refactor: move host-crontab generation into cron plugin

Host-crontab generation for `app.json` cron tasks now lives in the `cron` plugin, gated by a new `scheduler-uses-host-cron` trigger that the `docker-local` scheduler answers true while self-managed schedulers such as `k3s` answer false. This lets any host-cron scheduler participate in normal `app.json` cron without coupling to `scheduler-docker-local` or duplicating the crontab writer, while the `k3s` scheduler continues to manage its own in-cluster cron jobs.

Closes #8862.

docs/deployment/schedulers/scheduler-management.md

@@ -122,7 +122,7 @@ At this time, the following dokku commands are used to implement a complete sche
 - `apps:clone`: handles app cloning
     - triggers: post-app-clone-setup
 - `cron`: generates cron tasks for the app
-    - triggers: scheduler-cron-write
+    - triggers: scheduler-uses-host-cron, scheduler-cron-write
 - `deploy`: deploys app proceses and checks the status of a deploy
     - triggers: scheduler-app-status, scheduler-deploy, scheduler-is-deployed, scheduler-logs-failed
 - `enter`: enters a running container

docs/development/plugin-triggers.md

@@ -2527,8 +2527,8 @@ DOKKU_SCHEDULER="$1"; APP="$2";
 > The scheduler plugin trigger apis are under development and may change
 > between minor releases until the 1.0 release.
 
-- Description: Force triggers writing out cron tasks. Arguments are optional.
-- Invoked by: `ps:start`, `ps:stop`, `cron:set`
+- Description: Force triggers writing out cron tasks. Arguments are optional. The `cron` plugin implements this for host-crontab schedulers (regenerating the whole `dokku` user crontab when the scheduler uses host cron or when no scheduler is given); self-managed schedulers such as `k3s` implement it to update their own cron backend.
+- Invoked by: `ps:start`, `ps:stop`, `cron:set`, `apps:destroy`
 - Arguments: `$DOKKU_SCHEDULER $APP`
 - Example:
 
@@ -2989,6 +2989,30 @@ DOKKU_SCHEDULER="$1"; APP="$2"; REMOVE_CONTAINERS="$3";
 - Arguments: `$SCHEDULER $ENTRY_NAME $IMAGE [-- $cmd...]`
 - Flags: `--interactive` (stdin is open), `--tty` (stdin is a terminal), `--as-user <uid>` (override `entry.Chown`).
 
+### `scheduler-uses-host-cron`
+
+> [!WARNING]
+> The scheduler plugin trigger apis are under development and may change
+> between minor releases until the 1.0 release.
+
+- Description: Reports whether the scheduler writes `app.json` cron tasks to the host `dokku` user crontab. Schedulers that use the host crontab (`docker-local`) echo `true`; schedulers that manage their own cron backend (`k3s`, which creates in-cluster CronJobs) echo `false`. The cron plugin reads this to decide which apps to include when regenerating the host crontab; a scheduler that does not implement the trigger is treated as `false`.
+- Invoked by: `cron`
+- Arguments: `$DOKKU_SCHEDULER`
+- Example:
+
+```shell
+#!/usr/bin/env bash
+
+set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
+DOKKU_SCHEDULER="$1";
+
+if [[ "$DOKKU_SCHEDULER" != "custom-scheduler" ]]; then
+  return
+fi
+
+echo "true"
+```
+
 ### `traefik-template-source`
 
 - Description: Retrieves an alternative template for the traefik compose config

docs/processes/scheduled-cron-tasks.md

@@ -57,8 +57,8 @@ When running scheduled cron tasks, there are a few items to be aware of:
     - A `MAILTO` value can be set via the `cron:set` command.
     - A `MAILFROM` value can be set via the `cron:set` command.
 - Each scheduled task is executed within a one-off `run` container, and thus inherit any docker-options specified for `run` containers. Resources are never shared between scheduled tasks.
-- Scheduled cron tasks are supported on a per-scheduler basis, and are currently only implemented by the `docker-local` scheduler.
-- Tasks for _all_ apps managed by the `docker-local` scheduler are written to a single crontab file owned by the `dokku` user. The `dokku` user's crontab should be considered reserved for this purpose.
+- Scheduled cron tasks are supported on a per-scheduler basis. Schedulers that use the host crontab - such as `docker-local` - have their `app.json` cron tasks written to the `dokku` user crontab, while schedulers that manage their own cron backend - such as `k3s` - schedule them natively.
+- Tasks for _all_ apps managed by a host-crontab scheduler such as `docker-local` are written to a single crontab file owned by the `dokku` user. The `dokku` user's crontab should be considered reserved for this purpose.
 - The `command` is tokenized and exec'd directly inside the container. Shell features such as `;`, `&&`, `|`, and `>` are _not_ interpreted. Commands that contain a bare shell operator are rejected when `app.json` is validated at deploy time, so a malformed cron command will fail the deploy rather than silently fail to run. If shell semantics are required, wrap the command explicitly, for example `"sh -c 'do-thing > /var/log/x.log'"`.
 
