feat: add initial scheduled task implementation

This functionality enables users to manage a global crontab for the Dokku user that contains all scheduled tasks across all apps. Alternative schedulers can implement cron tasks as desired.
2021-01-18 18:15:42 -05:00
parent e00e498e50
commit f7ef14d737
23 changed files with 1026 additions and 391 deletions
--- a/plugins/00_dokku-standard/subcommands/run
+++ b/plugins/00_dokku-standard/subcommands/run
@@ -8,11 +8,24 @@ cmd-run() {
  declare cmd="run"
  [[ "$1" == "$cmd" ]] && shift 1
  declare APP=""
-
+  local SCHEDULER_ID
  declare -a RUN_ENV
  RUN_ENV=()
  while [[ $# -gt 0 ]]; do
    case $1 in
+      --cron-id=*)
+        local arg=$(printf "%s" "$1" | sed -E 's/(^--cron-id=)//g')
+        SCHEDULER_ID+=("$arg")
+        shift
+        ;;
+      --cron-id)
+        if [[ ! $2 ]]; then
+          dokku_log_warn "expected $1 to have an argument"
+          break
+        fi
+        CRON_ID+=("$2")
+        shift 2
+        ;;
      -e=* | --env=*)
        local arg=$(printf "%s" "$1" | sed -E 's/(^-e=)|(^--env=)//g')
        RUN_ENV+=("$arg")
@@ -37,7 +50,7 @@ cmd-run() {
  verify_app_name "$APP"

  local DOKKU_SCHEDULER=$(get_app_scheduler "$APP")
-  plugn trigger scheduler-run "$DOKKU_SCHEDULER" "$APP" "${#RUN_ENV[@]}" "${RUN_ENV[@]}" "$@"
+  DOKKU_CRON_ID="$CRON_ID" plugn trigger scheduler-run "$DOKKU_SCHEDULER" "$APP" "${#RUN_ENV[@]}" "${RUN_ENV[@]}" "$@"
 }

 cmd-run "$@"
--- a/plugins/app-json/.gitignore
+++ b/plugins/app-json/.gitignore
@@ -2,3 +2,4 @@
 /triggers
 /pre-*
 /post-*
+/install
--- a/plugins/app-json/Makefile
+++ b/plugins/app-json/Makefile
@@ -1,4 +1,4 @@
-TRIGGERS = triggers/post-deploy triggers/pre-deploy
+TRIGGERS = triggers/install triggers/post-delete triggers/post-deploy triggers/pre-deploy
 BUILD = triggers
 PLUGIN_NAME = app-json

--- a/plugins/app-json/appjson.go
+++ b/plugins/app-json/appjson.go
@@ -1,22 +1,14 @@
 package appjson

 import (
-	"bytes"
-	"context"
-	"encoding/json"
-	"errors"
-	"fmt"
-	"io/ioutil"
-	"os"
-	"strings"
+	"path/filepath"

 	"github.com/dokku/dokku/plugins/common"
-	shellquote "github.com/kballard/go-shellquote"
-	"golang.org/x/sync/errgroup"
 )

 // AppJSON is a struct that represents an app.json file as understood by Dokku
 type AppJSON struct {
+	Cron    []CronCommand `json:"cron"`
 	Scripts struct {
 		Dokku struct {
 			Predeploy  string `json:"predeploy"`
@@ -25,382 +17,18 @@ type AppJSON struct {
 	} `json:"scripts"`
 }

-func constructScript(command string, shell string, isHerokuishImage bool, hasEntrypoint bool) []string {
-	if hasEntrypoint {
-		words, err := shellquote.Split(strings.TrimSpace(command))
-		if err != nil {
-			common.LogWarn(fmt.Sprintf("Skipping command construction for app with ENTRYPOINT: %v", err.Error()))
-			return nil
-		}
-		return words
-	}
-
-	script := []string{"set -eo pipefail;"}
-	if os.Getenv("DOKKU_TRACE") == "1" {
-		script = append(script, "set -x;")
-	}
-
-	if isHerokuishImage {
-		script = append(script, []string{
-			"if [[ -d '/app' ]]; then",
-			"  export HOME=/app;",
-			"  cd $HOME;",
-			"fi;",
-			"if [[ -d '/app/.profile.d' ]]; then",
-			"  for file in /app/.profile.d/*; do source $file; done;",
-			"fi;",
-
-			"if [[ -d '/cache' ]]; then",
-			"  rm -rf /tmp/cache ;",
-			"  ln -sf /cache /tmp/cache;",
-			"fi;",
-		}...)
-	}
-
-	if strings.HasPrefix(command, "/") {
-		commandBin := strings.Split(command, " ")[0]
-		script = append(script, []string{
-			fmt.Sprintf("if [[ ! -x \"%s\" ]]; then", commandBin),
-			"  echo specified binary is not executable;",
-			"  exit 1;",
-			"fi;",
-		}...)
-	}
-
-	script = append(script, fmt.Sprintf("%s || exit 1;", command))
-
-	if isHerokuishImage {
-		script = append(script, []string{
-			"if [[ -d '/cache' ]]; then",
-			"  rm -f /tmp/cache;",
-			"fi;",
-		}...)
-	}
-
-	return []string{shell, "-c", strings.Join(script, " ")}
+// CronCommand is a struct that represents a single cron command from an app.json file
+type CronCommand struct {
+	Command  string `json:"command"`
+	Schedule string `json:"schedule"`
 }

-// getPhaseScript extracts app.json from app image and returns the appropriate json key/value
-func getPhaseScript(appName string, image string, phase string) (string, error) {
-	appJSONFile, err := ioutil.TempFile(os.TempDir(), fmt.Sprintf("dokku-%s-%s", common.MustGetEnv("DOKKU_PID"), "getPhaseScript"))
-	if err != nil {
-		return "", fmt.Errorf("Cannot create temporary file: %v", err)
-	}
-
-	defer os.Remove(appJSONFile.Name())
-
-	common.CopyFromImage(appName, image, "app.json", appJSONFile.Name())
-	if !common.FileExists(appJSONFile.Name()) {
-		return "", nil
-	}
-
-	b, err := ioutil.ReadFile(appJSONFile.Name())
-	if err != nil {
-		return "", fmt.Errorf("Cannot read app.json file: %v", err)
-	}
-
-	if strings.TrimSpace(string(b)) == "" {
-		return "", nil
-	}
-
-	var appJSON AppJSON
-	if err = json.Unmarshal(b, &appJSON); err != nil {
-		return "", fmt.Errorf("Cannot parse app.json: %v", err)
-	}
-
-	if phase == "predeploy" {
-		return appJSON.Scripts.Dokku.Predeploy, nil
-	}
-
-	return appJSON.Scripts.Dokku.Postdeploy, nil
+// GetAppjsonDirectory returns the directory containing a given app's extracted app.json file
+func GetAppjsonDirectory(appName string) string {
+	return filepath.Join(common.MustGetEnv("DOKKU_LIB_ROOT"), "data", "app-json", appName)
 }

