm.com>

api/server/container.go

@@ -59,16 +59,6 @@ func (s *Server) getContainersStats(ctx context.Context, w http.ResponseWriter,
 	}
 
 	stream := boolValueOrDefault(r, "stream", true)
-
-	// If the container is not running and requires no stream, return an empty stats.
-	container, err := s.daemon.Get(vars["name"])
-	if err != nil {
-		return err
-	}
-	if !container.IsRunning() && !stream {
-		return writeJSON(w, http.StatusOK, &types.Stats{})
-	}
-
 	var out io.Writer
 	if !stream {
 		w.Header().Set("Content-Type", "application/json")
@@ -90,7 +80,7 @@ func (s *Server) getContainersStats(ctx context.Context, w http.ResponseWriter,
 		Version:   version,
 	}
 
-	return s.daemon.ContainerStats(container, config)
+	return s.daemon.ContainerStats(vars["name"], config)
 }
 
 func (s *Server) getContainersLogs(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error {

daemon/stats.go

@@ -22,7 +22,18 @@ type ContainerStatsConfig struct {
 
 // ContainerStats writes information about the container to the stream
 // given in the config object.
-func (daemon *Daemon) ContainerStats(container *Container, config *ContainerStatsConfig) error {
+func (daemon *Daemon) ContainerStats(prefixOrName string, config *ContainerStatsConfig) error {
+
+	container, err := daemon.Get(prefixOrName)
+	if err != nil {
+		return err
+	}
+
+	// If the container is not running and requires no stream, return an empty stats.
+	if !container.IsRunning() && !config.Stream {
+		return json.NewEncoder(config.OutStream).Encode(&types.Stats{})
+	}
+
 	updates, err := daemon.subscribeToContainerStats(container)
 	if err != nil {
 		return err

integration-cli/docker_cli_stats_test.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"bytes"
 	"os/exec"
 	"strings"
 	"time"
@@ -15,18 +16,28 @@ func (s *DockerSuite) TestCliStatsNoStream(c *check.C) {
 	c.Assert(waitRun(id), check.IsNil)
 
 	statsCmd := exec.Command(dockerBinary, "stats", "--no-stream", id)
-	chErr := make(chan error)
+	type output struct {
+		out []byte
+		err error
+	}
+
+	ch := make(chan output)
 	go func() {
-		chErr <- statsCmd.Run()
+		out, err := statsCmd.Output()
+		ch <- output{out, err}
 	}()
 
 	select {
-	case err := <-chErr:
+	case outerr := <-ch:
-		if err != nil {
+		if outerr.err != nil {
-			c.Fatalf("Error running stats: %v", err)
+			c.Fatalf("Error running stats: %v", outerr.err)
+		}
+		if !bytes.Contains(outerr.out, []byte(id)) {
+			c.Fatalf("running container wasn't present in output")
 		}
 	case <-time.After(3 * time.Second):
 		statsCmd.Process.Kill()
 		c.Fatalf("stats did not return immediately when not streaming")
 	}
+
 }