 

plugins/cron/.gitignore

@@ -7,4 +7,5 @@
 /install
 /post-*
 /report
+/scheduler-cron-write
 /scheduler-stop

plugins/cron/Makefile

@@ -1,5 +1,5 @@
 SUBCOMMANDS = subcommands/list subcommands/report subcommands/resume subcommands/run subcommands/set subcommands/suspend
-TRIGGERS = triggers/app-json-is-valid triggers/cron-get-property triggers/install triggers/post-app-clone-setup triggers/post-app-rename-setup triggers/post-delete triggers/scheduler-stop
+TRIGGERS = triggers/app-json-is-valid triggers/cron-get-property triggers/install triggers/post-app-clone-setup triggers/post-app-rename-setup triggers/post-delete triggers/post-deploy triggers/scheduler-cron-write triggers/scheduler-stop
 BUILD = commands subcommands triggers
 PLUGIN_NAME = cron
 

plugins/cron/crontab.go

@@ -0,0 +1,252 @@
+package cron
+
+import (
+	_ "embed"
+	"fmt"
+	"os"
+	"strings"
+	"text/template"
+
+	"github.com/dokku/dokku/plugins/common"
+	"golang.org/x/sync/errgroup"
+
+	base36 "github.com/multiformats/go-base36"
+)
+
+//go:embed templates/cron.tmpl
+var cronTemplate string
+
+// usesHostCron reports whether the given scheduler writes its cron tasks to the
+// host crontab (as opposed to managing its own cron backend). An empty scheduler
+// or an unimplemented scheduler-uses-host-cron trigger is treated as false.
+func usesHostCron(scheduler string) bool {
+	if scheduler == "" {
+		return false
+	}
+
+	results, _ := common.CallPlugnTrigger(common.PlugnTriggerInput{
+		Trigger: "scheduler-uses-host-cron",
+		Args:    []string{scheduler},
+	})
+	return results.StdoutContents() == "true"
+}
+
+// hostCronSchedulers returns a map keyed by every distinct scheduler seen across
+// the given apps plus the global scheduler, with a boolean value indicating
+// whether that scheduler uses the host crontab. Deduplicating up front avoids
+// redundant scheduler-uses-host-cron dispatches and any shared-cache race across
+// concurrent task collection.
+func hostCronSchedulers(appSchedulers []string) map[string]bool {
+	schedulers := map[string]bool{}
+	for _, scheduler := range append(appSchedulers, common.GetGlobalScheduler()) {
+		if scheduler == "" {
+			continue
+		}
+		if _, ok := schedulers[scheduler]; ok {
+			continue
+		}
+		schedulers[scheduler] = usesHostCron(scheduler)
+	}
+	return schedulers
+}
+
+// injectedCronTasks parses the tasks injected via the cron-entries trigger for a
+// given scheduler. Each entry is newline delimited in the form
+// $SCHEDULE;$COMMAND[;$LOGFILE].
+func injectedCronTasks(scheduler string) ([]CronTask, error) {
+	tasks := []CronTask{}
+	response, _ := common.CallPlugnTrigger(common.PlugnTriggerInput{
+		Trigger: "cron-entries",
+		Args:    []string{scheduler},
+	})
+	for _, line := range strings.Split(response.StdoutContents(), "\n") {
+		if strings.TrimSpace(line) == "" {
+			return []CronTask{}, nil
+		}
+
+		parts := strings.Split(line, ";")
+		if len(parts) != 2 && len(parts) != 3 {
+			return []CronTask{}, fmt.Errorf("Invalid injected cron task: %v", line)
+		}
+
+		id := base36.EncodeToStringLc([]byte(strings.Join(parts, ";;;")))
+		task := CronTask{
+			ID:          id,
+			Schedule:    parts[0],
+			AltCommand:  parts[1],
+			Maintenance: false,
+		}
+		if len(parts) == 3 {
+			task.LogFile = parts[2]
+		}
+		tasks = append(tasks, task)
+	}
+	return tasks, nil
+}
+
+// generateCronTasks returns all cron tasks that should be written to the host
+// crontab: the app.json cron tasks for every app whose scheduler uses the host
+// crontab, plus any tasks injected via the cron-entries trigger for each such
+// scheduler. Tasks in maintenance are omitted.
+func generateCronTasks() ([]CronTask, error) {
+	apps, _ := common.UnfilteredDokkuApps()
+
+	appSchedulers := make([]string, len(apps))
+	sg := new(errgroup.Group)
+	for i, appName := range apps {
+		i := i
+		appName := appName
+		sg.Go(func() error {
+			appSchedulers[i] = common.GetAppScheduler(appName)
+			return nil
+		})
+	}
+	if err := sg.Wait(); err != nil {
+		return []CronTask{}, err
+	}
+
+	hostCron := hostCronSchedulers(appSchedulers)
+
+	g := new(errgroup.Group)
+	results := make(chan []CronTask, len(apps)+len(hostCron))
+
+	for i, appName := range apps {
+		if !hostCron[appSchedulers[i]] {
+			continue
+		}
+		appName := appName
+		g.Go(func() error {
+			c, err := FetchCronTasks(FetchCronTasksInput{AppName: appName})
+			if err != nil {
+				results <- []CronTask{}
+				common.LogWarn(err.Error())
+				return nil
+			}
+
+			results <- c
+			return nil
+		})
+	}
+
+	for scheduler, isHostCron := range hostCron {
+		if !isHostCron {
+			continue
+		}
+		scheduler := scheduler
+		g.Go(func() error {
+			tasks, err := injectedCronTasks(scheduler)
+			if err != nil {
+				results <- []CronTask{}
+				return err
+			}
+
+			results <- tasks
+			return nil
+		})
+	}
+
+	err := g.Wait()
+	close(results)
+
+	tasks := []CronTask{}
+	if err != nil {
+		return tasks, err
+	}
+
+	for result := range results {
+		for _, task := range result {
+			if !task.Maintenance {
+				tasks = append(tasks, task)
+			}
+		}
+	}
+
+	return tasks, nil
+}
+
+// writeCronTab regenerates the dokku user crontab from every host-cron app. It
+// is always a full regeneration, so there is no clobbering when multiple
+// schedulers use the host crontab.
+func writeCronTab() error {
+	tasks, err := generateCronTasks()
+	if err != nil {
+		return err
+	}
+
+	if len(tasks) == 0 {
+		return deleteCrontab()
+	}
+
+	mailfrom := common.PropertyGetDefault("cron", "--global", "mailfrom", DefaultProperties["mailfrom"])
+	mailto := common.PropertyGetDefault("cron", "--global", "mailto", DefaultProperties["mailto"])
+
+	data := map[string]interface{}{
+		"Tasks":    tasks,
+		"Mailfrom": mailfrom,
+		"Mailto":   mailto,
+	}
+
+	t, err := getCronTemplate()
+	if err != nil {
+		return err
+	}
+
+	tmpFile, err := os.CreateTemp(os.TempDir(), fmt.Sprintf("dokku-%s-%s", common.MustGetEnv("DOKKU_PID"), "WriteCronTab"))
+	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)
+	}
+
+	result, err := common.CallExecCommand(common.ExecCommandInput{
+		Command: "crontab",
+		Args:    []string{"-u", "dokku", tmpFile.Name()},
+	})
+	if err != nil {
+		return fmt.Errorf("Unable to update schedule file: %w", err)
+	}
+	if result.ExitCode != 0 {
+		return fmt.Errorf("Unable to update schedule file: %s", result.StderrContents())
+	}
+
+	common.LogInfo1("Updated schedule file")
+
+	return nil
+}
+
+// deleteCrontab removes the dokku user crontab
+func deleteCrontab() error {
+	result, err := common.CallExecCommand(common.ExecCommandInput{
+		Command: "crontab",
+		Args:    []string{"-l", "-u", "dokku"},
+	})
+	if err != nil || result.ExitCode != 0 {
+		return nil
+	}
+
+	result, err = common.CallExecCommand(common.ExecCommandInput{
+		Command: "crontab",
+		Args:    []string{"-r", "-u", "dokku"},
+	})
+	if err != nil {
+		return fmt.Errorf("Unable to remove schedule file: %w", err)
+	}
+	if result.ExitCode != 0 {
+		return fmt.Errorf("Unable to remove schedule file: %s", result.StderrContents())
+	}
+
+	common.LogInfo1("Removed")
+	return nil
+}
+
+// getCronTemplate parses the embedded cron template
+func getCronTemplate() (*template.Template, error) {
+	t := template.New("cron")
+	s := strings.TrimSpace(cronTemplate)
+	return t.Parse(s)
+}