-// getReleaseCommand extracts the release command from a given app's procfile
-func getReleaseCommand(appName string, image string) string {
-	err := common.SuppressOutput(func() error {
-		return common.PlugnTrigger("procfile-extract", []string{appName, image}...)
-	})
-
-	if err != nil {
-		return ""
-	}
-
-	processType := "release"
-	port := "5000"
-	b, _ := common.PlugnTriggerOutput("procfile-get-command", []string{appName, processType, port}...)
-	return strings.TrimSpace(string(b[:]))
-}
-
-func getDokkuAppShell(appName string) string {
-	shell := "/bin/bash"
-	globalShell := ""
-	appShell := ""
-
-	ctx := context.Background()
-	errs, ctx := errgroup.WithContext(ctx)
-	errs.Go(func() error {
-		b, _ := common.PlugnTriggerOutput("config-get-global", []string{"DOKKU_APP_SHELL"}...)
-		globalShell = strings.TrimSpace(string(b[:]))
-		return nil
-	})
-	errs.Go(func() error {
-		b, _ := common.PlugnTriggerOutput("config-global", []string{"DOKKU_APP_SHELL"}...)
-		appShell = strings.TrimSpace(string(b[:]))
-		return nil
-	})
-
-	errs.Wait()
-	if appShell != "" {
-		shell = appShell
-	} else if globalShell != "" {
-		shell = globalShell
-	}
-
-	return shell
-}
-
-func executeScript(appName string, imageTag string, phase string) error {
-	common.LogInfo1(fmt.Sprintf("Checking for %s task", phase))
-	image, err := common.GetDeployingAppImageName(appName, imageTag, "")
-	if err != nil {
-		common.LogFail(err.Error())
-	}
-	command := ""
-	phaseSource := ""
-	if phase == "release" {
-		command = getReleaseCommand(appName, image)
-		phaseSource = "Procfile"
-	} else {
-		var err error
-		phaseSource = "app.json"
-		if command, err = getPhaseScript(appName, image, phase); err != nil {
-			common.LogExclaim(err.Error())
-		}
-	}
-
-	if command == "" {
-		common.LogVerbose(fmt.Sprintf("No %s task found, skipping", phase))
-		return nil
-	}
-
-	common.LogInfo1(fmt.Sprintf("Executing %s task from %s: %s", phase, phaseSource, command))
-	isHerokuishImage := common.IsImageHerokuishBased(image, appName)
-	dockerfileEntrypoint := ""
-	dockerfileCommand := ""
-	if !isHerokuishImage {
-		dockerfileEntrypoint, _ = getEntrypointFromImage(image)
-		dockerfileCommand, _ = getCommandFromImage(image)
-	}
-
-	hasEntrypoint := dockerfileEntrypoint != ""
-	dokkuAppShell := getDokkuAppShell(appName)
-	script := constructScript(command, dokkuAppShell, isHerokuishImage, hasEntrypoint)
-
-	imageSourceType := "dockerfile"
-	if isHerokuishImage {
-		imageSourceType = "herokuish"
-	}
-
-	cacheDir := fmt.Sprintf("%s/cache", common.AppRoot(appName))
-	cacheHostDir := fmt.Sprintf("%s/cache", common.AppHostRoot(appName))
-	if !common.DirectoryExists(cacheDir) {
-		os.MkdirAll(cacheDir, 0755)
-	}
-
-	var dockerArgs []string
-	if b, err := common.PlugnTriggerSetup("docker-args-deploy", []string{appName, imageTag}...).SetInput("").Output(); err == nil {
-		words, err := shellquote.Split(strings.TrimSpace(string(b[:])))
-		if err != nil {
-			return err
-		}
-
-		dockerArgs = append(dockerArgs, words...)
-	}
-
-	if b, err := common.PlugnTriggerSetup("docker-args-process-deploy", []string{appName, imageSourceType, imageTag}...).SetInput("").Output(); err == nil {
-		words, err := shellquote.Split(strings.TrimSpace(string(b[:])))
-		if err != nil {
-			return err
-		}
-
-		dockerArgs = append(dockerArgs, words...)
-	}
-
-	filteredArgs := []string{"restart", "cpus", "memory", "memory-swap", "memory-reservation", "gpus"}
-	for _, filteredArg := range filteredArgs {
-		// re := regexp.MustCompile("--" + filteredArg + "=[0-9A-Za-z!\"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~]+ ")
-
-		var filteredDockerArgs []string
-		for _, dockerArg := range dockerArgs {
-			if !strings.HasPrefix(dockerArg, "--"+filteredArg+"=") {
-				filteredDockerArgs = append(filteredDockerArgs, dockerArg)
-			}
-		}
-
-		dockerArgs = filteredDockerArgs
-	}
-
-	dockerArgs = append(dockerArgs, "--label=dokku_phase_script="+phase)
-	dockerArgs = append(dockerArgs, "-v", cacheHostDir+":/cache")
-	if os.Getenv("DOKKU_TRACE") != "" {
-		dockerArgs = append(dockerArgs, "--env", "DOKKU_TRACE="+os.Getenv("DOKKU_TRACE"))
-	}
-
-	containerID, err := createdContainerID(appName, dockerArgs, image, script, phase)
-	if err != nil {
-		common.LogFail(fmt.Sprintf("Failed to create %s execution container: %s", phase, err.Error()))
-	}
-
-	if !waitForExecution(containerID) {
-		common.LogInfo2Quiet(fmt.Sprintf("Start of %s %s task (%s) output", appName, phase, containerID[0:9]))
-		common.LogVerboseQuietContainerLogs(containerID)
-		common.LogInfo2Quiet(fmt.Sprintf("End of %s %s task (%s) output", appName, phase, containerID[0:9]))
-		common.LogFail(fmt.Sprintf("Execution of %s task failed: %s", phase, command))
-	}
-
-	common.LogInfo2Quiet(fmt.Sprintf("Start of %s %s task (%s) output", appName, phase, containerID[0:9]))
-	common.LogVerboseQuietContainerLogs(containerID)
-	common.LogInfo2Quiet(fmt.Sprintf("End of %s %s task (%s) output", appName, phase, containerID[0:9]))
-
-	if phase != "predeploy" {
-		return nil
-	}
-
-	commitArgs := []string{"container", "commit"}
-	if !isHerokuishImage {
-		if dockerfileEntrypoint != "" {
-			commitArgs = append(commitArgs, "--change", dockerfileEntrypoint)
-		}
-
-		if dockerfileCommand != "" {
-			commitArgs = append(commitArgs, "--change", dockerfileCommand)
-		}
-	}
-
-	commitArgs = append(commitArgs, []string{
-		"--change",
-		"LABEL org.label-schema.schema-version=1.0",
-		"--change",
-		"LABEL org.label-schema.vendor=dokku",
-		"--change",
-		fmt.Sprintf("LABEL com.dokku.app-name=%s", appName),
-		"--change",
-		fmt.Sprintf("LABEL com.dokku.%s-phase=true", phase),
-	}...)
-	commitArgs = append(commitArgs, containerID, image)
-	containerCommitCmd := common.NewShellCmdWithArgs(
-		common.DockerBin(),
-		commitArgs...,
-	)
-	containerCommitCmd.ShowOutput = false
-	containerCommitCmd.Command.Stderr = os.Stderr
-	if !containerCommitCmd.Execute() {
-		common.LogFail(fmt.Sprintf("Commiting of '%s' to image failed: %s", phase, command))
-	}
-
-	return common.PlugnTrigger("scheduler-register-retired", []string{appName, containerID}...)
-}
-
-func getEntrypointFromImage(image string) (string, error) {
-	output, err := common.DockerInspect(image, "{{json .Config.Entrypoint}}")
-	if err != nil {
-		return "", err
-	}
-	if output == "null" {
-		return "", err
-	}
-
-	var entrypoint []string
-	if err = json.Unmarshal([]byte(output), &entrypoint); err != nil {
-		return "", err
-	}
-
-	if len(entrypoint) == 3 && entrypoint[0] == "/bin/sh" && entrypoint[1] == "-c" {
-		return fmt.Sprintf("ENTRYPOINT %s", entrypoint[2]), nil
-	}
-
-	serializedEntrypoint, err := json.Marshal(entrypoint)
-	return fmt.Sprintf("ENTRYPOINT %s", string(serializedEntrypoint)), err
-}
-
-func getCommandFromImage(image string) (string, error) {
-	output, err := common.DockerInspect(image, "{{json .Config.Cmd}}")
-	if err != nil {
-		return "", err
-	}
-	if output == "null" {
-		return "", err
-	}
-
-	var command []string
-	if err = json.Unmarshal([]byte(output), &command); err != nil {
-		return "", err
-	}
-
-	if len(command) == 3 && command[0] == "/bin/sh" && command[1] == "-c" {
