health check: add on-failure actions

For systems that have extreme robustness requirements (edge devices,
particularly those in difficult to access environments), it is important
that applications continue running in all circumstances. When the
application fails, Podman must restart it automatically to provide this
robustness. Otherwise, these devices may require customer IT to
physically gain access to restart, which can be prohibitively difficult.

Add a new `--on-failure` flag that supports four actions:

- **none**: Take no action.

- **kill**: Kill the container.

- **restart**: Restart the container.  Do not combine the `restart`
               action with the `--restart` flag.  When running inside of
               a systemd unit, consider using the `kill` or `stop`
               action instead to make use of systemd's restart policy.

- **stop**: Stop the container.

To remain backwards compatible, **none** is the default action.

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

cmd/podman/common/completion.go

@@ -1641,3 +1641,8 @@ func AutocompleteSSH(cmd *cobra.Command, args []string, toComplete string) ([]st
 	}
 	return []string{string(ssh.GolangMode), string(ssh.NativeMode)}, cobra.ShellCompDirectiveNoFileComp
 }
+
+// AutocompleteHealthOnFailure - action to take once the container turns unhealthy.
+func AutocompleteHealthOnFailure(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
+	return define.SupportedHealthCheckOnFailureActions, cobra.ShellCompDirectiveNoFileComp
+}

cmd/podman/common/create.go

@@ -208,6 +208,14 @@ func DefineCreateFlags(cmd *cobra.Command, cf *entities.ContainerCreateOptions,
 		)
 		_ = cmd.RegisterFlagCompletionFunc(healthTimeoutFlagName, completion.AutocompleteNone)
 
+		healthOnFailureFlagName := "health-on-failure"
+		createFlags.StringVar(
+			&cf.HealthOnFailure,
+			healthOnFailureFlagName, "none",
+			"action to take once the container turns unhealthy",
+		)
+		_ = cmd.RegisterFlagCompletionFunc(healthOnFailureFlagName, AutocompleteHealthOnFailure)
+
 		createFlags.BoolVar(
 			&cf.HTTPProxy,
 			"http-proxy", containerConfig.Containers.HTTPProxy,

docs/source/markdown/options/health-on-failure.md

@@ -0,0 +1,8 @@
+#### **--health-on-failure**=*action*
+
+Action to take once the container transitions to an unhealthy state.  The default is **none**.
+
+- **none**: Take no action.
+- **kill**: Kill the container.
+- **restart**: Restart the container.  Do not combine the `restart` action with the `--restart` flag.  When running inside of a systemd unit, consider using the `kill` or `stop` action instead to make use of systemd's restart policy.
+- **stop**: Stop the container.

docs/source/markdown/podman-create.1.md.in

@@ -185,6 +185,8 @@ Read in a line delimited file of environment variables. See **Environment** note
 
 @@option health-interval
 
+@@option health-on-failure
+
 @@option health-retries
 
 @@option health-start-period

docs/source/markdown/podman-run.1.md.in

@@ -221,6 +221,8 @@ Read in a line delimited file of environment variables. See **Environment** note
 
 @@option health-interval
 
+@@option health-on-failure
+
 @@option health-retries
 
 @@option health-start-period

libpod/container_config.go

@@ -7,6 +7,7 @@ import (
 	"github.com/containers/common/libnetwork/types"
 	"github.com/containers/common/pkg/secrets"
 	"github.com/containers/image/v5/manifest"
+	"github.com/containers/podman/v4/libpod/define"
 	"github.com/containers/podman/v4/pkg/namespaces"
 	"github.com/containers/podman/v4/pkg/specgen"
 	"github.com/containers/storage"
@@ -392,6 +393,8 @@ type ContainerMiscConfig struct {
 	Systemd *bool `json:"systemd,omitempty"`
 	// HealthCheckConfig has the health check command and related timings
 	HealthCheckConfig *manifest.Schema2HealthConfig `json:"healthcheck"`
+	// HealthCheckOnFailureAction defines an action to take once the container turns unhealthy.
+	HealthCheckOnFailureAction define.HealthCheckOnFailureAction `json:"healthcheck_on_failure_action"`
 	// PreserveFDs is a number of additional file descriptors (in addition
 	// to 0, 1, 2) that will be passed to the executed process. The total FDs
 	// passed will be 3 + PreserveFDs.