plugins/cron/go.mod

@@ -9,6 +9,7 @@ require (
 	github.com/robfig/cron/v3 v3.0.1
 	github.com/ryanuber/columnize v2.1.2+incompatible
 	github.com/spf13/pflag v1.0.10
+	golang.org/x/sync v0.22.0
 	mvdan.cc/sh/v3 v3.13.1
 )
 
@@ -28,7 +29,6 @@ require (
 	github.com/pkg/sftp v1.13.11 // indirect
 	github.com/tailscale/hujson v0.0.0-20250605163823-992244df8c5a // indirect
 	golang.org/x/crypto v0.54.0 // indirect
-	golang.org/x/sync v0.22.0 // indirect
 	golang.org/x/sys v0.47.0 // indirect
 	k8s.io/utils v0.0.0-20240102154912-e7106e64919e // indirect
 )

plugins/cron/src/triggers/triggers.go

@@ -44,9 +44,16 @@ func main() {
 	case "post-delete":
 		appName := flag.Arg(0)
 		err = cron.TriggerPostDelete(appName)
+	case "post-deploy":
+		appName := flag.Arg(0)
+		err = cron.TriggerPostDeploy(appName)
 	case "report":
 		appName := flag.Arg(0)
 		err = cron.ReportSingleApp(appName, "", "")
+	case "scheduler-cron-write":
+		scheduler := flag.Arg(0)
+		appName := flag.Arg(1)
+		err = cron.TriggerSchedulerCronWrite(scheduler, appName)
 	case "scheduler-stop":
 		scheduler := flag.Arg(0)
 		appName := flag.Arg(1)

plugins/cron/triggers.go

@@ -98,11 +98,43 @@ func TriggerPostDelete(appName string) error {
 	return nil
 }
 