-		return fmt.Sprintf("CMD %s", command[2]), nil
-	}
-
-	serializedEntrypoint, err := json.Marshal(command)
-	return fmt.Sprintf("CMD %s", string(serializedEntrypoint)), err
-}
-
-func waitForExecution(containerID string) bool {
-	containerStartCmd := common.NewShellCmdWithArgs(
-		common.DockerBin(),
-		"container",
-		"start",
-		containerID,
-	)
-	containerStartCmd.ShowOutput = false
-	containerStartCmd.Command.Stderr = os.Stderr
-	if !containerStartCmd.Execute() {
-		return false
-	}
-
-	containerWaitCmd := common.NewShellCmdWithArgs(
-		common.DockerBin(),
-		"container",
-		"wait",
-		containerID,
-	)
-
-	containerWaitCmd.ShowOutput = false
-	containerWaitCmd.Command.Stderr = os.Stderr
-	b, err := containerWaitCmd.Output()
-	if err != nil {
-		return false
-	}
-
-	containerExitCode := strings.TrimSpace(string(b[:]))
-	return containerExitCode == "0"
-}
-
-func createdContainerID(appName string, dockerArgs []string, image string, command []string, phase string) (string, error) {
-	runLabelArgs := fmt.Sprintf("--label=com.dokku.app-name=%s", appName)
-
-	arguments := strings.Split(common.MustGetEnv("DOKKU_GLOBAL_RUN_ARGS"), " ")
-	arguments = append(arguments, runLabelArgs)
-	arguments = append(arguments, dockerArgs...)
-
-	arguments = append([]string{"container", "create"}, arguments...)
-	arguments = append(arguments, image)
-	arguments = append(arguments, command...)
-
-	containerCreateCmd := common.NewShellCmdWithArgs(
-		common.DockerBin(),
-		arguments...,
-	)
-	var stderr bytes.Buffer
-	containerCreateCmd.ShowOutput = false
-	containerCreateCmd.Command.Stderr = &stderr
-
-	b, err := containerCreateCmd.Output()
-	if err != nil {
-		return "", errors.New(stderr.String())
-	}
-
-	containerID := strings.TrimSpace(string(b))
-	err = common.PlugnTrigger("post-container-create", []string{"app", appName, containerID, phase}...)
-	return containerID, err
+// GetAppjsonPath returns the path to a given app's extracted app.json file
+func GetAppjsonPath(appName string) string {
+	return filepath.Join(GetAppjsonDirectory(appName), "app.json")
 }
--- a/plugins/app-json/functions.go
+++ b/plugins/app-json/functions.go
@@ -0,0 +1,409 @@
+package appjson
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/dokku/dokku/plugins/common"
+	shellquote "github.com/kballard/go-shellquote"
+	"golang.org/x/sync/errgroup"
+)
+
+func constructScript(command string, shell string, isHerokuishImage bool, hasEntrypoint bool) []string {
+	if hasEntrypoint {
+		words, err := shellquote.Split(strings.TrimSpace(command))
+		if err != nil {
+			common.LogWarn(fmt.Sprintf("Skipping command construction for app with ENTRYPOINT: %v", err.Error()))
+			return nil
+		}
+		return words
+	}
+
+	script := []string{"set -eo pipefail;"}
+	if os.Getenv("DOKKU_TRACE") == "1" {
+		script = append(script, "set -x;")
+	}
+
+	if isHerokuishImage {
+		script = append(script, []string{
+			"if [[ -d '/app' ]]; then",
+			"  export HOME=/app;",
+			"  cd $HOME;",
+			"fi;",
+			"if [[ -d '/app/.profile.d' ]]; then",
+			"  for file in /app/.profile.d/*; do source $file; done;",
+			"fi;",
+
+			"if [[ -d '/cache' ]]; then",
+			"  rm -rf /tmp/cache ;",
+			"  ln -sf /cache /tmp/cache;",
+			"fi;",
+		}...)
+	}
+
+	if strings.HasPrefix(command, "/") {
+		commandBin := strings.Split(command, " ")[0]
+		script = append(script, []string{
+			fmt.Sprintf("if [[ ! -x \"%s\" ]]; then", commandBin),
+			"  echo specified binary is not executable;",
+			"  exit 1;",
+			"fi;",
+		}...)
+	}
+
+	script = append(script, fmt.Sprintf("%s || exit 1;", command))
+
+	if isHerokuishImage {
+		script = append(script, []string{
+			"if [[ -d '/cache' ]]; then",
+			"  rm -f /tmp/cache;",
+			"fi;",
+		}...)
+	}
+
+	return []string{shell, "-c", strings.Join(script, " ")}
+}
+
+// getPhaseScript extracts app.json from app image and returns the appropriate json key/value
+func getPhaseScript(appName string, phase string) (string, error) {
+	if !common.FileExists(GetAppjsonPath(appName)) {
+		return "", nil
+	}
+
+	b, err := ioutil.ReadFile(GetAppjsonPath(appName))
+	if err != nil {
+		return "", fmt.Errorf("Cannot read app.json file: %v", err)
+	}
+
+	if strings.TrimSpace(string(b)) == "" {
+		return "", nil
+	}
+
+	var appJSON AppJSON
+	if err = json.Unmarshal(b, &appJSON); err != nil {
+		return "", fmt.Errorf("Cannot parse app.json: %v", err)
+	}
+
+	if phase == "predeploy" {
+		return appJSON.Scripts.Dokku.Predeploy, nil
+	}
+
+	return appJSON.Scripts.Dokku.Postdeploy, nil
+}
+
+// getReleaseCommand extracts the release command from a given app's procfile
+func getReleaseCommand(appName string, image string) string {
+	err := common.SuppressOutput(func() error {
+		return common.PlugnTrigger("procfile-extract", []string{appName, image}...)
+	})
+
+	if err != nil {
+		return ""
+	}
+
+	processType := "release"
+	port := "5000"
+	b, _ := common.PlugnTriggerOutput("procfile-get-command", []string{appName, processType, port}...)
+	return strings.TrimSpace(string(b[:]))
+}
+
+func getDokkuAppShell(appName string) string {
+	shell := "/bin/bash"
+	globalShell := ""
+	appShell := ""
+
+	ctx := context.Background()
+	errs, ctx := errgroup.WithContext(ctx)
+	errs.Go(func() error {
+		b, _ := common.PlugnTriggerOutput("config-get-global", []string{"DOKKU_APP_SHELL"}...)
+		globalShell = strings.TrimSpace(string(b[:]))
+		return nil
+	})
+	errs.Go(func() error {
+		b, _ := common.PlugnTriggerOutput("config-global", []string{"DOKKU_APP_SHELL"}...)
+		appShell = strings.TrimSpace(string(b[:]))
+		return nil
+	})
+
+	errs.Wait()
+	if appShell != "" {
+		shell = appShell
+	} else if globalShell != "" {
+		shell = globalShell
+	}
+
+	return shell
+}
+
+func executeScript(appName string, image string, imageTag string, phase string) error {
+	common.LogInfo1(fmt.Sprintf("Checking for %s task", phase))
+	command := ""
+	phaseSource := ""
+	if phase == "release" {
+		command = getReleaseCommand(appName, image)
+		phaseSource = "Procfile"
+	} else {
+		var err error
+		phaseSource = "app.json"
+		if command, err = getPhaseScript(appName, phase); err != nil {
+			common.LogExclaim(err.Error())
+		}
+	}
+
+	if command == "" {
+		common.LogVerbose(fmt.Sprintf("No %s task found, skipping", phase))
+		return nil
+	}
+
+	common.LogInfo1(fmt.Sprintf("Executing %s task from %s: %s", phase, phaseSource, command))
+	isHerokuishImage := common.IsImageHerokuishBased(image, appName)
+	dockerfileEntrypoint := ""
+	dockerfileCommand := ""
+	if !isHerokuishImage {
+		dockerfileEntrypoint, _ = getEntrypointFromImage(image)
+		dockerfileCommand, _ = getCommandFromImage(image)
+	}
+
+	hasEntrypoint := dockerfileEntrypoint != ""
+	dokkuAppShell := getDokkuAppShell(appName)
+	script := constructScript(command, dokkuAppShell, isHerokuishImage, hasEntrypoint)
+
+	imageSourceType := "dockerfile"
+	if isHerokuishImage {
+		imageSourceType = "herokuish"
+	}
+
+	cacheDir := fmt.Sprintf("%s/cache", common.AppRoot(appName))
+	cacheHostDir := fmt.Sprintf("%s/cache", common.AppHostRoot(appName))
+	if !common.DirectoryExists(cacheDir) {
+		os.MkdirAll(cacheDir, 0755)
+	}
+
+	var dockerArgs []string
