auto updates

Add support to auto-update containers running in systemd units as
generated with `podman generate systemd --new`.

`podman auto-update` looks up containers with a specified
"io.containers.autoupdate" label (i.e., the auto-update policy).

If the label is present and set to "image", Podman reaches out to the
corresponding registry to check if the image has been updated.  We
consider an image to be updated if the digest in the local storage is
different than the one of the remote image.  If an image must be
updated, Podman pulls it down and restarts the container.  Note that the
restarting sequence relies on systemd.

At container-creation time, Podman looks up the "PODMAN_SYSTEMD_UNIT"
environment variables and stores it verbatim in the container's label.
This variable is now set by all systemd units generated by
`podman-generate-systemd` and is set to `%n` (i.e., the name of systemd
unit starting the container).  This data is then being used in the
auto-update sequence to instruct systemd (via DBUS) to restart the unit
and hence to restart the container.

Note that this implementation of auto-updates relies on systemd and
requires a fully-qualified image reference to be used to create the
container.  This enforcement is necessary to know which image to
actually check and pull.  If we used an image ID, we would not know
which image to check/pull anymore.

Fixes: #3575
Signed-off-by: Valentin Rothberg <rothberg@redhat.com>

9 files changed, 375 insertions, 2 deletions

diff --git a/pkg/adapter/autoupdate.go b/pkg/adapter/autoupdate.go
new file mode 100644
index 000000000..01f7a29c5
--- /dev/null
+++ b/pkg/adapter/autoupdate.go
@@ -0,0 +1,11 @@
+// +build !remoteclient
+
+package adapter
+
+import (
+	"github.com/containers/libpod/pkg/autoupdate"
+)
+
+func (r *LocalRuntime) AutoUpdate() ([]string, []error) {
+	return autoupdate.AutoUpdate(r.Runtime)
+}
diff --git a/pkg/adapter/autoupdate_remote.go b/pkg/adapter/autoupdate_remote.go
new file mode 100644
index 000000000..a2a82d0d4
--- /dev/null
+++ b/pkg/adapter/autoupdate_remote.go
@@ -0,0 +1,11 @@
+// +build remoteclient
+
+package adapter
+
+import (
+	"github.com/containers/libpod/libpod/define"
+)
+
+func (r *LocalRuntime) AutoUpdate() ([]string, []error) {
+	return nil, []error{define.ErrNotImplemented}
+}
diff --git a/pkg/autoupdate/autoupdate.go b/pkg/autoupdate/autoupdate.go
new file mode 100644
index 000000000..7c243eb00
--- /dev/null
+++ b/pkg/autoupdate/autoupdate.go
@@ -0,0 +1,280 @@
+package autoupdate
+
+import (
+	"context"
+	"os"
+	"sort"
+
+	"github.com/containers/image/v5/docker"
+	"github.com/containers/image/v5/docker/reference"
+	"github.com/containers/image/v5/manifest"
+	"github.com/containers/image/v5/transports/alltransports"
+	"github.com/containers/libpod/libpod"
+	"github.com/containers/libpod/libpod/define"
+	"github.com/containers/libpod/libpod/image"
+	"github.com/containers/libpod/pkg/systemd"
+	systemdGen "github.com/containers/libpod/pkg/systemd/generate"
+	"github.com/containers/libpod/pkg/util"
+	"github.com/pkg/errors"
+	"github.com/sirupsen/logrus"
+)
+
+// Label denotes the container/pod label key to specify auto-update policies in
+// container labels.
+const Label = "io.containers.autoupdate"
+
+// Policy represents an auto-update policy.
+type Policy string
+
+const (
+	// PolicyDefault is the default policy denoting no auto updates.
+	PolicyDefault Policy = "disabled"
+	// PolicyNewImage is the policy to update as soon as there's a new image found.
+	PolicyNewImage = "image"
+)
+
+// Map for easy lookups of supported policies.
+var supportedPolicies = map[string]Policy{
+	"":         PolicyDefault,
+	"disabled": PolicyDefault,
+	"image":    PolicyNewImage,
+}
+
+// LookupPolicy looksup the corresponding Policy for the specified
+// string. If none is found, an errors is returned including the list of
+// supported policies.
+//
+// Note that an empty string resolved to PolicyDefault.
+func LookupPolicy(s string) (Policy, error) {
+	policy, exists := supportedPolicies[s]
+	if exists {
+		return policy, nil
+	}
+
+	// Sort the keys first as maps are non-deterministic.
+	keys := []string{}
+	for k := range supportedPolicies {
+		if k != "" {
+			keys = append(keys, k)
+		}
+	}
+	sort.Strings(keys)
+
+	return "", errors.Errorf("invalid auto-update policy %q: valid policies are %+q", s, keys)
+}
+
+// ValidateImageReference checks if the specified imageName is a fully-qualified
+// image reference to the docker transport (without digest).  Such a reference
+// includes a domain, name and tag (e.g., quay.io/podman/stable:latest).  The
