save start error into State.Error

when a container failed to start, saves the error message into State.Error so
that it can be retrieved when calling `docker inspect` instead of having to
look at the log

Docker-DCO-1.1-Signed-off-by: Daniel, Dao Quang Minh <dqminh89@gmail.com> (github: dqminh)

daemon/container.go

@@ -297,6 +297,8 @@ func (container *Container) Start() (err error) {
 	// setup has been cleaned up properly
 	defer func() {
 		if err != nil {
+			container.setError(err)
+			container.toDisk()
 			container.cleanup()
 		}
 	}()

daemon/state.go

@@ -15,6 +15,7 @@ type State struct {
 	Restarting bool
 	Pid        int
 	ExitCode   int
+	Error      string // contains last known error when starting the container
 	StartedAt  time.Time
 	FinishedAt time.Time
 	waitChan   chan struct{}
@@ -137,6 +138,7 @@ func (s *State) SetRunning(pid int) {
 }
 
 func (s *State) setRunning(pid int) {
+	s.Error = ""
 	s.Running = true
 	s.Paused = false
 	s.Restarting = false
@@ -179,6 +181,13 @@ func (s *State) SetRestarting(exitCode int) {
 	s.Unlock()
 }
 
+// setError sets the container's error state. This is useful when we want to
+// know the error that occurred when container transits to another state
+// when inspecting it
+func (s *State) setError(err error) {
+	s.Error = err.Error()
+}
+
 func (s *State) IsRestarting() bool {
 	s.Lock()
 	res := s.Restarting

integration-cli/docker_cli_start_test.go

@@ -68,3 +68,44 @@ func TestStartAttachCorrectExitCode(t *testing.T) {
 
 	logDone("start - correct exit code returned with -a")
 }
+
+func TestStartRecordError(t *testing.T) {
+	defer deleteAllContainers()
+
+	// when container runs successfully, we should not have state.Error
+	cmd(t, "run", "-d", "-p", "9999:9999", "--name", "test", "busybox", "top")
+	stateErr, err := inspectField("test", "State.Error")
+	if err != nil {
+		t.Fatalf("Failed to inspect %q state's error, got error %q", "test", err)
+	}
+	if stateErr != "" {
+		t.Fatalf("Expected to not have state error but got state.Error(%q)", stateErr)
+	}
+
+	// Expect this to fail and records error because of ports conflict
+	out, _, err := runCommandWithOutput(exec.Command(dockerBinary, "run", "-d", "--name", "test2", "-p", "9999:9999", "busybox", "top"))
+	if err == nil {
+		t.Fatalf("Expected error but got none, output %q", out)
+	}
+	stateErr, err = inspectField("test2", "State.Error")
+	if err != nil {
+		t.Fatalf("Failed to inspect %q state's error, got error %q", "test2", err)
+	}
+	expected := "port is already allocated"
+	if stateErr == "" || !strings.Contains(stateErr, expected) {
+		t.Fatalf("State.Error(%q) does not include %q", stateErr, expected)
+	}
+
+	// Expect the conflict to be resolved when we stop the initial container
+	cmd(t, "stop", "test")
+	cmd(t, "start", "test2")
+	stateErr, err = inspectField("test2", "State.Error")
+	if err != nil {
+		t.Fatalf("Failed to inspect %q state's error, got error %q", "test", err)
+	}
+	if stateErr != "" {
+		t.Fatalf("Expected to not have state error but got state.Error(%q)", stateErr)
+	}
+
+	logDone("start - set state error when start fails")
+}