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>

1 files changed, 45 insertions, 14 deletions

diff --git a/cmd/podman/shared/create.go b/cmd/podman/shared/create.go
index 8968f10e8..cec837af6 100644
--- a/cmd/podman/shared/create.go
+++ b/cmd/podman/shared/create.go
@@ -18,6 +18,7 @@ import (
 	"github.com/containers/libpod/libpod"
 	"github.com/containers/libpod/libpod/image"
 	ann "github.com/containers/libpod/pkg/annotations"
+	"github.com/containers/libpod/pkg/autoupdate"
 	envLib "github.com/containers/libpod/pkg/env"
 	"github.com/containers/libpod/pkg/errorhandling"
 	"github.com/containers/libpod/pkg/inspect"
@@ -25,6 +26,7 @@ import (
 	"github.com/containers/libpod/pkg/rootless"
 	"github.com/containers/libpod/pkg/seccomp"
 	cc "github.com/containers/libpod/pkg/spec"
+	systemdGen "github.com/containers/libpod/pkg/systemd/generate"
 	"github.com/containers/libpod/pkg/util"
 	"github.com/docker/go-connections/nat"
 	"github.com/docker/go-units"
@@ -69,6 +71,7 @@ func CreateContainer(ctx context.Context, c *GenericCLIResults, runtime *libpod.
 	}
 
 	imageName := ""
+	rawImageName := ""
 	var imageData *inspect.ImageData = nil
 
 	// Set the storage if there is no rootfs specified
@@ -78,9 +81,8 @@ func CreateContainer(ctx context.Context, c *GenericCLIResults, runtime *libpod.
 			writer = os.Stderr
 		}
 
-		name := ""
 		if len(c.InputArgs) != 0 {
-			name = c.InputArgs[0]
+			rawImageName = c.InputArgs[0]
 		} else {
 			return nil, nil, errors.Errorf("error, image name not provided")
 		}
@@ -97,7 +99,7 @@ func CreateContainer(ctx context.Context, c *GenericCLIResults, runtime *libpod.
 			ArchitectureChoice: overrideArch,
 		}
 
-		newImage, err := runtime.ImageRuntime().New(ctx, name, rtc.SignaturePolicyPath, c.String("authfile"), writer, &dockerRegistryOptions, image.SigningOptions{}, nil, pullType)
+		newImage, err := runtime.ImageRuntime().New(ctx, rawImageName, rtc.SignaturePolicyPath, c.String("authfile"), writer, &dockerRegistryOptions, image.SigningOptions{}, nil, pullType)
 		if err != nil {
 			return nil, nil, err
 		}
@@ -174,11 +176,32 @@ func CreateContainer(ctx context.Context, c *GenericCLIResults, runtime *libpod.
 		}
 	}
 
-	createConfig, err := ParseCreateOpts(ctx, c, runtime, imageName, imageData)
+	createConfig, err := ParseCreateOpts(ctx, c, runtime, imageName, rawImageName, imageData)
 	if err != nil {
 		return nil, nil, err
 	}
 
+	// (VR): Ideally we perform the checks _before_ pulling the image but that
+	// would require some bigger code refactoring of `ParseCreateOpts` and the
+	// logic here.  But as the creation code will be consolidated in the future
+	// and given auto updates are experimental, we can live with that for now.
+	// In the end, the user may only need to correct the policy or the raw image
+	// name.
+	autoUpdatePolicy, autoUpdatePolicySpecified := createConfig.Labels[autoupdate.Label]
+	if autoUpdatePolicySpecified {
+		if _, err := autoupdate.LookupPolicy(autoUpdatePolicy); err != nil {
+			return nil, nil, err
+		}
+		// Now we need to make sure we're having a fully-qualified image reference.
+		if rootfs != "" {
+			return nil, nil, errors.Errorf("auto updates do not work with --rootfs")
+		}
+		// Make sure the input image is a docker.
+		if err := autoupdate.ValidateImageReference(rawImageName); err != nil {
+			return nil, nil, err
+		}
+	}
+
 	// Because parseCreateOpts does derive anything from the image, we add health check
 	// at this point. The rest is done by WithOptions.
 	createConfig.HealthCheck = healthCheck
@@ -270,7 +293,7 @@ func configurePod(c *GenericCLIResults, runtime *libpod.Runtime, namespaces map[
 
 // Parses CLI options related to container creation into a config which can be
 // parsed into an OCI runtime spec
-func ParseCreateOpts(ctx context.Context, c *GenericCLIResults, runtime *libpod.Runtime, imageName string, data *inspect.ImageData) (*cc.CreateConfig, error) {
+func ParseCreateOpts(ctx context.Context, c *GenericCLIResults, runtime *libpod.Runtime, imageName string, rawImageName string, data *inspect.ImageData) (*cc.CreateConfig, error) {
 	var (
 		inputCommand, command                                    []string
 		memoryLimit, memoryReservation, memorySwap, memoryKernel int64
@@ -481,12 +504,15 @@ func ParseCreateOpts(ctx context.Context, c *GenericCLIResults, runtime *libpod.
 		"container": "podman",
 	}
 
+	// First transform the os env into a map. We need it for the labels later in
+	// any case.
+	osEnv, err := envLib.ParseSlice(os.Environ())
+	if err != nil {
+		return nil, errors.Wrap(err, "error parsing host environment variables")
+	}
+
 	// Start with env-host
 	if c.Bool("env-host") {
-		osEnv, err := envLib.ParseSlice(os.Environ())
-		if err != nil {
-			return nil, errors.Wrap(err, "error parsing host environment variables")
-		}
 		env = envLib.Join(env, osEnv)
 	}
 
@@ -534,6 +560,10 @@ func ParseCreateOpts(ctx context.Context, c *GenericCLIResults, runtime *libpod.
 		}
 	}
 
+	if systemdUnit, exists := osEnv[systemdGen.EnvVariable]; exists {
+		labels[systemdGen.EnvVariable] = systemdUnit
+	}
+
 	// ANNOTATIONS
 	annotations := make(map[string]string)
 
@@ -764,11 +794,12 @@ func ParseCreateOpts(ctx context.Context, c *GenericCLIResults, runtime *libpod.
 		Entrypoint:        entrypoint,
 		Env:               env,
 		// ExposedPorts:   ports,
-		Init:        c.Bool("init"),
-		InitPath:    c.String("init-path"),
-		Image:       imageName,
-		ImageID:     imageID,
-		Interactive: c.Bool("interactive"),
+		Init:         c.Bool("init"),
+		InitPath:     c.String("init-path"),
+		Image:        imageName,
+		RawImageName: rawImageName,
+		ImageID:      imageID,
+		Interactive:  c.Bool("interactive"),
 		// IP6Address:     c.String("ipv6"), // Not implemented yet - needs CNI support for static v6
 		Labels: labels,
 		// LinkLocalIP:    c.StringSlice("link-local-ip"), // Not implemented yet