generate systemd: create pod template

Create a new template for generating a pod unit file. Eventually, this
allows for treating and extending pod and container generation
seprately.

The `--new` flag now also works on pods.

Signed-off-by: Valentin Rothberg <rothberg@redhat.com>

1 files changed, 111 insertions, 78 deletions

diff --git a/pkg/systemd/generate/containers.go b/pkg/systemd/generate/containers.go
index f316d4452..dced1a3da 100644
--- a/pkg/systemd/generate/containers.go
+++ b/pkg/systemd/generate/containers.go
@@ -33,14 +33,13 @@ type containerInfo struct {
 	// PIDFile of the service. Required for forking services. Must point to the
 	// PID of the associated conmon process.
 	PIDFile string
+	// ContainerIDFile to be used in the unit.
+	ContainerIDFile string
 	// GenerateTimestamp, if set the generated unit file has a time stamp.
 	GenerateTimestamp bool
 	// BoundToServices are the services this service binds to.  Note that this
 	// service runs after them.
 	BoundToServices []string
-	// RequiredServices are services this service requires. Note that this
-	// service runs before them.
-	RequiredServices []string
 	// PodmanVersion for the header. Will be set internally. Will be auto-filled
 	// if left empty.
 	PodmanVersion string
@@ -49,16 +48,23 @@ type containerInfo struct {
 	Executable string
 	// TimeStamp at the time of creating the unit file. Will be set internally.
 	TimeStamp string
-	// New controls if a new container is created or if an existing one is started.
-	New bool
 	// CreateCommand is the full command plus arguments of the process the
 	// container has been created with.
 	CreateCommand []string
-	// RunCommand is a post-processed variant of CreateCommand and used for
-	// the ExecStart field in generic unit files.
-	RunCommand string
 	// EnvVariable is generate.EnvVariable and must not be set.
 	EnvVariable string
+	// ExecStartPre of the unit.
+	ExecStartPre string
+	// ExecStart of the unit.
+	ExecStart string
+	// ExecStop of the unit.
+	ExecStop string
+	// ExecStopPost of the unit.
+	ExecStopPost string
+
+	// If not nil, the container is part of the pod.  We can use the
+	// podInfo to extract the relevant data.
+	pod *podInfo
 }
 
 const containerTemplate = headerTemplate + `
@@ -68,25 +74,19 @@ RefuseManualStop=yes
 BindsTo={{- range $index, $value := .BoundToServices -}}{{if $index}} {{end}}{{ $value }}.service{{end}}
 After={{- range $index, $value := .BoundToServices -}}{{if $index}} {{end}}{{ $value }}.service{{end}}
 {{- end}}
-{{- if .RequiredServices}}
-Requires={{- range $index, $value := .RequiredServices -}}{{if $index}} {{end}}{{ $value }}.service{{end}}
-Before={{- range $index, $value := .RequiredServices -}}{{if $index}} {{end}}{{ $value }}.service{{end}}
-{{- end}}
 
 [Service]
 Environment={{.EnvVariable}}=%n
 Restart={{.RestartPolicy}}
-{{- if .New}}
-ExecStartPre=/usr/bin/rm -f %t/%n-pid %t/%n-ctr-id
-ExecStart={{.RunCommand}}
-ExecStop={{.Executable}} stop --ignore --cidfile %t/%n-ctr-id {{if (ge .StopTimeout 0)}}-t {{.StopTimeout}}{{end}}
-ExecStopPost={{.Executable}} rm --ignore -f --cidfile %t/%n-ctr-id
-PIDFile=%t/%n-pid
-{{- else}}
-ExecStart={{.Executable}} start {{.ContainerNameOrID}}
-ExecStop={{.Executable}} stop {{if (ge .StopTimeout 0)}}-t {{.StopTimeout}}{{end}} {{.ContainerNameOrID}}
-PIDFile={{.PIDFile}}
+{{- if .ExecStartPre}}
+ExecStartPre={{.ExecStartPre}}
+{{- end}}
+ExecStart={{.ExecStart}}
+ExecStop={{.ExecStop}}
+{{- if .ExecStopPost}}
+ExecStopPost={{.ExecStopPost}}
 {{- end}}
+PIDFile={{.PIDFile}}
 KillMode=none
 Type=forking
 