libpod/container_inspect.go

@@ -390,6 +390,8 @@ func (c *Container) generateInspectContainerConfig(spec *spec.Spec) *define.Insp
 	// leak.
 	ctrConfig.Healthcheck = c.config.HealthCheckConfig
 
+	ctrConfig.HealthcheckOnFailureAction = c.config.HealthCheckOnFailureAction.String()
+
 	ctrConfig.CreateCommand = c.config.CreateCommand
 
 	ctrConfig.Timezone = c.config.Timezone

libpod/container_validate.go

@@ -137,5 +137,9 @@ func (c *Container) validate() error {
 	if c.config.SdNotifyMode == define.SdNotifyModeIgnore && len(c.config.SdNotifySocket) > 0 {
 		return fmt.Errorf("cannot set sd-notify socket %q with sd-notify mode %q", c.config.SdNotifySocket, c.config.SdNotifyMode)
 	}
+
+	if c.config.HealthCheckOnFailureAction != define.HealthCheckOnFailureActionNone && c.config.HealthCheckConfig == nil {
+		return fmt.Errorf("cannot set on-failure action to %s without a health check", c.config.HealthCheckOnFailureAction.String())
+	}
 	return nil
 }

libpod/define/container_inspect.go

@@ -55,6 +55,8 @@ type InspectContainerConfig struct {
 	StopSignal uint `json:"StopSignal"`
 	// Configured healthcheck for the container
 	Healthcheck *manifest.Schema2HealthConfig `json:"Healthcheck,omitempty"`
+	// HealthcheckOnFailureAction defines an action to take once the container turns unhealthy.
+	HealthcheckOnFailureAction string `json:"HealthcheckOnFailureAction,omitempty"`
 	// CreateCommand is the full command plus arguments of the process the
 	// container has been created with.
 	CreateCommand []string `json:"CreateCommand,omitempty"`

libpod/define/healthchecks.go

@@ -1,5 +1,10 @@
 package define
 
+import (
+	"fmt"
+	"strings"
+)
+
 const (
 	// HealthCheckHealthy describes a healthy container
 	HealthCheckHealthy string = "healthy"
@@ -57,3 +62,72 @@ const (
 	// HealthConfigTestCmdShell runs commands with the system's default shell
 	HealthConfigTestCmdShell = "CMD-SHELL"
 )
+
+// HealthCheckOnFailureAction defines how Podman reacts when a container's health
+// status turns unhealthy.
+type HealthCheckOnFailureAction int
+
+// Healthcheck on-failure actions.
+const (
+	// HealthCheckOnFailureActionNonce instructs Podman to not react on an unhealthy status.
+	HealthCheckOnFailureActionNone = iota // Must be first iota for backwards compatibility
+	// HealthCheckOnFailureActionInvalid denotes an invalid on-failure policy.
+	HealthCheckOnFailureActionInvalid = iota
+	// HealthCheckOnFailureActionNonce instructs Podman to kill the container on an unhealthy status.
+	HealthCheckOnFailureActionKill = iota
+	// HealthCheckOnFailureActionNonce instructs Podman to restart the container on an unhealthy status.
+	HealthCheckOnFailureActionRestart = iota
+	// HealthCheckOnFailureActionNonce instructs Podman to stop the container on an unhealthy status.
+	HealthCheckOnFailureActionStop = iota
+)
+
+// String representations for on-failure actions.
+const (
+	strHealthCheckOnFailureActionNone    = "none"
+	strHealthCheckOnFailureActionInvalid = "invalid"
+	strHealthCheckOnFailureActionKill    = "kill"
+	strHealthCheckOnFailureActionRestart = "restart"
+	strHealthCheckOnFailureActionStop    = "stop"
+)
+
+// SupportedHealthCheckOnFailureActions lists all supported healthcheck restart policies.
+var SupportedHealthCheckOnFailureActions = []string{
+	strHealthCheckOnFailureActionNone,
+	strHealthCheckOnFailureActionKill,
+	strHealthCheckOnFailureActionRestart,
+	strHealthCheckOnFailureActionStop,
+}
+
+// String returns the string representation of the HealthCheckOnFailureAction.
+func (h HealthCheckOnFailureAction) String() string {
+	switch h {
+	case HealthCheckOnFailureActionNone:
+		return strHealthCheckOnFailureActionNone
+	case HealthCheckOnFailureActionKill:
+		return strHealthCheckOnFailureActionKill
+	case HealthCheckOnFailureActionRestart:
+		return strHealthCheckOnFailureActionRestart
+	case HealthCheckOnFailureActionStop:
+		return strHealthCheckOnFailureActionStop
+	default:
+		return strHealthCheckOnFailureActionInvalid
+	}
+}
+
+// ParseHealthCheckOnFailureAction parses the specified string into a HealthCheckOnFailureAction.
+// An error is returned for an invalid input.
+func ParseHealthCheckOnFailureAction(s string) (HealthCheckOnFailureAction, error) {
+	switch s {
+	case "", strHealthCheckOnFailureActionNone:
+		return HealthCheckOnFailureActionNone, nil
+	case strHealthCheckOnFailureActionKill:
+		return HealthCheckOnFailureActionKill, nil
+	case strHealthCheckOnFailureActionRestart:
+		return HealthCheckOnFailureActionRestart, nil
+	case strHealthCheckOnFailureActionStop:
+		return HealthCheckOnFailureActionStop, nil
+	default:
+		err := fmt.Errorf("invalid on-failure action %q for health check: supported actions are %s", s, strings.Join(SupportedHealthCheckOnFailureActions, ","))
+		return HealthCheckOnFailureActionInvalid, err
+	}
+}