+	if b, err := common.PlugnTriggerSetup("docker-args-deploy", []string{appName, imageTag}...).SetInput("").Output(); err == nil {
+		words, err := shellquote.Split(strings.TrimSpace(string(b[:])))
+		if err != nil {
+			return err
+		}
+
+		dockerArgs = append(dockerArgs, words...)
+	}
+
+	if b, err := common.PlugnTriggerSetup("docker-args-process-deploy", []string{appName, imageSourceType, imageTag}...).SetInput("").Output(); err == nil {
+		words, err := shellquote.Split(strings.TrimSpace(string(b[:])))
+		if err != nil {
+			return err
+		}
+
+		dockerArgs = append(dockerArgs, words...)
+	}
+
+	filteredArgs := []string{"restart", "cpus", "memory", "memory-swap", "memory-reservation", "gpus"}
+	for _, filteredArg := range filteredArgs {
+		// re := regexp.MustCompile("--" + filteredArg + "=[0-9A-Za-z!\"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~]+ ")
+
+		var filteredDockerArgs []string
+		for _, dockerArg := range dockerArgs {
+			if !strings.HasPrefix(dockerArg, "--"+filteredArg+"=") {
+				filteredDockerArgs = append(filteredDockerArgs, dockerArg)
+			}
+		}
+
+		dockerArgs = filteredDockerArgs
+	}
+
+	dockerArgs = append(dockerArgs, "--label=dokku_phase_script="+phase)
+	dockerArgs = append(dockerArgs, "-v", cacheHostDir+":/cache")
+	if os.Getenv("DOKKU_TRACE") != "" {
+		dockerArgs = append(dockerArgs, "--env", "DOKKU_TRACE="+os.Getenv("DOKKU_TRACE"))
+	}
+
+	containerID, err := createdContainerID(appName, dockerArgs, image, script, phase)
+	if err != nil {
+		common.LogFail(fmt.Sprintf("Failed to create %s execution container: %s", phase, err.Error()))
+	}
+
+	if !waitForExecution(containerID) {
+		common.LogInfo2Quiet(fmt.Sprintf("Start of %s %s task (%s) output", appName, phase, containerID[0:9]))
+		common.LogVerboseQuietContainerLogs(containerID)
+		common.LogInfo2Quiet(fmt.Sprintf("End of %s %s task (%s) output", appName, phase, containerID[0:9]))
+		common.LogFail(fmt.Sprintf("Execution of %s task failed: %s", phase, command))
+	}
+
+	common.LogInfo2Quiet(fmt.Sprintf("Start of %s %s task (%s) output", appName, phase, containerID[0:9]))
+	common.LogVerboseQuietContainerLogs(containerID)
+	common.LogInfo2Quiet(fmt.Sprintf("End of %s %s task (%s) output", appName, phase, containerID[0:9]))
+
+	if phase != "predeploy" {
+		return nil
+	}
+
+	commitArgs := []string{"container", "commit"}
+	if !isHerokuishImage {
+		if dockerfileEntrypoint != "" {
+			commitArgs = append(commitArgs, "--change", dockerfileEntrypoint)
+		}
+
+		if dockerfileCommand != "" {
+			commitArgs = append(commitArgs, "--change", dockerfileCommand)
+		}
+	}
+
+	commitArgs = append(commitArgs, []string{
+		"--change",
+		"LABEL org.label-schema.schema-version=1.0",
+		"--change",
+		"LABEL org.label-schema.vendor=dokku",
+		"--change",
+		fmt.Sprintf("LABEL com.dokku.app-name=%s", appName),
+		"--change",
+		fmt.Sprintf("LABEL com.dokku.%s-phase=true", phase),
+	}...)
+	commitArgs = append(commitArgs, containerID, image)
+	containerCommitCmd := common.NewShellCmdWithArgs(
+		common.DockerBin(),
+		commitArgs...,
+	)
+	containerCommitCmd.ShowOutput = false
+	containerCommitCmd.Command.Stderr = os.Stderr
+	if !containerCommitCmd.Execute() {
+		common.LogFail(fmt.Sprintf("Commiting of '%s' to image failed: %s", phase, command))
+	}
+
+	return common.PlugnTrigger("scheduler-register-retired", []string{appName, containerID}...)
+}
+
+func getEntrypointFromImage(image string) (string, error) {
+	output, err := common.DockerInspect(image, "{{json .Config.Entrypoint}}")
+	if err != nil {
+		return "", err
+	}
+	if output == "null" {
+		return "", err
+	}
+
+	var entrypoint []string
+	if err = json.Unmarshal([]byte(output), &entrypoint); err != nil {
+		return "", err
+	}
+
+	if len(entrypoint) == 3 && entrypoint[0] == "/bin/sh" && entrypoint[1] == "-c" {
+		return fmt.Sprintf("ENTRYPOINT %s", entrypoint[2]), nil
+	}
+
+	serializedEntrypoint, err := json.Marshal(entrypoint)
+	return fmt.Sprintf("ENTRYPOINT %s", string(serializedEntrypoint)), err
+}
+
+func getCommandFromImage(image string) (string, error) {
+	output, err := common.DockerInspect(image, "{{json .Config.Cmd}}")
+	if err != nil {
+		return "", err
+	}
+	if output == "null" {
+		return "", err
+	}
+
+	var command []string
+	if err = json.Unmarshal([]byte(output), &command); err != nil {
+		return "", err
+	}
+
+	if len(command) == 3 && command[0] == "/bin/sh" && command[1] == "-c" {
+		return fmt.Sprintf("CMD %s", command[2]), nil
+	}
+
+	serializedEntrypoint, err := json.Marshal(command)
+	return fmt.Sprintf("CMD %s", string(serializedEntrypoint)), err
+}
+
+func waitForExecution(containerID string) bool {
+	containerStartCmd := common.NewShellCmdWithArgs(
+		common.DockerBin(),
+		"container",
+		"start",
+		containerID,
+	)
+	containerStartCmd.ShowOutput = false
+	containerStartCmd.Command.Stderr = os.Stderr
+	if !containerStartCmd.Execute() {
+		return false
+	}
+
+	containerWaitCmd := common.NewShellCmdWithArgs(
+		common.DockerBin(),
+		"container",
+		"wait",
+		containerID,
+	)
+
+	containerWaitCmd.ShowOutput = false
+	containerWaitCmd.Command.Stderr = os.Stderr
+	b, err := containerWaitCmd.Output()
+	if err != nil {
+		return false
+	}
+
+	containerExitCode := strings.TrimSpace(string(b[:]))
+	return containerExitCode == "0"
+}
+
+func createdContainerID(appName string, dockerArgs []string, image string, command []string, phase string) (string, error) {
+	runLabelArgs := fmt.Sprintf("--label=com.dokku.app-name=%s", appName)
+
+	arguments := strings.Split(common.MustGetEnv("DOKKU_GLOBAL_RUN_ARGS"), " ")
+	arguments = append(arguments, runLabelArgs)
+	arguments = append(arguments, dockerArgs...)
+
+	arguments = append([]string{"container", "create"}, arguments...)
+	arguments = append(arguments, image)
+	arguments = append(arguments, command...)
+
+	containerCreateCmd := common.NewShellCmdWithArgs(
+		common.DockerBin(),
+		arguments...,
+	)
+	var stderr bytes.Buffer
+	containerCreateCmd.ShowOutput = false
+	containerCreateCmd.Command.Stderr = &stderr
+
+	b, err := containerCreateCmd.Output()
+	if err != nil {
+		return "", errors.New(stderr.String())
+	}
+
+	containerID := strings.TrimSpace(string(b))
+	err = common.PlugnTrigger("post-container-create", []string{"app", appName, containerID, phase}...)
+	return containerID, err
+}
+
+func refreshAppJSON(appName string, image string) error {
+	baseDirectory := filepath.Join(common.MustGetEnv("DOKKU_LIB_ROOT"), "data", "app-json")
+	if !common.DirectoryExists(baseDirectory) {
+		return errors.New("Run 'dokku plugin:install' to ensure the correct directories exist")
+	}
+
+	directory := GetAppjsonDirectory(appName)
+	if !common.DirectoryExists(directory) {
+		if err := os.MkdirAll(directory, 0755); err != nil {
+			return err
+		}
+	}
+
+	appjsonPath := GetAppjsonPath(appName)
+	if common.FileExists(appjsonPath) {
+		if err := os.Remove(appjsonPath); err != nil {
+			return errors.New("Unable to remove previous app.json file")
+		}
+	}
+
+	common.CopyFromImage(appName, image, "app.json", appjsonPath)
+	return nil
+}
--- a/plugins/app-json/src/triggers/triggers.go
+++ b/plugins/app-json/src/triggers/triggers.go
@@ -6,7 +6,7 @@ import (
 	"os"
 	"strings"