-// TriggerSchedulerStop stops the scheduler for a given app container
-func TriggerSchedulerStop(scheduler string, appName string, removeContainers string) error {
-	if scheduler != "docker-local" {
+// TriggerPostDeploy regenerates the cron schedule for a given app after it is
+// deployed. Dispatching scheduler-cron-write lets the cron plugin regenerate the
+// host crontab for host-cron schedulers while self-managed schedulers update
+// their own backends.
+func TriggerPostDeploy(appName string) error {
+	scheduler := common.GetAppScheduler(appName)
+	_, err := common.CallPlugnTrigger(common.PlugnTriggerInput{
+		Trigger:     "scheduler-cron-write",
+		Args:        []string{scheduler, appName},
+		StreamStdio: true,
+	})
+	return err
+}
+
+// TriggerSchedulerCronWrite regenerates the host crontab when no scheduler is
+// given (the letsencrypt "all apps" path) or when the given scheduler uses the
+// host crontab. Self-managed schedulers implement their own scheduler-cron-write
+// trigger and are no-ops here.
+func TriggerSchedulerCronWrite(scheduler string, appName string) error {
+	if scheduler != "" && !usesHostCron(scheduler) {
 		return nil
 	}
 
-	return nil
+	return writeCronTab()
+}
+
+// TriggerSchedulerStop regenerates the host crontab for a host-cron app after
+// its processes are stopped
+func TriggerSchedulerStop(scheduler string, appName string, removeContainers string) error {
+	if !usesHostCron(scheduler) {
+		return nil
+	}
+
+	_, err := common.CallPlugnTrigger(common.PlugnTriggerInput{
+		Trigger:     "scheduler-cron-write",
+		Args:        []string{scheduler, appName},
+		StreamStdio: true,
+	})
+	return err
 }

plugins/scheduler-docker-local/.gitignore

@@ -3,6 +3,5 @@
 /cron-*
 /report
 /report-subcommand
-/scheduler-cron-write
 /scheduler-storage-exec
 /subcommands/report

plugins/scheduler-docker-local/Makefile

@@ -1,4 +1,4 @@
-TRIGGERS = triggers/report triggers/scheduler-cron-write triggers/scheduler-storage-exec
+TRIGGERS = triggers/report triggers/scheduler-storage-exec
 BUILD = report-subcommand triggers
 PLUGIN_NAME = scheduler-docker-local
 

plugins/scheduler-docker-local/functions.go

@@ -1,197 +0,0 @@
-package schedulerdockerlocal
-
-import (
-	"fmt"
-	"os"
-	"path/filepath"
-	"strings"
-	"text/template"
-
-	"github.com/dokku/dokku/plugins/common"
-	"github.com/dokku/dokku/plugins/cron"
-	"golang.org/x/sync/errgroup"
-
-	base36 "github.com/multiformats/go-base36"
-)
-
-func deleteCrontab() error {
-	result, err := common.CallExecCommand(common.ExecCommandInput{
-		Command: "crontab",
-		Args:    []string{"-l", "-u", "dokku"},
-	})
-	if err != nil || result.ExitCode != 0 {
-		return nil
-	}
-
-	result, err = common.CallExecCommand(common.ExecCommandInput{
-		Command: "crontab",
-		Args:    []string{"-r", "-u", "dokku"},
-	})
-	if err != nil {
-		return fmt.Errorf("Unable to remove schedule file: %w", err)
-	}
-	if result.ExitCode != 0 {
-		return fmt.Errorf("Unable to remove schedule file: %s", result.StderrContents())
-	}
-
-	common.LogInfo1("Removed")
-	return nil
-}
-
-func generateCronTasks() ([]cron.CronTask, error) {
-	apps, _ := common.UnfilteredDokkuApps()
-
-	g := new(errgroup.Group)
-	results := make(chan []cron.CronTask, len(apps)+1)
-	for _, appName := range apps {
-		appName := appName
-		g.Go(func() error {
-			scheduler := common.GetAppScheduler(appName)
-			if scheduler != "docker-local" {
-				results <- []cron.CronTask{}
-				return nil
-			}
-
-			c, err := cron.FetchCronTasks(cron.FetchCronTasksInput{AppName: appName})
-			if err != nil {
-				results <- []cron.CronTask{}
-				common.LogWarn(err.Error())
-				return nil
-			}
-
-			results <- c
-			return nil
-		})
-	}
-
-	g.Go(func() error {
-		tasks := []cron.CronTask{}
-		response, _ := common.CallPlugnTrigger(common.PlugnTriggerInput{
-			Trigger: "cron-entries",
-			Args:    []string{"docker-local"},
-		})
-		for _, line := range strings.Split(response.StdoutContents(), "\n") {
-			if strings.TrimSpace(line) == "" {
-				results <- []cron.CronTask{}
-				return nil
-			}
-
-			parts := strings.Split(line, ";")
-			if len(parts) != 2 && len(parts) != 3 {
-				results <- []cron.CronTask{}
-				return fmt.Errorf("Invalid injected cron task: %v", line)
-			}
-
-			id := base36.EncodeToStringLc([]byte(strings.Join(parts, ";;;")))
-			task := cron.CronTask{
-				ID:          id,
-				Schedule:    parts[0],
-				AltCommand:  parts[1],
-				Maintenance: false,
-			}
-			if len(parts) == 3 {
-				task.LogFile = parts[2]
-			}
-			tasks = append(tasks, task)
-		}
-		results <- tasks
-		return nil
-	})
-
-	err := g.Wait()
-	close(results)
-
-	tasks := []cron.CronTask{}
-	if err != nil {
-		return tasks, err
-	}
-
-	for result := range results {
-		for _, task := range result {
-			if !task.Maintenance {
-				tasks = append(tasks, task)
-			}
-		}
-	}
-
-	return tasks, nil
-}
-
-func writeCronTab(scheduler string) error {
-	// allow empty scheduler, which means all apps (used by letsencrypt)
-	if scheduler != "docker-local" && scheduler != "" {
-		return nil
-	}
-
-	tasks, err := generateCronTasks()
-	if err != nil {
-		return err
-	}
-
-	if len(tasks) == 0 {
-		return deleteCrontab()
-	}
-
-	resultfromResults, _ := common.CallPlugnTrigger(common.PlugnTriggerInput{
-		Trigger: "cron-get-property",
-		Args:    []string{"--global", "mailfrom"},
-	})
-	mailfrom := resultfromResults.StdoutContents()
-
-	mailtoResults, _ := common.CallPlugnTrigger(common.PlugnTriggerInput{
-		Trigger: "cron-get-property",
-		Args:    []string{"--global", "mailto"},
-	})
-	mailto := mailtoResults.StdoutContents()
-
-	data := map[string]interface{}{
-		"Tasks":    tasks,
-		"Mailfrom": mailfrom,
-		"Mailto":   mailto,
-	}
-
-	t, err := getCronTemplate()
-	if err != nil {
-		return err
-	}
-
-	tmpFile, err := os.CreateTemp(os.TempDir(), fmt.Sprintf("dokku-%s-%s", common.MustGetEnv("DOKKU_PID"), "WriteCronTab"))
-	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)
-	}
-
-	result, err := common.CallExecCommand(common.ExecCommandInput{
-		Command: "crontab",
-		Args:    []string{"-u", "dokku", tmpFile.Name()},
-	})
-	if err != nil {
-		return fmt.Errorf("Unable to update schedule file: %w", err)
-	}
-	if result.ExitCode != 0 {
-		return fmt.Errorf("Unable to update schedule file: %s", result.StderrContents())
-	}
-
-	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 := os.ReadFile(templatePath)
-	if err != nil {
-		return t, fmt.Errorf("Cannot read template file: %v", err)
-	}
-
-	s := strings.TrimSpace(string(b))
-	return t.Parse(s)
-}