libpod/healthcheck.go

@@ -2,6 +2,7 @@ package libpod
 
 import (
 	"bufio"
+	"context"
 	"errors"
 	"fmt"
 	"io/ioutil"
@@ -12,6 +13,7 @@ import (
 
 	"github.com/containers/podman/v4/libpod/define"
 	"github.com/sirupsen/logrus"
+	"golang.org/x/sys/unix"
 )
 
 const (
@@ -29,9 +31,14 @@ func (r *Runtime) HealthCheck(name string) (define.HealthCheckStatus, error) {
 	if err != nil {
 		return define.HealthCheckContainerNotFound, fmt.Errorf("unable to look up %s to perform a health check: %w", name, err)
 	}
+
 	hcStatus, err := checkHealthCheckCanBeRun(container)
 	if err == nil {
-		return container.runHealthCheck()
+		hcStatus, err := container.runHealthCheck()
+		if err := container.processHealthCheckStatus(hcStatus); err != nil {
+			return hcStatus, err
+		}
+		return hcStatus, err
 	}
 	return hcStatus, err
 }
@@ -127,13 +134,45 @@ func (c *Container) runHealthCheck() (define.HealthCheckStatus, error) {
 		hcResult = define.HealthCheckFailure
 		hcErr = fmt.Errorf("healthcheck command exceeded timeout of %s", c.HealthCheckConfig().Timeout.String())
 	}
+
 	hcl := newHealthCheckLog(timeStart, timeEnd, returnCode, eventLog)
 	if err := c.updateHealthCheckLog(hcl, inStartPeriod); err != nil {
 		return hcResult, fmt.Errorf("unable to update health check log %s for %s: %w", c.healthCheckLogPath(), c.ID(), err)
 	}
+
 	return hcResult, hcErr
 }
 