-	"github.com/dokku/dokku/plugins/app-json"
+	appjson "github.com/dokku/dokku/plugins/app-json"
 	"github.com/dokku/dokku/plugins/common"
 )

@@ -18,6 +18,11 @@ func main() {

 	var err error
 	switch trigger {
+	case "install":
+		err = appjson.TriggerInstall()
+	case "post-delete":
+		appName := flag.Arg(0)
+		err = appjson.TriggerPostDelete(appName)
 	case "post-deploy":
 		appName := flag.Arg(0)
 		imageTag := flag.Arg(3)
--- a/plugins/app-json/triggers.go
+++ b/plugins/app-json/triggers.go
@@ -1,8 +1,47 @@
 package appjson

+import (
+	"os"
+	"path/filepath"
+
+	"github.com/dokku/dokku/plugins/common"
+)
+
+// TriggerInstall initializes app restart policies
+func TriggerInstall() error {
+	directory := filepath.Join(common.MustGetEnv("DOKKU_LIB_ROOT"), "data", "app-json")
+	if err := os.MkdirAll(directory, 0755); err != nil {
+		return err
+	}
+
+	if err := common.SetPermissions(directory, 0755); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// TriggerPostDelete destroys the app-json data for a given app container
+func TriggerPostDelete(appName string) error {
+	directory := filepath.Join(common.MustGetEnv("DOKKU_LIB_ROOT"), "data", "app-json", appName)
+	dataErr := os.RemoveAll(directory)
+	propertyErr := common.PropertyDestroy("app-json", appName)
+
+	if dataErr != nil {
+		return dataErr
+	}
+
+	return propertyErr
+}
+
 // TriggerPostDeploy is a trigger to execute the postdeploy deployment task
 func TriggerPostDeploy(appName string, imageTag string) error {
-	if err := executeScript(appName, imageTag, "postdeploy"); err != nil {
+	image, err := common.GetDeployingAppImageName(appName, imageTag, "")
+	if err != nil {
+		return err
+	}
+
+	if err := executeScript(appName, image, imageTag, "postdeploy"); err != nil {
 		return err
 	}
 	return nil
@@ -10,11 +49,20 @@ func TriggerPostDeploy(appName string, imageTag string) error {

