container-{create,run}: add `--pod-id-file`

Allow containers to join an existing pod via the `--pod-id-file` which
is already supported by a number of `podman-pod` subcommands.  Also add
tests to make sure it's working and to prevent future regressions.

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

4 files changed, 42 insertions, 0 deletions

diff --git a/cmd/podman/common/create.go b/cmd/podman/common/create.go
index 86cd51643..e79c5c20b 100644
--- a/cmd/podman/common/create.go
+++ b/cmd/podman/common/create.go
@@ -338,6 +338,11 @@ func GetCreateFlags(cf *ContainerCLIOpts) *pflag.FlagSet {
 		"pod", "",
 		"Run container in an existing pod",
 	)
+	createFlags.StringVar(
+		&cf.PodIDFile,
+		"pod-id-file", "",
+		"Read the pod ID from the file",
+	)
 	createFlags.BoolVar(
 		&cf.Privileged,
 		"privileged", false,
diff --git a/cmd/podman/common/create_opts.go b/cmd/podman/common/create_opts.go
index 4cba5daf7..98dc6744c 100644
--- a/cmd/podman/common/create_opts.go
+++ b/cmd/podman/common/create_opts.go
@@ -68,6 +68,7 @@ type ContainerCLIOpts struct {
 	PID               string
 	PIDsLimit         int64
 	Pod               string
+	PodIDFile         string
 	Privileged        bool
 	PublishAll        bool
 	Pull              string
diff --git a/cmd/podman/common/specgen.go b/cmd/podman/common/specgen.go
index 2286e67de..fee9d8c7b 100644
--- a/cmd/podman/common/specgen.go
+++ b/cmd/podman/common/specgen.go
@@ -254,6 +254,17 @@ func FillOutSpecGen(s *specgen.SpecGenerator, c *ContainerCLIOpts, args []string
 	s.PublishExposedPorts = c.PublishAll
 	s.Pod = c.Pod
 
+	if len(c.PodIDFile) > 0 {
+		if len(s.Pod) > 0 {
+			return errors.New("Cannot specify both --pod and --pod-id-file")
+		}
+		podID, err := ReadPodIDFile(c.PodIDFile)
+		if err != nil {
+			return err
+		}
+		s.Pod = podID
+	}
+
 	expose, err := createExpose(c.Expose)
 	if err != nil {
 		return err
diff --git a/cmd/podman/common/util.go b/cmd/podman/common/util.go
index a3626b4e4..422e241af 100644
--- a/cmd/podman/common/util.go
+++ b/cmd/podman/common/util.go
@@ -1,6 +1,7 @@
 package common
 
 import (
+	"io/ioutil"
 	"net"
 	"strconv"
 	"strings"
@@ -10,6 +11,30 @@ import (
 	"github.com/sirupsen/logrus"
 )
 
+// ReadPodIDFile reads the specified file and returns its content (i.e., first
+// line).
+func ReadPodIDFile(path string) (string, error) {
+	content, err := ioutil.ReadFile(path)
+	if err != nil {
+		return "", errors.Wrap(err, "error reading pod ID file")
+	}
+	return strings.Split(string(content), "\n")[0], nil
+}
+
+// ReadPodIDFiles reads the specified files and returns their content (i.e.,
+// first line).
+func ReadPodIDFiles(files []string) ([]string, error) {
+	ids := []string{}
+	for _, file := range files {
+		id, err := ReadPodIDFile(file)
+		if err != nil {
+			return nil, err
+		}
+		ids = append(ids, id)
+	}
+	return ids, nil
+}
+
 // createExpose parses user-provided exposed port definitions and converts them
 // into SpecGen format.
 // TODO: The SpecGen format should really handle ranges more sanely - we could