+func (c *Container) processHealthCheckStatus(status define.HealthCheckStatus) error {
+	if status == define.HealthCheckSuccess {
+		return nil
+	}
+
+	switch c.config.HealthCheckOnFailureAction {
+	case define.HealthCheckOnFailureActionNone: // Nothing to do
+
+	case define.HealthCheckOnFailureActionKill:
+		if err := c.Kill(uint(unix.SIGKILL)); err != nil {
+			return fmt.Errorf("killing container health-check turned unhealthy: %w", err)
+		}
+
+	case define.HealthCheckOnFailureActionRestart:
+		if err := c.RestartWithTimeout(context.Background(), c.config.StopTimeout); err != nil {
+			return fmt.Errorf("restarting container after health-check turned unhealthy: %w", err)
+		}
+
+	case define.HealthCheckOnFailureActionStop:
+		if err := c.Stop(); err != nil {
+			return fmt.Errorf("stopping container after health-check turned unhealthy: %w", err)
+		}
+
+	default: // Should not happen but better be safe than sorry
+		return fmt.Errorf("unsupported on-failure action %d", c.config.HealthCheckOnFailureAction)
+	}
+
+	return nil
+}
+
 func checkHealthCheckCanBeRun(c *Container) (define.HealthCheckStatus, error) {
 	cstate, err := c.State()
 	if err != nil {

libpod/options.go

@@ -1473,6 +1473,17 @@ func WithHealthCheck(healthCheck *manifest.Schema2HealthConfig) CtrCreateOption
 	}
 }
 
+// WithHealthCheckOnFailureAction adds an on-failure action to health-check config
+func WithHealthCheckOnFailureAction(action define.HealthCheckOnFailureAction) CtrCreateOption {
+	return func(ctr *Container) error {
+		if ctr.valid {
+			return define.ErrCtrFinalized
+		}
+		ctr.config.HealthCheckOnFailureAction = action
+		return nil
+	}
+}
+
 // WithPreserveFDs forwards from the process running Libpod into the container
 // the given number of extra FDs (starting after the standard streams) to the created container
 func WithPreserveFDs(fd uint) CtrCreateOption {

pkg/domain/entities/pods.go

@@ -212,6 +212,7 @@ type ContainerCreateOptions struct {
 	HealthRetries     uint
 	HealthStartPeriod string
 	HealthTimeout     string
+	HealthOnFailure   string
 	Hostname          string `json:"hostname,omitempty"`
 	HTTPProxy         bool
 	HostUsers         []string

pkg/specgen/generate/container_create.go

@@ -515,6 +515,10 @@ func createContainerOptions(rt *libpod.Runtime, s *specgen.SpecGenerator, pod *l
 		logrus.Debugf("New container has a health check")
 	}
 
+	if s.ContainerHealthCheckConfig.HealthCheckOnFailureAction != define.HealthCheckOnFailureActionNone {
+		options = append(options, libpod.WithHealthCheckOnFailureAction(s.ContainerHealthCheckConfig.HealthCheckOnFailureAction))
+	}
+
 	if len(s.Secrets) != 0 {
 		manager, err := rt.SecretsManager()
 		if err != nil {

pkg/specgen/specgen.go

@@ -9,6 +9,7 @@ import (
 	"github.com/containers/common/libimage"
 	nettypes "github.com/containers/common/libnetwork/types"
 	"github.com/containers/image/v5/manifest"
+	"github.com/containers/podman/v4/libpod/define"
 	"github.com/containers/storage/types"
 	spec "github.com/opencontainers/runtime-spec/specs-go"
 )
@@ -533,7 +534,8 @@ type ContainerResourceConfig struct {
 // ContainerHealthCheckConfig describes a container healthcheck with attributes
 // like command, retries, interval, start period, and timeout.
 type ContainerHealthCheckConfig struct {
-	HealthConfig *manifest.Schema2HealthConfig `json:"healthconfig,omitempty"`
+	HealthConfig               *manifest.Schema2HealthConfig     `json:"healthconfig,omitempty"`
+	HealthCheckOnFailureAction define.HealthCheckOnFailureAction `json:"health_check_on_failure_action,omitempty"`
 }
 