 // TriggerPreDeploy is a trigger to execute predeploy and release deployment tasks
 func TriggerPreDeploy(appName string, imageTag string) error {
-	if err := executeScript(appName, imageTag, "predeploy"); err != nil {
+	image, err := common.GetDeployingAppImageName(appName, imageTag, "")
+	if err != nil {
 		return err
 	}

-	if err := executeScript(appName, imageTag, "release"); err != nil {
+	if err := refreshAppJSON(appName, image); err != nil {
+		return err
+	}
+
+	if err := executeScript(appName, image, imageTag, "predeploy"); err != nil {
+		return err
+	}
+
+	if err := executeScript(appName, image, imageTag, "release"); err != nil {
 		return err
 	}
 	return nil
--- a/plugins/cron/.gitignore
+++ b/plugins/cron/.gitignore
@@ -0,0 +1,6 @@
+/commands
+/subcommands/*
+/triggers/*
+/triggers
+/post-*
+/report
--- a/plugins/cron/Makefile
+++ b/plugins/cron/Makefile
@@ -0,0 +1,6 @@
+SUBCOMMANDS = subcommands/list subcommands/report
+TRIGGERS = triggers/post-delete triggers/post-deploy triggers/report
+BUILD = commands subcommands triggers
+PLUGIN_NAME = cron
+
+include ../../common.mk
--- a/plugins/cron/functions.go
+++ b/plugins/cron/functions.go
@@ -0,0 +1,152 @@
+package cron
+
+import (
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"html/template"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strings"
+
+	appjson "github.com/dokku/dokku/plugins/app-json"
+	"github.com/dokku/dokku/plugins/common"
+
+	cronparser "github.com/robfig/cron/v3"
+)
+
+type templateCommand struct {
+	ID       string
+	App      string
+	Command  string
+	Schedule string
+}
+
+func fetchCronEntries(appName string) ([]templateCommand, error) {
+	commands := []templateCommand{}
+	scheduler := common.GetAppScheduler(appName)
+	if scheduler != "docker-local" {
+		return commands, nil
+	}
+
+	appjsonPath := appjson.GetAppjsonPath(appName)
+	if !common.FileExists(appjsonPath) {
+		return commands, nil
+	}
+
+	b, err := ioutil.ReadFile(appjsonPath)
+	if err != nil {
+		return commands, fmt.Errorf("Cannot read app.json file for %s: %v", appName, err)
+	}
+
+	if strings.TrimSpace(string(b)) == "" {
+		return commands, nil
+	}
+
+	var appJSON appjson.AppJSON
+	if err = json.Unmarshal(b, &appJSON); err != nil {
+		return commands, fmt.Errorf("Cannot parse app.json for %s: %v", appName, err)
+	}
+
+	for _, c := range appJSON.Cron {
+		parser := cronparser.NewParser(cronparser.Minute | cronparser.Hour | cronparser.Dom | cronparser.Month | cronparser.Dow | cronparser.Descriptor)
+		_, err := parser.Parse(c.Schedule)
+		if err != nil {
+			return commands, err
+		}
+
+		commands = append(commands, templateCommand{
+			App:      appName,
+			Command:  c.Command,
+			Schedule: c.Schedule,
+			ID:       generateCommandID(appName, c),
+		})
+	}
+
+	return commands, nil
+}
+
+func writeCronEntries() error {
+	apps, err := common.DokkuApps()
+	if err != nil {
+		return nil
+	}
+
+	commands := []templateCommand{}
+	for _, appName := range apps {
+		scheduler := common.GetAppScheduler(appName)
+		if scheduler != "docker-local" {
+			continue
+		}
+
+		c, err := fetchCronEntries(appName)
+		if err != nil {
+			return err
+		}
+
+		commands = append(commands, c...)
+	}
+
+	if len(commands) == 0 {
+		if !common.FileExists("/var/spool/cron/crontabs/dokku") {
+			return nil
+		}
+
+		command := common.NewShellCmd("crontab -r -u dokku")
+		command.ShowOutput = false
+		out, err := command.CombinedOutput()
+		if err != nil {
+			return fmt.Errorf("Unable to remove schedule file: %v", out)
+		}
+	}
+
+	data := map[string]interface{}{
+		"Commands": commands,
+	}
+
+	t, err := getCronTemplate()
+	if err != nil {
+		return err
+	}
+
+	tmpFile, err := ioutil.TempFile(os.TempDir(), fmt.Sprintf("dokku-%s-%s", common.MustGetEnv("DOKKU_PID"), "CopyFromImage"))
+	if err != nil {
+		return fmt.Errorf("Cannot create temporary schedule file: %v", err)
+	}
+
+	defer tmpFile.Close()
+	defer os.Remove(tmpFile.Name())
+
+	if err := t.Execute(tmpFile, data); err != nil {
+		return fmt.Errorf("Unable to template out schedule file: %v", err)
+	}
+
+	command := common.NewShellCmd(fmt.Sprintf("crontab -u dokku %s", tmpFile.Name()))
+	command.ShowOutput = false
+	out, err := command.CombinedOutput()
+	if err != nil {
+		return fmt.Errorf("Unable to update schedule file: %v", out)
+	}
+
+	common.LogInfo1("Updated schedule file")
+
+	return nil
+}
+
+func getCronTemplate() (*template.Template, error) {
+	t := template.New("cron")
+
+	templatePath := filepath.Join(common.MustGetEnv("PLUGIN_ENABLED_PATH"), "cron", "templates", "cron.tmpl")
+	b, err := ioutil.ReadFile(templatePath)
+	if err != nil {
+		return t, fmt.Errorf("Cannot read template file: %v", err)
+	}
+
+	s := strings.TrimSpace(string(b))
+	return t.Parse(s)
+}
+
+func generateCommandID(appName string, c appjson.CronCommand) string {
+	return base64.StdEncoding.EncodeToString([]byte(appName + "===" + c.Command + "===" + c.Schedule))
+}
--- a/plugins/cron/go.mod
+++ b/plugins/cron/go.mod
@@ -0,0 +1,15 @@
+module github.com/dokku/dokku/plugins/cron
+
+go 1.15
+
+require (
+	github.com/dokku/dokku/plugins/app-json v0.0.0-00010101000000-000000000000
+	github.com/dokku/dokku/plugins/common v0.0.0-00010101000000-000000000000
+	github.com/robfig/cron/v3 v3.0.1
+	github.com/ryanuber/columnize v1.1.2-0.20190319233515-9e6335e58db3
+	github.com/spf13/pflag v1.0.5 // indirect
+)
+
+replace github.com/dokku/dokku/plugins/app-json => ../app-json
+
+replace github.com/dokku/dokku/plugins/common => ../common
--- a/plugins/cron/go.sum
+++ b/plugins/cron/go.sum
@@ -0,0 +1,15 @@
+github.com/codegangsta/inject v0.0.0-20150114235600-33e0aa1cb7c0 h1:sDMmm+q/3+BukdIpxwO365v/Rbspp2Nt5XntgQRXq8Q=
+github.com/codegangsta/inject v0.0.0-20150114235600-33e0aa1cb7c0/go.mod h1:4Zcjuz89kmFXt9morQgcfYZAYZ5n8WHjt81YYWIwtTM=
+github.com/codeskyblue/go-sh v0.0.0-20190412065543-76bd3d59ff27 h1:HHUr4P/aKh4quafGxDT9LDasjGdlGkzLbfmmrlng3kA=
+github.com/codeskyblue/go-sh v0.0.0-20190412065543-76bd3d59ff27/go.mod h1:VQx0hjo2oUeQkQUET7wRwradO6f+fN5jzXgB/zROxxE=
+github.com/kballard/go-shellquote v0.0.0-20180428030007-95032a82bc51 h1:Z9n2FFNUXsshfwJMBgNA0RU6/i7WVaAegv3PtuIHPMs=
+github.com/kballard/go-shellquote v0.0.0-20180428030007-95032a82bc51/go.mod h1:CzGEWj7cYgsdH8dAjBGEr58BoE7ScuLd+fwFZ44+/x8=
+github.com/robfig/cron v1.2.0 h1:ZjScXvvxeQ63Dbyxy76Fj3AT3Ut0aKsyd2/tl3DTMuQ=
+github.com/robfig/cron/v3 v3.0.1 h1:WdRxkvbJztn8LMz/QEvLN5sBU+xKpSqwwUO1Pjr4qDs=
+github.com/robfig/cron/v3 v3.0.1/go.mod h1:eQICP3HwyT7UooqI/z+Ov+PtYAWygg1TEWWzGIFLtro=
+github.com/ryanuber/columnize v1.1.2-0.20190319233515-9e6335e58db3 h1:utdYOikI1XjNtTFGCwSM6OmFJblU4ld4gACoJsbadJg=
+github.com/ryanuber/columnize v1.1.2-0.20190319233515-9e6335e58db3/go.mod h1:sm1tb6uqfes/u+d4ooFouqFdy9/2g9QGwK3SQygK0Ts=
