generate systemd: refactor

Refactor the systemd-unit generation code and move all the logic into
`pkg/systemd/generate`.  The code was already hard to maintain but I
found it impossible to wire the `--new` logic for pods in all the chaos.

The code refactoring in this commit will make maintaining the code
easier and should make it easier to extend as well.  Further changes and
refactorings may still be needed but they will easier.

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

1 files changed, 130 insertions, 0 deletions

diff --git a/pkg/systemd/generate/pods.go b/pkg/systemd/generate/pods.go
new file mode 100644
index 000000000..16f324f78
--- /dev/null
+++ b/pkg/systemd/generate/pods.go
@@ -0,0 +1,130 @@
+package generate
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/containers/libpod/libpod"
+	"github.com/containers/libpod/pkg/domain/entities"
+	"github.com/pkg/errors"
+)
+
+// PodUnits generates systemd units for the specified pod and its containers.
+// Based on the options, the return value might be the content of all units or
+// the files they been written to.
+func PodUnits(pod *libpod.Pod, options entities.GenerateSystemdOptions) (string, error) {
+	if options.New {
+		return "", errors.New("--new is not supported for pods")
+	}
+
+	// Error out if the pod has no infra container, which we require to be the
+	// main service.
+	if !pod.HasInfraContainer() {
+		return "", fmt.Errorf("error generating systemd unit files: Pod %q has no infra container", pod.Name())
+	}
+
+	podInfo, err := generatePodInfo(pod, options)
+	if err != nil {
+		return "", err
+	}
+
+	infraID, err := pod.InfraContainerID()
+	if err != nil {
+		return "", err
+	}
+
+	// Compute the container-dependency graph for the Pod.
+	containers, err := pod.AllContainers()
+	if err != nil {
+		return "", err
+	}
+	if len(containers) == 0 {
+		return "", fmt.Errorf("error generating systemd unit files: Pod %q has no containers", pod.Name())
+	}
+	graph, err := libpod.BuildContainerGraph(containers)
+	if err != nil {
+		return "", err
+	}
+
+	// Traverse the dependency graph and create systemdgen.containerInfo's for
+	// each container.
+	containerInfos := []*containerInfo{podInfo}
+	for ctr, dependencies := range graph.DependencyMap() {
+		// Skip the infra container as we already generated it.
+		if ctr.ID() == infraID {
+			continue
+		}
+		ctrInfo, err := generateContainerInfo(ctr, options)
+		if err != nil {
+			return "", err
+		}
+		// Now add the container's dependencies and at the container as a
+		// required service of the infra container.
+		for _, dep := range dependencies {
+			if dep.ID() == infraID {
+				ctrInfo.BoundToServices = append(ctrInfo.BoundToServices, podInfo.ServiceName)
+			} else {
+				_, serviceName := containerServiceName(dep, options)
+				ctrInfo.BoundToServices = append(ctrInfo.BoundToServices, serviceName)
+			}
+		}
+		podInfo.RequiredServices = append(podInfo.RequiredServices, ctrInfo.ServiceName)
+		containerInfos = append(containerInfos, ctrInfo)
+	}
+
+	// Now generate the systemd service for all containers.
+	builder := strings.Builder{}
+	for i, info := range containerInfos {
+		if i > 0 {
+			builder.WriteByte('\n')
+		}
+		out, err := createContainerSystemdUnit(info, options)
+		if err != nil {
+			return "", err
+		}
+		builder.WriteString(out)
+	}
+
+	return builder.String(), nil
+}
+
+func generatePodInfo(pod *libpod.Pod, options entities.GenerateSystemdOptions) (*containerInfo, error) {
+	// Generate a systemdgen.containerInfo for the infra container. This
+	// containerInfo acts as the main service of the pod.
+	infraCtr, err := pod.InfraContainer()
+	if err != nil {
+		return nil, errors.Wrap(err, "could not find infra container")
+	}
+
+	timeout := infraCtr.StopTimeout()
+	if options.StopTimeout != nil {
+		timeout = *options.StopTimeout
+	}
+
+	config := infraCtr.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{}
+
+	nameOrID := pod.ID()
+	ctrNameOrID := infraCtr.ID()
+	if options.Name {
+		nameOrID = pod.Name()
+		ctrNameOrID = infraCtr.Name()
+	}
+	serviceName := fmt.Sprintf("%s%s%s", options.PodPrefix, options.Separator, nameOrID)
+
+	info := containerInfo{
+		ServiceName:       serviceName,
+		ContainerNameOrID: ctrNameOrID,
+		RestartPolicy:     options.RestartPolicy,
+		PIDFile:           conmonPidFile,
+		StopTimeout:       timeout,
+		GenerateTimestamp: true,
+		CreateCommand:     createCommand,
+	}
+	return &info, nil
+}