plugins/scheduler-docker-local/go.mod

@@ -4,21 +4,16 @@ go 1.26.2
 
 require (
 	github.com/dokku/dokku/plugins/common v0.0.0-00010101000000-000000000000
-	github.com/dokku/dokku/plugins/cron v0.0.0-00010101000000-000000000000
 	github.com/dokku/dokku/plugins/storage v0.0.0-00010101000000-000000000000
-	github.com/multiformats/go-base36 v0.2.0
 	github.com/spf13/pflag v1.0.10
-	golang.org/x/sync v0.22.0
 )
 
 require (
 	github.com/alexellis/go-execute/v2 v2.2.1 // indirect
-	github.com/dokku/dokku/plugins/app-json v0.0.0-00010101000000-000000000000 // indirect
 	github.com/dokku/dokku/plugins/docker-options v0.0.0-00010101000000-000000000000 // indirect
 	github.com/fatih/color v1.19.0 // indirect
 	github.com/hashicorp/errwrap v1.0.0 // indirect
 	github.com/hashicorp/go-multierror v1.1.1 // indirect
-	github.com/kballard/go-shellquote v0.0.0-20180428030007-95032a82bc51 // indirect
 	github.com/kr/fs v0.1.0 // indirect
 	github.com/mattn/go-colorable v0.1.14 // indirect
 	github.com/mattn/go-isatty v0.0.23 // indirect
@@ -27,21 +22,15 @@ require (
 	github.com/otiai10/mint v1.6.3 // indirect
 	github.com/pkg/errors v0.9.1 // indirect
 	github.com/pkg/sftp v1.13.11 // indirect
-	github.com/robfig/cron/v3 v3.0.1 // indirect
 	github.com/ryanuber/columnize v2.1.2+incompatible // indirect
-	github.com/tailscale/hujson v0.0.0-20250605163823-992244df8c5a // indirect
 	golang.org/x/crypto v0.54.0 // indirect
+	golang.org/x/sync v0.22.0 // indirect
 	golang.org/x/sys v0.47.0 // indirect
-	k8s.io/utils v0.0.0-20240102154912-e7106e64919e // indirect
 	mvdan.cc/sh/v3 v3.13.1 // indirect
 )
 
-replace github.com/dokku/dokku/plugins/app-json => ../app-json
-
 replace github.com/dokku/dokku/plugins/common => ../common
 