+// reference may also be prefixed with "docker://" explicitly indicating that
+// it's a reference to the docker transport.
+func ValidateImageReference(imageName string) error {
+	// Make sure the input image is a docker.
+	imageRef, err := alltransports.ParseImageName(imageName)
+	if err == nil && imageRef.Transport().Name() != docker.Transport.Name() {
+		return errors.Errorf("auto updates require the docker image transport but image is of transport %q", imageRef.Transport().Name())
+	} else if err != nil {
+		repo, err := reference.Parse(imageName)
+		if err != nil {
+			return errors.Wrap(err, "error enforcing fully-qualified docker transport reference for auto updates")
+		}
+		if _, ok := repo.(reference.NamedTagged); !ok {
+			return errors.Errorf("auto updates require fully-qualified image references (no tag): %q", imageName)
+		}
+		if _, ok := repo.(reference.Digested); ok {
+			return errors.Errorf("auto updates require fully-qualified image references without digest: %q", imageName)
+		}
+	}
+	return nil
+}
+
+// AutoUpdate looks up containers with a specified auto-update policy and acts
+// accordingly.  If the policy is set to PolicyNewImage, it checks if the image
+// on the remote registry is different than the local one. If the image digests
+// differ, it pulls the remote image and restarts the systemd unit running the
+// container.
+//
+// It returns a slice of successfully restarted systemd units and a slice of
+// errors encountered during auto update.
+func AutoUpdate(runtime *libpod.Runtime) ([]string, []error) {
+	// Create a map from `image ID -> []*Container`.
+	containerMap, errs := imageContainersMap(runtime)
+	if len(containerMap) == 0 {
+		return nil, errs
+	}
+
+	// Create a map from `image ID -> *image.Image` for image lookups.
+	imagesSlice, err := runtime.ImageRuntime().GetImages()
+	if err != nil {
+		return nil, []error{err}
+	}
+	imageMap := make(map[string]*image.Image)
+	for i := range imagesSlice {
+		imageMap[imagesSlice[i].ID()] = imagesSlice[i]
+	}
+
+	// Connect to DBUS.
+	conn, err := systemd.ConnectToDBUS()
+	if err != nil {
+		logrus.Errorf(err.Error())
+		return nil, []error{err}
+	}
+	defer conn.Close()
+
+	// Update images.
+	containersToRestart := []*libpod.Container{}
+	updatedRawImages := make(map[string]bool)
+	for imageID, containers := range containerMap {
+		image, exists := imageMap[imageID]
+		if !exists {
+			errs = append(errs, errors.Errorf("container image ID %q not found in local storage", imageID))
+			return nil, errs
+		}
+		// Now we have to check if the image of any containers must be updated.
+		// Note that the image ID is NOT enough for this check as a given image
+		// may have multiple tags.
+		for i, ctr := range containers {
+			rawImageName := ctr.RawImageName()
+			if rawImageName == "" {
+				errs = append(errs, errors.Errorf("error auto-updating container %q: raw-image name is empty", ctr.ID()))
+			}
+			needsUpdate, err := newerImageAvailable(runtime, image, rawImageName)
+			if err != nil {
+				errs = append(errs, errors.Wrapf(err, "error auto-updating container %q: image check for %q failed", ctr.ID(), rawImageName))
+				continue
+			}
+			if !needsUpdate {
+				continue
+			}
+			logrus.Infof("Auto-updating container %q using image %q", ctr.ID(), rawImageName)
+			if _, updated := updatedRawImages[rawImageName]; !updated {
+				_, err = updateImage(runtime, rawImageName)
+				if err != nil {
+					errs = append(errs, errors.Wrapf(err, "error auto-updating container %q: image update for %q failed", ctr.ID(), rawImageName))
+					continue
+				}
+				updatedRawImages[rawImageName] = true
+			}
+			containersToRestart = append(containersToRestart, containers[i])
+		}
+	}
+
+	// Restart containers.
+	updatedUnits := []string{}
+	for _, ctr := range containersToRestart {
+		labels := ctr.Labels()
+		unit, exists := labels[systemdGen.EnvVariable]
+		if !exists {
+			// Shouldn't happen but let's be sure of it.
+			errs = append(errs, errors.Errorf("error auto-updating container %q: no %s label found", ctr.ID(), systemdGen.EnvVariable))
+			continue
+		}
+		_, err := conn.RestartUnit(unit, "replace", nil)
+		if err != nil {
+			errs = append(errs, errors.Wrapf(err, "error auto-updating container %q: restarting systemd unit %q failed", ctr.ID(), unit))
+			continue
+		}
+		logrus.Infof("Successfully restarted systemd unit %q", unit)
+		updatedUnits = append(updatedUnits, unit)
+	}
+
+	return updatedUnits, errs
+}
+
+// imageContainersMap generates a map[image ID] -> [containers using the image]
+// of all containers with a valid auto-update policy.