 // SpecGenerator creates an OCI spec and Libpod configuration options to create

pkg/specgenutil/specgen.go

@@ -265,6 +265,13 @@ func FillOutSpecGen(s *specgen.SpecGenerator, c *entities.ContainerCreateOptions
 			Test: []string{"NONE"},
 		}
 	}
+
+	onFailureAction, err := define.ParseHealthCheckOnFailureAction(c.HealthOnFailure)
+	if err != nil {
+		return err
+	}
+	s.HealthCheckOnFailureAction = onFailureAction
+
 	if err := setNamespaces(s, c); err != nil {
 		return err
 	}

test/system/220-healthcheck.bats

@@ -20,44 +20,8 @@ function _check_health {
     done
 }
 
-
 @test "podman healthcheck" {
-    # Create an image with a healthcheck script; said script will
-    # pass until the file /uh-oh gets created (by us, via exec)
-    cat >${PODMAN_TMPDIR}/healthcheck <<EOF
-#!/bin/sh
-
-if test -e /uh-oh; then
-    echo "Uh-oh on stdout!"
-    echo "Uh-oh on stderr!" >&2
-    exit 1
-else
-    echo "Life is Good on stdout"
-    echo "Life is Good on stderr" >&2
-    exit 0
-fi
-EOF
-
-    cat >${PODMAN_TMPDIR}/entrypoint <<EOF
-#!/bin/sh
-
-while :; do
-    sleep 1
-done
-EOF
-
-    cat >${PODMAN_TMPDIR}/Containerfile <<EOF
-FROM $IMAGE
-
-COPY healthcheck /healthcheck
-COPY entrypoint  /entrypoint
-
-RUN  chmod 755 /healthcheck /entrypoint
-
-CMD ["/entrypoint"]
-EOF
-
-    run_podman build -t healthcheck_i ${PODMAN_TMPDIR}
+    _build_health_check_image healthcheck_i
 
     # Run that healthcheck image.
     run_podman run -d --name healthcheck_c \
@@ -66,6 +30,9 @@ EOF
                --health-retries 3          \
                healthcheck_i
 
+    run_podman inspect healthcheck_c --format "{{.Config.HealthcheckOnFailureAction}}"
+    is "$output" "none" "default on-failure action is none"
+
     # We can't check for 'starting' because a 1-second interval is too
     # short; it could run healthcheck before we get to our first check.
     #
@@ -109,4 +76,59 @@ Log[-1].Output   | \"Uh-oh on stdout!\\\nUh-oh on stderr!\"
     run_podman rmi   healthcheck_i
 }
 
+@test "podman healthcheck --health-on-failure" {
+    run_podman 125 create --health-on-failure=kill $IMAGE
+    is "$output" "Error: cannot set on-failure action to kill without a health check"
+
+    ctr="healthcheck_c"
+    img="healthcheck_i"
+
+    for policy in none kill restart stop;do
+	if [[ $policy == "none" ]];then
+	    # Do not remove the /uh-oh file for `none` as we want to
+	    # demonstrate that no action was taken
+            _build_health_check_image $img
+        else
+            _build_health_check_image $img cleanfile
+        fi
+
+        # Run that healthcheck image.
+        run_podman run -d --name $ctr      \
+               --health-cmd /healthcheck   \
+               --health-on-failure=$policy \
+               $img
+
+        # healthcheck should succeed
+        run_podman healthcheck run $ctr
+
+        # Now cause the healthcheck to fail
+        run_podman exec $ctr touch /uh-oh
+
+        # healthcheck should now fail, with exit status 1 and 'unhealthy' output
+        run_podman 1 healthcheck run $ctr
+	# FIXME: #15691 - `healthcheck run` may emit an error log that the timer already exists
+        is "$output" ".*unhealthy.*" "output from 'podman healthcheck run'"
+
+        run_podman inspect $ctr --format "{{.State.Status}} {{.Config.HealthcheckOnFailureAction}}"
+	if [[ $policy == "restart" ]];then
+	    # Container has been restarted and health check works again
+            is "$output" "running $policy" "container has been restarted"
+            run_podman healthcheck run $ctr
+        elif [[ $policy == "none" ]];then
+            # Container is still running and health check still broken
+            is "$output" "running $policy" "container continued running"
+            run_podman 1 healthcheck run $ctr
+	    # FIXME: #15691 - `healthcheck run` may emit an error log that the timer already exists
+            is "$output" ".*unhealthy.*" "output from 'podman healthcheck run'"
+	else
+	    # kill and stop yield the container into a non-running state
+            is "$output" ".* $policy" "container was stopped/killed"
+            assert "$output" != "running $policy"
+        fi
+
+        run_podman rm -f -t0 $ctr
+        run_podman rmi -f $img
+    done
+}
+
 # vim: filetype=sh

test/system/250-systemd.bats

@@ -304,6 +304,57 @@ LISTEN_FDNAMES=listen_fdnames" | sort)
     run_podman network rm -f $netname
 }
 