@@ -101,11 +101,58 @@ func ContainerUnit(ctr *libpod.Container, options entities.GenerateSystemdOption
 	if err != nil {
 		return "", err
 	}
-	return createContainerSystemdUnit(info, options)
+	return executeContainerTemplate(info, options)
+}
+
+func generateContainerInfo(ctr *libpod.Container, options entities.GenerateSystemdOptions) (*containerInfo, error) {
+	timeout := ctr.StopTimeout()
+	if options.StopTimeout != nil {
+		timeout = *options.StopTimeout
+	}
+
+	config := ctr.Config()
+	conmonPidFile := config.ConmonPidFile
+	if conmonPidFile == "" {
+		return nil, errors.Errorf("conmon PID file path is empty, try to recreate the container with --conmon-pidfile flag")
+	}
+
+	createCommand := []string{}
+	if config.CreateCommand != nil {
+		createCommand = config.CreateCommand
+	} else if options.New {
+		return nil, errors.Errorf("cannot use --new on container %q: no create command found", ctr.ID())
+	}
+
+	nameOrID, serviceName := containerServiceName(ctr, options)
+
+	info := containerInfo{
+		ServiceName:       serviceName,
+		ContainerNameOrID: nameOrID,
+		RestartPolicy:     options.RestartPolicy,
+		PIDFile:           conmonPidFile,
+		StopTimeout:       timeout,
+		GenerateTimestamp: true,
+		CreateCommand:     createCommand,
+	}
+
+	return &info, nil
+}
+
+// containerServiceName returns the nameOrID and the service name of the
+// container.
+func containerServiceName(ctr *libpod.Container, options entities.GenerateSystemdOptions) (string, string) {
+	nameOrID := ctr.ID()
+	if options.Name {
+		nameOrID = ctr.Name()
+	}
+	serviceName := fmt.Sprintf("%s%s%s", options.ContainerPrefix, options.Separator, nameOrID)
+	return nameOrID, serviceName
 }
 
-// createContainerSystemdUnit creates a systemd unit file for a container.
-func createContainerSystemdUnit(info *containerInfo, options entities.GenerateSystemdOptions) (string, error) {
+// executeContainerTemplate executes the container template on the specified
+// containerInfo.  Note that the containerInfo is also post processed and
+// completed, which allows for an easier unit testing.
+func executeContainerTemplate(info *containerInfo, options entities.GenerateSystemdOptions) (string, error) {
 	if err := validateRestartPolicy(info.RestartPolicy); err != nil {
 		return "", err
 	}
@@ -121,6 +168,8 @@ func createContainerSystemdUnit(info *containerInfo, options entities.GenerateSy
 	}
 
 	info.EnvVariable = EnvVariable
+	info.ExecStart = "{{.Executable}} start {{.ContainerNameOrID}}"
+	info.ExecStop = "{{.Executable}} stop {{if (ge .StopTimeout 0)}}-t {{.StopTimeout}}{{end}} {{.ContainerNameOrID}}"
 
 	// Assemble the ExecStart command when creating a new container.
 	//
@@ -130,6 +179,8 @@ func createContainerSystemdUnit(info *containerInfo, options entities.GenerateSy
 	// invalid `info.CreateCommand`.  Hence, we're doing a best effort unit
 	// generation and don't try aiming at completeness.
 	if options.New {
+		info.PIDFile = "%t/" + info.ServiceName + ".pid"
+		info.ContainerIDFile = "%t/" + info.ServiceName + ".ctr-id"
 		// The create command must at least have three arguments:
 		// 	/usr/bin/podman run $IMAGE
 		index := 2
@@ -141,13 +192,20 @@ func createContainerSystemdUnit(info *containerInfo, options entities.GenerateSy
 		}
 		// We're hard-coding the first five arguments and append the
 		// CreateCommand with a stripped command and subcomand.
-		command := []string{
+		startCommand := []string{
 			info.Executable,
 			"run",
-			"--conmon-pidfile", "%t/%n-pid",
-			"--cidfile", "%t/%n-ctr-id",
+			"--conmon-pidfile", "{{.PIDFile}}",
+			"--cidfile", "{{.ContainerIDFile}}",
 			"--cgroups=no-conmon",
 		}
+		// If the container is in a pod, make sure that the
+		// --pod-id-file is set correctly.
+		if info.pod != nil {
+			podFlags := []string{"--pod-id-file", info.pod.PodIDFile}
+			startCommand = append(startCommand, podFlags...)
+			info.CreateCommand = filterPodFlags(info.CreateCommand)
+		}
 
 		// Enforce detaching
 		//
@@ -165,12 +223,14 @@ func createContainerSystemdUnit(info *containerInfo, options entities.GenerateSy
 			}
 		}
 		if !hasDetachParam {
-			command = append(command, "-d")
+			startCommand = append(startCommand, "-d")
 		}
+		startCommand = append(startCommand, info.CreateCommand[index:]...)
 