+github.com/spf13/pflag v1.0.5 h1:iy+VFUOCP1a+8yFto/drg2CJ5u0yRoB7fZw3DKv/JXA=
+github.com/spf13/pflag v1.0.5/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
+golang.org/x/sync v0.0.0-20201207232520-09787c993a3a h1:DcqTD9SDLc+1P/r1EmRBwnVsrOwW+kk2vWf9n+1sGhs=
+golang.org/x/sync v0.0.0-20201207232520-09787c993a3a/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
--- a/plugins/cron/plugin.toml
+++ b/plugins/cron/plugin.toml
@@ -0,0 +1,4 @@
+[plugin]
+description = "dokku core cron plugin"
+version = "0.22.9"
+[plugin.config]
--- a/plugins/cron/report.go
+++ b/plugins/cron/report.go
@@ -0,0 +1,33 @@
+package cron
+
+import (
+	"strconv"
+
+	"github.com/dokku/dokku/plugins/common"
+)
+
+// ReportSingleApp is an internal function that displays the cron report for one or more apps
+func ReportSingleApp(appName, infoFlag string) error {
+	if err := common.VerifyAppName(appName); err != nil {
+		return err
+	}
+
+	flags := map[string]common.ReportFunc{
+		"--cron-task-count": reportTasks,
+	}
+
+	flagKeys := []string{}
+	for flagKey := range flags {
+		flagKeys = append(flagKeys, flagKey)
+	}
+
+	trimPrefix := false
+	uppercaseFirstCharacter := true
+	infoFlags := common.CollectReport(appName, infoFlag, flags)
+	return common.ReportSingleApp("cron", appName, infoFlag, infoFlags, flagKeys, trimPrefix, uppercaseFirstCharacter)
+}
+
+func reportTasks(appName string) string {
+	c, _ := fetchCronEntries(appName)
+	return strconv.Itoa(len(c))
+}
--- a/plugins/cron/src/commands/commands.go
+++ b/plugins/cron/src/commands/commands.go
@@ -0,0 +1,56 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"os"
+	"strconv"
+	"strings"
+
+	"github.com/dokku/dokku/plugins/common"
+)
+
+const (
+	helpHeader = `Usage: dokku cron[:COMMAND]
+
+Manage scheduled tasks
+
+Additional commands:`
+
+	helpContent = `
+    cron:list <app>, List scheduled tasks for an app
+    cron:report [<app>] [<flag>], Display report about an app
+`
+)
+
+func main() {
+	flag.Usage = usage
+	flag.Parse()
+
+	cmd := flag.Arg(0)
+	switch cmd {
+	case "cron", "cron:help":
+		usage()
+	case "help":
+		command := common.NewShellCmd(fmt.Sprintf("ps -o command= %d", os.Getppid()))
+		command.ShowOutput = false
+		output, err := command.Output()
+
+		if err == nil && strings.Contains(string(output), "--all") {
+			fmt.Println(helpContent)
+		} else {
+			fmt.Print("\n    cron, Manage scheduled cron tasks\n")
+		}
+	default:
+		dokkuNotImplementExitCode, err := strconv.Atoi(os.Getenv("DOKKU_NOT_IMPLEMENTED_EXIT"))
+		if err != nil {
+			fmt.Println("failed to retrieve DOKKU_NOT_IMPLEMENTED_EXIT environment variable")
+			dokkuNotImplementExitCode = 10
+		}
+		os.Exit(dokkuNotImplementExitCode)
+	}
+}
+
+func usage() {
+	common.CommandUsage(helpHeader, helpContent)
+}
--- a/plugins/cron/src/subcommands/subcommands.go
+++ b/plugins/cron/src/subcommands/subcommands.go
@@ -0,0 +1,41 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/dokku/dokku/plugins/common"
+	"github.com/dokku/dokku/plugins/cron"
+
+	flag "github.com/spf13/pflag"
+)
+
+// main entrypoint to all subcommands
+func main() {
+	parts := strings.Split(os.Args[0], "/")
+	subcommand := parts[len(parts)-1]
+
+	var err error
+	switch subcommand {
+	case "list":
+		args := flag.NewFlagSet("cron:list", flag.ExitOnError)
+		args.Parse(os.Args[2:])
+		appName := args.Arg(0)
+		err = cron.CommandList(appName)
+	case "report":
+		args := flag.NewFlagSet("cron:report", flag.ExitOnError)
+		osArgs, infoFlag, flagErr := common.ParseReportArgs("cron", os.Args[2:])
+		if flagErr == nil {
+			args.Parse(osArgs)
+			appName := args.Arg(0)
+			err = cron.CommandReport(appName, infoFlag)
+		}
+	default:
+		common.LogFail(fmt.Sprintf("Invalid plugin subcommand call: %s", subcommand))
+	}
+
+	if err != nil {
+		common.LogFail(err.Error())
+	}
+}
--- a/plugins/cron/src/triggers/triggers.go
+++ b/plugins/cron/src/triggers/triggers.go
@@ -0,0 +1,35 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/dokku/dokku/plugins/common"
+	cron "github.com/dokku/dokku/plugins/cron"
+)
+
+// main entrypoint to all triggers
+func main() {
+	parts := strings.Split(os.Args[0], "/")
+	trigger := parts[len(parts)-1]
+	flag.Parse()
+
+	var err error
+	switch trigger {
+	case "post-delete":
+		err = cron.TriggerPostDelete()
+	case "post-deploy":
+		err = cron.TriggerPostDeploy()
+	case "report":
+		appName := flag.Arg(0)
+		err = cron.ReportSingleApp(appName, "")
+	default:
+		common.LogFail(fmt.Sprintf("Invalid plugin trigger call: %s", trigger))
+	}
+
+	if err != nil {
+		common.LogFail(err.Error())
+	}
+}
--- a/plugins/cron/subcommands.go
+++ b/plugins/cron/subcommands.go
@@ -0,0 +1,47 @@
+package cron
+
+import (
+	"fmt"
+
+	"github.com/dokku/dokku/plugins/common"
+	"github.com/ryanuber/columnize"
+)
+
+// CommandList lists all scheduled cron tasks for a given app
+func CommandList(appName string) error {
+	if err := common.VerifyAppName(appName); err != nil {
+		return err
+	}
+
+	entries, err := fetchCronEntries(appName)
+	if err != nil {
+		return err
+	}
+
+	output := []string{"ID | Schedule | Command"}
+	for _, entry := range entries {
+		output = append(output, fmt.Sprintf("%s | %s | %s", entry.ID, entry.Schedule, entry.Command))
+	}
+	result := columnize.SimpleFormat(output)
+	fmt.Println(result)
+
+	return nil
+}
+
+// CommandReport displays a cron report for one or more apps
+func CommandReport(appName string, infoFlag string) error {
+	if len(appName) == 0 {
+		apps, err := common.DokkuApps()
+		if err != nil {
+			return err
+		}
+		for _, appName := range apps {
+			if err := ReportSingleApp(appName, infoFlag); err != nil {
+				return err
+			}
+		}
+		return nil
+	}
+
+	return ReportSingleApp(appName, infoFlag)
+}
--- a/plugins/cron/templates/cron.tmpl
+++ b/plugins/cron/templates/cron.tmpl
@@ -0,0 +1,6 @@
+PATH=/usr/local/bin:/usr/bin:/bin
+SHELL=/bin/bash
+
+{{ range $entry := .Commands -}}
+{{ $entry.Schedule }} dokku --rm run --cron-id {{ $entry.ID }} {{ $entry.App }} {{ $entry.Command }}
+{{ end -}}
--- a/plugins/cron/triggers.go
+++ b/plugins/cron/triggers.go
@@ -0,0 +1,11 @@
+package cron
+
+// TriggerPostDelete updates the cron entries for all apps
+func TriggerPostDelete() error {
+	return writeCronEntries()
+}
+
+// TriggerPostDeploy updates the cron entries for all apps
+func TriggerPostDeploy() error {
+	return writeCronEntries()
+}
--- a/plugins/scheduler-docker-local/scheduler-run
+++ b/plugins/scheduler-docker-local/scheduler-run
@@ -37,6 +37,10 @@ trigger-scheduler-docker-local-scheduler-run() {
  DOCKER_ARGS+=$(: | plugn trigger docker-args-process-run "$APP" "$IMAGE_SOURCE_TYPE" "$IMAGE_TAG")
  DOCKER_ARGS+=" -e DYNO=run.$DYNO_NUMBER --name $APP.run.$DYNO_NUMBER"