-replace github.com/dokku/dokku/plugins/cron => ../cron
-
 replace github.com/dokku/dokku/plugins/storage => ../storage
 
 replace github.com/dokku/dokku/plugins/docker-options => ../docker-options

plugins/scheduler-docker-local/go.sum

@@ -12,8 +12,6 @@ github.com/hashicorp/errwrap v1.0.0 h1:hLrqtEDnRye3+sgx6z4qVLNuviH3MR5aQ0ykNJa/U
 github.com/hashicorp/errwrap v1.0.0/go.mod h1:YH+1FKiLXxHSkmPseP+kNlulaMuP3n2brvKWEqk/Jc4=
 github.com/hashicorp/go-multierror v1.1.1 h1:H5DkEtf6CXdFp0N0Em5UCwQpXMWke8IA0+lD48awMYo=
 github.com/hashicorp/go-multierror v1.1.1/go.mod h1:iw975J/qwKPdAO1clOe2L8331t/9/fmwbPZ6JB6eMoM=
-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/kr/fs v0.1.0 h1:Jskdu9ieNAYnjxsi0LbQp1ulIKZV1LAFgK1tWhpZgl8=
 github.com/kr/fs v0.1.0/go.mod h1:FFnZGqtBN9Gxj7eW1uZ42v5BccTP0vu6NEaFoC2HwRg=
 github.com/kr/pretty v0.3.1 h1:flRD4NNwYAUpkphVc1HcthR4KEIFJ65n8Mw5qdRn3LE=
@@ -26,8 +24,6 @@ github.com/mattn/go-isatty v0.0.23 h1:cYwCQTQf3HB6xUC+BtyCLZNr7IzbOmoZbmssVNzSyi
 github.com/mattn/go-isatty v0.0.23/go.mod h1:nMCL3Zebbrt45jsMDgnfIwz6ydEQApk5oEI3HqDio6A=
 github.com/melbahja/goph v1.5.2 h1:2eoR45SLF3LyM6tnIhnpjakvXTjtQMJqOK/mp1PYojM=
 github.com/melbahja/goph v1.5.2/go.mod h1:T+5uoB1PDP6EeK2qXerf5gRh7b6IF8u37GK2ckEi9FU=
-github.com/multiformats/go-base36 v0.2.0 h1:lFsAbNOGeKtuKozrtBsAkSVhv1p9D0/qedU9rQyccr0=
-github.com/multiformats/go-base36 v0.2.0/go.mod h1:qvnKE++v+2MWCfePClUEjE78Z7P2a1UV0xHgWc0hkp4=
 github.com/onsi/gomega v1.42.1 h1:iN1rCUX+44NZ1Dc97MPoeFYbFR0vh8zxoxMFwKdyZ6I=
 github.com/onsi/gomega v1.42.1/go.mod h1:REff/hsDsodHoKlWsP2mAPhu1+5/6hVYNf9rIEBpeSg=
 github.com/otiai10/copy v1.14.1 h1:5/7E6qsUMBaH5AnQ0sSLzzTg1oTECmcCmT6lvF45Na8=
@@ -40,8 +36,6 @@ github.com/pkg/sftp v1.13.11 h1:0N92SLTB8JqASJB14ZLHHzFnBV8mG9zw4K7jghEFWuE=
 github.com/pkg/sftp v1.13.11/go.mod h1:uNkH9roSXglNJqM+glJJi+TQXQUm0fXFWqCFmT8hsN0=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
-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/rogpeppe/go-internal v1.14.1 h1:UQB4HGPB6osV0SQTLymcB4TgvyWu6ZyliaW0tI/otEQ=
 github.com/rogpeppe/go-internal v1.14.1/go.mod h1:MaRKkUm5W0goXpeCfT7UZI6fk/L7L7so1lCWt35ZSgc=
 github.com/ryanuber/columnize v2.1.2+incompatible h1:C89EOx/XBWwIXl8wm8OPJBd7kPF25UfsK2X7Ph/zCAk=
@@ -50,8 +44,6 @@ github.com/spf13/pflag v1.0.10 h1:4EBh2KAYBwaONj6b2Ye1GiHfwjqyROoF4RwYO+vPwFk=
 github.com/spf13/pflag v1.0.10/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
 github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
 github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
-github.com/tailscale/hujson v0.0.0-20250605163823-992244df8c5a h1:a6TNDN9CgG+cYjaeN8l2mc4kSz2iMiCDQxPEyltUV/I=
-github.com/tailscale/hujson v0.0.0-20250605163823-992244df8c5a/go.mod h1:EbW0wDK/qEUYI0A5bqq0C2kF8JTQwWONmGDBbzsxxHo=
 go.yaml.in/yaml/v3 v3.0.4 h1:tfq32ie2Jv2UxXFdLJdh3jXuOzWiL1fo0bu/FbuKpbc=
 go.yaml.in/yaml/v3 v3.0.4/go.mod h1:DhzuOOF2ATzADvBadXxruRBLzYTpT36CKvDb3+aBEFg=
 golang.org/x/crypto v0.54.0 h1:YLIA59K4fiNzHzjnZt2tUJQjQtUWfWbeHBqKtk3eScw=
@@ -68,7 +60,5 @@ golang.org/x/text v0.40.0 h1:Ub2Z6/xjgF1WrYQz2nuITOEegKFtiIy+rieRJ5lHZKs=
 golang.org/x/text v0.40.0/go.mod h1:hpnzDAfGV753zIKo+wk3u1bVKCGPbrnF7+7LBF/UHVY=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
-k8s.io/utils v0.0.0-20240102154912-e7106e64919e h1:eQ/4ljkx21sObifjzXwlPKpdGLrCfRziVtos3ofG/sQ=
-k8s.io/utils v0.0.0-20240102154912-e7106e64919e/go.mod h1:OLgZIPagt7ERELqWJFomSt595RzquPNLL48iOWgYOg0=
 mvdan.cc/sh/v3 v3.13.1 h1:DP3TfgZhDkT7lerUdnp6PTGKyxxzz6T+cOlY/xEvfWk=
 mvdan.cc/sh/v3 v3.13.1/go.mod h1:lXJ8SexMvEVcHCoDvAGLZgFJ9Wsm2sulmoNEXGhYZD0=