+func imageContainersMap(runtime *libpod.Runtime) (map[string][]*libpod.Container, []error) {
+	allContainers, err := runtime.GetAllContainers()
+	if err != nil {
+		return nil, []error{err}
+	}
+
+	errors := []error{}
+	imageMap := make(map[string][]*libpod.Container)
+	for i, ctr := range allContainers {
+		state, err := ctr.State()
+		if err != nil {
+			errors = append(errors, err)
+			continue
+		}
+		// Only update running containers.
+		if state != define.ContainerStateRunning {
+			continue
+		}
+		// Only update containers with the specific label/policy set.
+		labels := ctr.Labels()
+		if value, exists := labels[Label]; exists {
+			policy, err := LookupPolicy(value)
+			if err != nil {
+				errors = append(errors, err)
+				continue
+			}
+			if policy != PolicyNewImage {
+				continue
+			}
+		}
+		// Now we know that `ctr` is configured for auto updates.
+		id, _ := ctr.Image()
+		imageMap[id] = append(imageMap[id], allContainers[i])
+	}
+
+	return imageMap, errors
+}
+
+// newerImageAvailable returns true if there corresponding image on the remote
+// registry is newer.
+func newerImageAvailable(runtime *libpod.Runtime, img *image.Image, origName string) (bool, error) {
+	remoteRef, err := docker.ParseReference("//" + origName)
+	if err != nil {
+		return false, err
+	}
+
+	remoteImg, err := remoteRef.NewImage(context.Background(), runtime.SystemContext())
+	if err != nil {
+		return false, err
+	}
+
+	rawManifest, _, err := remoteImg.Manifest(context.Background())
+	if err != nil {
+		return false, err
+	}
+
+	remoteDigest, err := manifest.Digest(rawManifest)
+	if err != nil {
+		return false, err
+	}
+
+	return img.Digest().String() != remoteDigest.String(), nil
+}
+
+// updateImage pulls the specified image.
+func updateImage(runtime *libpod.Runtime, name string) (*image.Image, error) {
+	sys := runtime.SystemContext()
+	registryOpts := image.DockerRegistryOptions{}
+	signaturePolicyPath := ""
+	authFilePath := ""
+
+	if sys != nil {
+		registryOpts.OSChoice = sys.OSChoice
+		registryOpts.ArchitectureChoice = sys.OSChoice
+		registryOpts.DockerCertPath = sys.DockerCertPath
+
+		signaturePolicyPath = sys.SignaturePolicyPath
+		authFilePath = sys.AuthFilePath
+	}
+
+	newImage, err := runtime.ImageRuntime().New(context.Background(),
+		docker.Transport.Name()+"://"+name,
+		signaturePolicyPath,
+		authFilePath,
+		os.Stderr,
+		&registryOpts,
+		image.SigningOptions{},
+		nil,
+		util.PullImageAlways,
+	)
+	if err != nil {
+		return nil, err
+	}
+	return newImage, nil
+}
diff --git a/pkg/autoupdate/autoupdate_test.go b/pkg/autoupdate/autoupdate_test.go
new file mode 100644
index 000000000..7a5da5bb0
--- /dev/null
+++ b/pkg/autoupdate/autoupdate_test.go
@@ -0,0 +1,50 @@
+package autoupdate
+
+import (
+	"testing"
+)
+
+func TestValidateImageReference(t *testing.T) {
+	tests := []struct {
+		input string
+		valid bool
+	}{
+		{ // Fully-qualified reference
+			input: "quay.io/foo/bar:tag",
+			valid: true,
+		},
+		{ // Fully-qualified reference in transport notation
+			input: "docker://quay.io/foo/bar:tag",
+			valid: true,
+		},
+		{ // Fully-qualified reference but with digest
+			input: "quay.io/foo/bar@sha256:c9b1b535fdd91a9855fb7f82348177e5f019329a58c53c47272962dd60f71fc9",
+			valid: false,
+		},
+		{ // Reference with missing tag
+			input: "quay.io/foo/bar",
+			valid: false,
+		},
+		{ // Short name
+			input: "alpine",
+			valid: false,
+		},
+		{ // Short name with repo
+			input: "library/alpine",
+			valid: false,
+		},
+		{ // Wrong transport
+			input: "docker-archive:/some/path.tar",
+			valid: false,
+		},
+	}
+
+	for _, test := range tests {
+		err := ValidateImageReference(test.input)
+		if test.valid && err != nil {
+			t.Fatalf("parsing %q should have succeeded: %v", test.input, err)
+		} else if !test.valid && err == nil {
+			t.Fatalf("parsing %q should have failed", test.input)
+		}
+	}
+}
diff --git a/pkg/spec/createconfig.go b/pkg/spec/createconfig.go
index 9b2255d61..12dfed8c3 100644
--- a/pkg/spec/createconfig.go
+++ b/pkg/spec/createconfig.go
@@ -144,6 +144,7 @@ type CreateConfig struct {
 	InitPath          string //init-path
 	Image             string
 	ImageID           string
+	RawImageName      string
 	BuiltinImgVolumes map[string]struct{} // volumes defined in the image config
 	ImageVolumeType   string              // how to handle the image volume, either bind, tmpfs, or ignore
 	Interactive       bool                //interactive
@@ -348,7 +349,7 @@ func (c *CreateConfig) getContainerCreateOptions(runtime *libpod.Runtime, pod *l
 	options = append(options, nsOpts...)
 