-		command = append(command, info.CreateCommand[index:]...)
-		info.RunCommand = strings.Join(command, " ")
-		info.New = true
+		info.ExecStartPre = "/usr/bin/rm -f {{.PIDFile}} {{.ContainerIDFile}}"
+		info.ExecStart = strings.Join(startCommand, " ")
+		info.ExecStop = "{{.Executable}} stop --ignore --cidfile {{.ContainerIDFile}} {{if (ge .StopTimeout 0)}}-t {{.StopTimeout}}{{end}}"
+		info.ExecStopPost = "{{.Executable}} rm --ignore -f --cidfile {{.ContainerIDFile}}"
 	}
 
 	if info.PodmanVersion == "" {
@@ -181,11 +241,17 @@ func createContainerSystemdUnit(info *containerInfo, options entities.GenerateSy
 	}
 
 	// Sort the slices to assure a deterministic output.
-	sort.Strings(info.RequiredServices)
 	sort.Strings(info.BoundToServices)
 
 	// Generate the template and compile it.
-	templ, err := template.New("systemd_service_file").Parse(containerTemplate)
+	//
+	// Note that we need a two-step generation process to allow for fields
+	// embedding other fields.  This way we can replace `A -> B -> C` and
+	// make the code easier to maintain at the cost of a slightly slower
+	// generation.  That's especially needed for embedding the PID and ID
+	// files in other fields which will eventually get replaced in the 2nd
+	// template execution.
+	templ, err := template.New("container_template").Parse(containerTemplate)
 	if err != nil {
 		return "", errors.Wrap(err, "error parsing systemd service template")
 	}
@@ -195,6 +261,17 @@ func createContainerSystemdUnit(info *containerInfo, options entities.GenerateSy
 		return "", err
 	}
 
+	// Now parse the generated template (i.e., buf) and execute it.
+	templ, err = template.New("container_template").Parse(buf.String())
+	if err != nil {
+		return "", errors.Wrap(err, "error parsing systemd service template")
+	}
+
+	buf = bytes.Buffer{}
+	if err := templ.Execute(&buf, info); err != nil {
+		return "", err
+	}
+
 	if !options.Files {
 		return buf.String(), nil
 	}
@@ -210,47 +287,3 @@ func createContainerSystemdUnit(info *containerInfo, options entities.GenerateSy
 	}
 	return path, nil
 }
-
-func generateContainerInfo(ctr *libpod.Container, options entities.GenerateSystemdOptions) (*containerInfo, error) {
-	timeout := ctr.StopTimeout()
-	if options.StopTimeout != nil {
-		timeout = *options.StopTimeout
-	}
-
-	config := ctr.Config()
-	conmonPidFile := config.ConmonPidFile
-	if conmonPidFile == "" {
-		return nil, errors.Errorf("conmon PID file path is empty, try to recreate the container with --conmon-pidfile flag")
-	}
-
-	createCommand := []string{}
-	if config.CreateCommand != nil {
-		createCommand = config.CreateCommand
-	} else if options.New {
-		return nil, errors.Errorf("cannot use --new on container %q: no create command found", ctr.ID())
-	}
-
-	nameOrID, serviceName := containerServiceName(ctr, options)
-
-	info := containerInfo{
-		ServiceName:       serviceName,
-		ContainerNameOrID: nameOrID,
-		RestartPolicy:     options.RestartPolicy,
-		PIDFile:           conmonPidFile,
-		StopTimeout:       timeout,
-		GenerateTimestamp: true,
-		CreateCommand:     createCommand,
-	}
-	return &info, nil
-}
-
-// containerServiceName returns the nameOrID and the service name of the
-// container.
-func containerServiceName(ctr *libpod.Container, options entities.GenerateSystemdOptions) (string, string) {
-	nameOrID := ctr.ID()
-	if options.Name {
-		nameOrID = ctr.Name()
-	}
-	serviceName := fmt.Sprintf("%s%s%s", options.ContainerPrefix, options.Separator, nameOrID)
-	return nameOrID, serviceName
-}