+@test "podman create --health-on-failure=kill" {
+    img="healthcheck_i"
+    _build_health_check_image $img
+
+    cname=$(random_string)
+    run_podman create --name $cname      \
+               --health-cmd /healthcheck \
+               --health-on-failure=kill  \
+               --restart=on-failure      \
+               $img
+
+    # run container in systemd unit
+    service_setup
+
+    run_podman container inspect $cname --format "{{.ID}}"
+    oldID="$output"
+
+    run_podman healthcheck run $cname
+
+    # Now cause the healthcheck to fail
+    run_podman exec $cname touch /uh-oh
+
+    # healthcheck should now fail, with exit status 1 and 'unhealthy' output
+    run_podman 1 healthcheck run $cname
+    is "$output" "unhealthy" "output from 'podman healthcheck run'"
+
+    # What is expected to happen now:
+    #  1) The container gets killed as the health check has failed
+    #  2) Systemd restarts the service as the restart policy is set to "on-failure"
+    #  3) The /uh-oh file is gone and $cname has another ID
+
+    # Wait at most 10 seconds for the service to be restarted
+    local timeout=10
+    while [[ $timeout -gt 1 ]]; do
+        run_podman '?' container inspect $cname
+        if [[ $status == 0 ]]; then
+            if [[ "$output" != "$oldID" ]]; then
+                break
+            fi
+        fi
+        sleep 1
+        let timeout=$timeout-1
+    done
+
+    run_podman healthcheck run $cname
+
+    # stop systemd container
+    service_cleanup
+    run_podman rmi -f $img
+}
+
 @test "podman-kube@.service template" {
     install_kube_template
     # Create the YAMl file

test/system/helpers.bash

@@ -894,5 +894,59 @@ function _podman_commands() {
     awk '/^Available Commands:/{ok=1;next}/^Options:/{ok=0}ok { print $1 }' <<<"$output" | grep .
 }
 
+###############################
+#  _build_health_check_image  #  Builds a container image with a configured health check
+###############################
+#
+# The health check will fail once the /uh-oh file exists.
+#
+# First argument is the desired name of the image
+# Second argument, if present and non-null, forces removal of the /uh-oh file once the check failed; this way the container can be restarted
+#
+
+function _build_health_check_image {
+    local imagename="$1"
+    local cleanfile=""
+
+    if [[ ! -z "$2" ]]; then
+        cleanfile="rm -f /uh-oh"
+    fi
+    # Create an image with a healthcheck script; said script will
+    # pass until the file /uh-oh gets created (by us, via exec)
+    cat >${PODMAN_TMPDIR}/healthcheck <<EOF
+#!/bin/sh
+
+if test -e /uh-oh; then
+    echo "Uh-oh on stdout!"
+    echo "Uh-oh on stderr!" >&2
+    ${cleanfile}
+    exit 1
+else
+    echo "Life is Good on stdout"
+    echo "Life is Good on stderr" >&2
+    exit 0
+fi
+EOF
+
+    cat >${PODMAN_TMPDIR}/entrypoint <<EOF
+#!/bin/sh
+
+trap 'echo Received SIGTERM, finishing; exit' SIGTERM; echo WAITING; while :; do sleep 0.1; done
+EOF
+
+    cat >${PODMAN_TMPDIR}/Containerfile <<EOF
+FROM $IMAGE
+
+COPY healthcheck /healthcheck
+COPY entrypoint  /entrypoint
+
+RUN  chmod 755 /healthcheck /entrypoint
+
+CMD ["/entrypoint"]
+EOF
+
+    run_podman build -t $imagename ${PODMAN_TMPDIR}
+}
+
 # END   miscellaneous tools
 ###############################################################################