 	// Gather up the options for NewContainer which consist of With... funcs
-	options = append(options, libpod.WithRootFSFromImage(c.ImageID, c.Image))
+	options = append(options, libpod.WithRootFSFromImage(c.ImageID, c.Image, c.RawImageName))
 	options = append(options, libpod.WithConmonPidFile(c.ConmonPidFile))
 	options = append(options, libpod.WithLabels(c.Labels))
 	options = append(options, libpod.WithShmSize(c.Resources.ShmSize))
diff --git a/pkg/specgen/create.go b/pkg/specgen/create.go
index 99a99083b..aefbe7405 100644
--- a/pkg/specgen/create.go
+++ b/pkg/specgen/create.go
@@ -36,7 +36,7 @@ func (s *SpecGenerator) MakeContainer(rt *libpod.Runtime) (*libpod.Container, er
 		return nil, err
 	}
 
-	options = append(options, libpod.WithRootFSFromImage(newImage.ID(), s.Image))
+	options = append(options, libpod.WithRootFSFromImage(newImage.ID(), s.Image, s.RawImageName))
 
 	runtimeSpec, err := s.toOCISpec(rt, newImage)
 	if err != nil {
diff --git a/pkg/specgen/specgen.go b/pkg/specgen/specgen.go
index e1dfe4dc5..7a430652a 100644
--- a/pkg/specgen/specgen.go
+++ b/pkg/specgen/specgen.go
@@ -143,6 +143,10 @@ type ContainerStorageConfig struct {
 	// Conflicts with Rootfs.
 	// At least one of Image or Rootfs must be specified.
 	Image string `json:"image"`
+	// RawImageName is the unprocessed and not-normalized user-specified image
+	// name.  One use case for having this data at hand are auto-updates where
+	// the _exact_ user input is needed in order to look-up the correct image.
+	RawImageName string `json:"raw_image_name,omitempty"`
 	// Rootfs is the path to a directory that will be used as the
 	// container's root filesystem. No modification will be made to the
 	// directory, it will be directly mounted into the container as root.
diff --git a/pkg/systemd/generate/systemdgen.go b/pkg/systemd/generate/systemdgen.go
index 4cd7745c0..eb15d4927 100644
--- a/pkg/systemd/generate/systemdgen.go
+++ b/pkg/systemd/generate/systemdgen.go
@@ -16,6 +16,10 @@ import (
 	"github.com/sirupsen/logrus"
 )
 