plugins/scheduler-docker-local/post-deploy

@@ -1,15 +0,0 @@
-#!/usr/bin/env bash
-set -eo pipefail
-source "$PLUGIN_CORE_AVAILABLE_PATH/common/functions"
-[[ $DOKKU_TRACE ]] && set -x
-
-trigger-scheduler-docker-local-post-deploy() {
-  declare desc="scheduler-docker-local post-deploy plugin trigger"
-  declare trigger="post-deploy"
-  declare APP="$1"
-
-  local DOKKU_SCHEDULER="$(get_app_scheduler "$APP")"
-  plugn trigger scheduler-cron-write "$DOKKU_SCHEDULER" "$APP"
-}
-
-trigger-scheduler-docker-local-post-deploy "$@"

plugins/scheduler-docker-local/scheduler-stop

@@ -50,8 +50,6 @@ trigger-scheduler-docker-local-scheduler-stop() {
       "$DOCKER_BIN" container rm --force $DOKKU_APP_CIDS &>/dev/null || true
     fi
   fi
-
-  plugn trigger scheduler-cron-write "$DOKKU_SCHEDULER" "$APP"
 }
 
 trigger-scheduler-docker-local-scheduler-stop "$@"

plugins/scheduler-docker-local/scheduler-uses-host-cron

@@ -0,0 +1,17 @@
+#!/usr/bin/env bash
+set -eo pipefail
+[[ $DOKKU_TRACE ]] && set -x
+
+trigger-scheduler-docker-local-scheduler-uses-host-cron() {
+  declare desc="reports whether the scheduler writes cron tasks to the host crontab"
+  declare trigger="scheduler-uses-host-cron"
+  declare DOKKU_SCHEDULER="$1"
+
+  if [[ "$DOKKU_SCHEDULER" != "docker-local" ]]; then
+    return
+  fi
+
+  echo "true"
+}
+
+trigger-scheduler-docker-local-scheduler-uses-host-cron "$@"

plugins/scheduler-docker-local/src/triggers/triggers.go

@@ -23,9 +23,6 @@ func main() {
 
 	var err error
 	switch trigger {
-	case "scheduler-cron-write":
-		scheduler := flag.Arg(0)
-		err = schedulerdockerlocal.TriggerSchedulerCronWrite(scheduler)
 	case "scheduler-storage-exec":
 		args := flag.Args()
 		if len(args) < 3 {

plugins/scheduler-docker-local/triggers.go

@@ -1,6 +0,0 @@
-package schedulerdockerlocal
-
-// TriggerSchedulerCronWrite force updates the cron file for all apps
-func TriggerSchedulerCronWrite(scheduler string) error {
-	return writeCronTab(scheduler)
-}

plugins/scheduler-k3s/Makefile

@@ -1,5 +1,5 @@
 SUBCOMMANDS = subcommands/annotations:set subcommands/annotations:report subcommands/autoscaling-auth:set subcommands/autoscaling-auth:report subcommands/charts:report subcommands/charts:set subcommands/cluster:add subcommands/cluster:list subcommands/cluster:remove subcommands/ensure-charts subcommands/initialize subcommands/labels:set subcommands/labels:report subcommands/preview subcommands/profiles:add subcommands/profiles:list subcommands/profiles:remove subcommands/report subcommands/set subcommands/show-kubeconfig subcommands/uninstall
-TRIGGERS = triggers/core-post-deploy triggers/core-post-extract triggers/install triggers/post-app-clone-setup triggers/post-app-rename-setup triggers/post-certs-update triggers/post-certs-remove triggers/post-create triggers/post-delete triggers/report triggers/scheduler-app-status triggers/scheduler-deploy triggers/scheduler-enter triggers/scheduler-is-deployed triggers/scheduler-logs triggers/scheduler-proxy-config triggers/scheduler-proxy-logs triggers/scheduler-post-delete triggers/scheduler-run triggers/scheduler-run-list triggers/scheduler-stop triggers/scheduler-cron-write triggers/storage-create triggers/storage-destroy triggers/storage-status triggers/scheduler-storage-exec
+TRIGGERS = triggers/core-post-deploy triggers/core-post-extract triggers/install triggers/post-app-clone-setup triggers/post-app-rename-setup triggers/post-certs-update triggers/post-certs-remove triggers/post-create triggers/post-delete triggers/report triggers/scheduler-app-status triggers/scheduler-deploy triggers/scheduler-enter triggers/scheduler-is-deployed triggers/scheduler-logs triggers/scheduler-proxy-config triggers/scheduler-proxy-logs triggers/scheduler-post-delete triggers/scheduler-run triggers/scheduler-run-list triggers/scheduler-stop triggers/scheduler-cron-write triggers/scheduler-uses-host-cron triggers/storage-create triggers/storage-destroy triggers/storage-status triggers/scheduler-storage-exec
 BUILD = commands subcommands triggers
 PLUGIN_NAME = scheduler-k3s
 