+  if [[ -n "$DOKKU_CRON_ID" ]]; then
+    DOCKER_ARGS+=" --label=com.dokku.cron-id=$DOKKU_CRON_ID"
+  fi
+
  declare -a ARG_ARRAY
  eval "ARG_ARRAY=($DOCKER_ARGS)"

--- a/tests/apps/python/task.py
+++ b/tests/apps/python/task.py
@@ -0,0 +1,5 @@
+def main(args):
+    print(args)
+
+if __name__ == '__main__':
+    main(sys.argv)
--- a/tests/unit/cron.bats
+++ b/tests/unit/cron.bats
@@ -0,0 +1,95 @@
+#!/usr/bin/env bats
+
+load test_helper
+
+setup() {
+  global_setup
+  create_app
+}
+
+teardown() {
+  destroy_app
+  global_teardown
+}
+
+@test "(cron) cron:help" {
+  run /bin/bash -c "dokku cron"
+  echo "output: $output"
+  echo "status: $status"
+  assert_output_contains "Manage scheduled cron tasks"
+  help_output="$output"
+
+  run /bin/bash -c "dokku cron:help"
+  echo "output: $output"
+  echo "status: $status"
+  assert_output_contains "Manage scheduled cron tasks"
+  assert_output "$help_output"
+}
+
+@test "(cron) invalid" {
+  run deploy_app python dokku@dokku.me:$TEST_APP template_cron_file_invalid
+  echo "output: $output"
+  echo "status: $status"
+  assert_failure
+
+  run deploy_app python dokku@dokku.me:$TEST_APP template_cron_file_invalid_schedule
+  echo "output: $output"
+  echo "status: $status"
+  assert_failure
+
+  run deploy_app python dokku@dokku.me:$TEST_APP template_cron_file_invalid_schedule_seconds
+  echo "output: $output"
+  echo "status: $status"
+  assert_failure
+}
+
+
+template_cron_file_invalid() {
+  local APP="$1"
+  local APP_REPO_DIR="$2"
+  [[ -z "$APP" ]] && local APP="$TEST_APP"
+  echo "injecting invalid cron app.json -> $APP_REPO_DIR/app.json"
+  cat <<EOF >"$APP_REPO_DIR/app.json"
+{
+  "cron": [
+    {
+      "key": "value"
+    }
+  ]
+}
+EOF
+}
+
+template_cron_file_invalid_schedule() {
+  local APP="$1"
+  local APP_REPO_DIR="$2"
+  [[ -z "$APP" ]] && local APP="$TEST_APP"
+  echo "injecting invalid cron app.json -> $APP_REPO_DIR/app.json"
+  cat <<EOF >"$APP_REPO_DIR/app.json"
+{
+  "cron": [
+    {
+      "command": "python task.py",
+      "schedule": "@nonstandard"
+    }
+  ]
+}
+EOF
+}
+
+template_cron_file_invalid_schedule_seconds() {
+  local APP="$1"
+  local APP_REPO_DIR="$2"
+  [[ -z "$APP" ]] && local APP="$TEST_APP"
+  echo "injecting invalid cron app.json -> $APP_REPO_DIR/app.json"
+  cat <<EOF >"$APP_REPO_DIR/app.json"
+{
+  "cron": [
+    {
+      "command": "python task.py",
+      "schedule": "0 5 * * * *"
+    }
+  ]
+}
+EOF
+}