+// EnvVariable "PODMAN_SYSTEMD_UNIT" is set in all generated systemd units and
+// is set to the unit's (unique) name.
+const EnvVariable = "PODMAN_SYSTEMD_UNIT"
+
 // ContainerInfo contains data required for generating a container's systemd
 // unit file.
 type ContainerInfo struct {
@@ -57,6 +61,8 @@ type ContainerInfo struct {
 	// 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
 }
 
 var restartPolicies = []string{"no", "on-success", "on-failure", "on-abnormal", "on-watchdog", "on-abort", "always"}
@@ -94,6 +100,7 @@ Before={{- range $index, $value := .RequiredServices -}}{{if $index}} {{end}}{{
 {{- end}}
 
 [Service]
+Environment={{.EnvVariable}}=%n
 Restart={{.RestartPolicy}}
 {{- if .New}}
 ExecStartPre=/usr/bin/rm -f %t/%n-pid %t/%n-cid
@@ -138,6 +145,8 @@ func CreateContainerSystemdUnit(info *ContainerInfo, opts Options) (string, erro
 		info.Executable = executable
 	}
 
+	info.EnvVariable = EnvVariable
+
 	// Assemble the ExecStart command when creating a new container.
 	//
 	// Note that we cannot catch all corner cases here such that users
diff --git a/pkg/systemd/generate/systemdgen_test.go b/pkg/systemd/generate/systemdgen_test.go
index bbdccdcf8..3269405a6 100644
--- a/pkg/systemd/generate/systemdgen_test.go
+++ b/pkg/systemd/generate/systemdgen_test.go
@@ -44,6 +44,7 @@ Wants=network.target
 After=network-online.target
 
 [Service]
+Environment=PODMAN_SYSTEMD_UNIT=%n
 Restart=always
 ExecStart=/usr/bin/podman start 639c53578af4d84b8800b4635fa4e680ee80fd67e0e6a2d4eea48d1e3230f401
 ExecStop=/usr/bin/podman stop -t 10 639c53578af4d84b8800b4635fa4e680ee80fd67e0e6a2d4eea48d1e3230f401
@@ -64,6 +65,7 @@ Wants=network.target
 After=network-online.target
 
 [Service]
+Environment=PODMAN_SYSTEMD_UNIT=%n
 Restart=always
 ExecStart=/usr/bin/podman start foobar
 ExecStop=/usr/bin/podman stop -t 10 foobar
@@ -88,6 +90,7 @@ BindsTo=a.service b.service c.service pod.service
 After=a.service b.service c.service pod.service
 
 [Service]
+Environment=PODMAN_SYSTEMD_UNIT=%n
 Restart=always
 ExecStart=/usr/bin/podman start foobar
 ExecStop=/usr/bin/podman stop -t 10 foobar
@@ -110,6 +113,7 @@ Requires=container-1.service container-2.service
 Before=container-1.service container-2.service
 
 [Service]
+Environment=PODMAN_SYSTEMD_UNIT=%n
 Restart=always
 ExecStart=/usr/bin/podman start jadda-jadda-infra
 ExecStop=/usr/bin/podman stop -t 10 jadda-jadda-infra
@@ -130,6 +134,7 @@ Wants=network.target
 After=network-online.target
 
 [Service]
+Environment=PODMAN_SYSTEMD_UNIT=%n
 Restart=always
 ExecStartPre=/usr/bin/rm -f %t/%n-pid %t/%n-cid
 ExecStart=/usr/bin/podman run --conmon-pidfile %t/%n-pid --cidfile %t/%n-cid --cgroups=no-conmon -d --name jadda-jadda --hostname hello-world awesome-image:latest command arg1 ... argN
@@ -152,6 +157,7 @@ Wants=network.target
 After=network-online.target
 
 [Service]
+Environment=PODMAN_SYSTEMD_UNIT=%n
 Restart=always
 ExecStartPre=/usr/bin/rm -f %t/%n-pid %t/%n-cid
 ExecStart=/usr/bin/podman run --conmon-pidfile %t/%n-pid --cidfile %t/%n-cid --cgroups=no-conmon --detach --name jadda-jadda --hostname hello-world awesome-image:latest command arg1 ... argN
@@ -174,6 +180,7 @@ Wants=network.target
 After=network-online.target
 
 [Service]
+Environment=PODMAN_SYSTEMD_UNIT=%n
 Restart=always
 ExecStartPre=/usr/bin/rm -f %t/%n-pid %t/%n-cid
 ExecStart=/usr/bin/podman run --conmon-pidfile %t/%n-pid --cidfile %t/%n-cid --cgroups=no-conmon -d awesome-image:latest