plugins/scheduler-k3s/src/triggers/triggers.go

@@ -86,6 +86,9 @@ func main() {
 		scheduler := flag.Arg(0)
 		appName := flag.Arg(1)
 		err = scheduler_k3s.TriggerSchedulerIsDeployed(scheduler, appName)
+	case "scheduler-uses-host-cron":
+		scheduler := flag.Arg(0)
+		err = scheduler_k3s.TriggerSchedulerUsesHostCron(scheduler)
 	case "scheduler-logs":
 		var tail bool
 		var quiet bool

plugins/scheduler-k3s/triggers.go

@@ -637,6 +637,17 @@ func TriggerSchedulerIsDeployed(scheduler string, appName string) error {
 	return fmt.Errorf("App %s is not deployed", appName)
 }
 
+// TriggerSchedulerUsesHostCron reports that the k3s scheduler does not use the
+// host crontab; it manages its own in-cluster CronJobs
+func TriggerSchedulerUsesHostCron(scheduler string) error {
+	if scheduler != "k3s" {
+		return nil
+	}
+
+	fmt.Println("false")
+	return nil
+}
+
 // TriggerSchedulerEnter enters a container for a given application
 func TriggerSchedulerEnter(scheduler string, appName string, processType string, podName string, args []string) error {
 	if scheduler != "k3s" {

plugins/scheduler-null/scheduler-uses-host-cron

@@ -0,0 +1,17 @@
+#!/usr/bin/env bash
+set -eo pipefail
+[[ $DOKKU_TRACE ]] && set -x
+
+trigger-scheduler-null-scheduler-uses-host-cron() {
+  declare desc="reports whether the scheduler writes cron tasks to the host crontab"
+  declare trigger="scheduler-uses-host-cron"
+  declare DOKKU_SCHEDULER="$1"
+
+  if [[ "$DOKKU_SCHEDULER" != "null" ]]; then
+    return
+  fi
+
+  echo "false"
+}
+
+trigger-scheduler-null-scheduler-uses-host-cron "$@"

tests/unit/cron.bats

@@ -18,6 +18,10 @@ EOF
 
 teardown() {
   rm -rf /var/lib/dokku/plugins/available/cron-entries /var/lib/dokku/plugins/enabled/cron-entries
+  # restore the default scheduler before destroy: a k3s-scheduled app cannot be
+  # torn down cleanly without a cluster, and would otherwise leak into the next
+  # test's cleanup_apps
+  dokku scheduler:set "$TEST_APP" selected docker-local 2>/dev/null || true
   destroy_app
   global_teardown
 }
@@ -43,6 +47,32 @@ teardown() {
   assert_failure
 }
 
+@test "(cron) scheduler-uses-host-cron" {
+  run /bin/bash -c "dokku plugin:trigger scheduler-uses-host-cron docker-local"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+  assert_output "true"
+
+  run /bin/bash -c "dokku plugin:trigger scheduler-uses-host-cron k3s"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+  assert_output "false"
+
+  run /bin/bash -c "dokku plugin:trigger scheduler-uses-host-cron null"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+  assert_output "false"
+
+  run /bin/bash -c "dokku plugin:trigger scheduler-uses-host-cron bogus-scheduler"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+  assert_output ""
+}
+
 @test "(cron) invalid [missing-keys]" {
   run deploy_app python dokku@$DOKKU_DOMAIN:$TEST_APP template_cron_file_invalid
   echo "output: $output"
@@ -406,6 +436,39 @@ teardown() {
   assert_failure
 }
 
+@test "(cron) k3s-scheduled app skips host crontab" {
+  run deploy_app python dokku@$DOKKU_DOMAIN:$TEST_APP template_cron_file_valid_single
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+
+  cron_id="$(dokku cron:list $TEST_APP --format json | jq -r '.[0].id')"
+
+  run /bin/bash -c "cat /var/spool/cron/crontabs/dokku"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+  assert_output_contains "dokku cron:run $TEST_APP $cron_id"
+
+  # switch the app to a scheduler that manages its own cron backend
+  run /bin/bash -c "dokku scheduler:set $TEST_APP selected k3s"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+
+  # regenerating the host crontab must now skip the k3s app's tasks, leaving
+  # no host-cron tasks and therefore no crontab file
+  run /bin/bash -c "dokku plugin:trigger scheduler-cron-write"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+
+  run /bin/bash -c "cat /var/spool/cron/crontabs/dokku"
+  echo "output: $output"
+  echo "status: $status"
+  assert_failure
+}
+
 @test "(cron) cron:list --format json" {
   run deploy_app python dokku@$DOKKU_DOMAIN:$TEST_APP template_cron_file_valid
   echo "output: $output"