feat: add the ability to specify a custom mailto for all cron output

docs/development/plugin-triggers.md

@@ -549,18 +549,18 @@ echo "clock: some-command" >> Procfile
 popd &>/dev/null
 ```
 
-### `cron-write`
+### `cron-get-property`
 
-- Description: Force triggers writing out cron entries
+- Description: Return the value for an app's cron property
 - Invoked by:
-- Arguments:
+- Arguments: `$APP $KEY`
 - Example:
 
 ```shell
 #!/usr/bin/env bash
 
 set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
-source "$PLUGIN_CORE_AVAILABLE_PATH/common/functions"
+APP="$1"; PROPERTY="$2"
 
 # TODO
 ```
@@ -583,6 +583,22 @@ DOKKU_SCHEDULER="$1"
 # TODO
 ```
 
+### `cron-write`
+
+- Description: Force triggers writing out cron entries
+- Invoked by:
+- Arguments:
+- Example:
+
+```shell
+#!/usr/bin/env bash
+
+set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
+source "$PLUGIN_CORE_AVAILABLE_PATH/common/functions"
+
+# TODO
+```
+
 ### `dependencies`
 
 - Description: Used to install system-level dependencies.

docs/processes/scheduled-cron-tasks.md

@@ -46,10 +46,27 @@ When running scheduled cron tasks, there are a few items to be aware of:
 - Scheduled cron tasks are performed within the app environment available at runtime. If the app image does not exist, the command may fail to execute.
 - Schedules are performed on the hosting server's timezone, which is typically UTC.
 - At this time, only the `PATH` and `SHELL` environment variables are specified in the cron template.
+    - A `MAILTO` 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.
 
+#### Specifying a MAILTO value
+
+By default, cron tasks complete and do not perform any reporting. Users can specify a value for `MAILTO` via the global `mailto` cron property by using the `cron:set` command.
+
+```shell
+dokku cron:set --global mailto example@example.com
+```
+
+All output for individual cron runs will be sent to the specified email.
+
+Cron emails can be disabled by running the `cron:set` command for the global `mailto` property with no value.
+
+```shell
+dokku cron:set --global mailto
+```
+
 #### Listing Cron tasks
 
 Cron tasks for an app can be listed via the `cron:list` command. This command takes an `app` argument.

plugins/20_events/cron-get-property

@@ -0,0 +1 @@
+hook

plugins/cron/Makefile

@@ -1,5 +1,6 @@
 SUBCOMMANDS = subcommands/list subcommands/report subcommands/run
-BUILD = commands subcommands
+TRIGGERS = triggers/cron-get-property
+BUILD = commands subcommands triggers
 PLUGIN_NAME = cron
 
 include ../../common.mk

plugins/cron/cron.go

@@ -13,6 +13,18 @@ import (
 	cronparser "github.com/robfig/cron/v3"
 )
 
+var (
+	// DefaultProperties is a map of all valid network properties with corresponding default property values
+	DefaultProperties = map[string]string{
+		"mailto": "",
+	}
+
+	// GlobalProperties is a map of all valid global network properties
+	GlobalProperties = map[string]bool{
+		"mailto": true,
+	}
+)
+
 type TemplateCommand struct {
 	ID         string `json:"id"`
 	App        string `json:"app"`

plugins/cron/report.go

@@ -13,6 +13,7 @@ func ReportSingleApp(appName string, format string, infoFlag string) error {
 	}
 
 	flags := map[string]common.ReportFunc{
+		"--cron-mailto":     reportMailto,
 		"--cron-task-count": reportTasks,
 	}
 
@@ -27,6 +28,10 @@ func ReportSingleApp(appName string, format string, infoFlag string) error {
 	return common.ReportSingleApp("cron", appName, infoFlag, infoFlags, flagKeys, format, trimPrefix, uppercaseFirstCharacter)
 }
 
+func reportMailto(_ string) string {
+	return common.PropertyGet("cron", "--global", "mailto")
+}
+
 func reportTasks(appName string) string {
 	c, _ := FetchCronEntries(appName)
 	return strconv.Itoa(len(c))

plugins/cron/set.go

@@ -0,0 +1,11 @@
+package cron
+
+import "errors"
+
+func validateSetValue(appName string, key string, value string) error {
+	if key == "mailto" && appName != "--global" {
+		return errors.New("Property cannot be specified on a per-app basis")
+	}
+
+	return nil
+}

plugins/cron/src/triggers/triggers.go

@@ -0,0 +1,48 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/dokku/dokku/plugins/common"
+	"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 "cron-get-property":
+		appName := flag.Arg(0)
+		property := flag.Arg(1)
+		err = cron.TriggerCronGetProperty(appName, property)
+	case "install":
+		err = cron.TriggerInstall()
+	case "post-app-clone-setup":
+		oldAppName := flag.Arg(0)
+		newAppName := flag.Arg(1)
+		err = cron.TriggerPostAppCloneSetup(oldAppName, newAppName)
+	case "post-app-rename-setup":
+		oldAppName := flag.Arg(0)
+		newAppName := flag.Arg(1)
+		err = cron.TriggerPostAppRenameSetup(oldAppName, newAppName)
+	case "post-delete":
+		appName := flag.Arg(0)
+		err = cron.TriggerPostDelete(appName)
+	case "report":
+		appName := flag.Arg(0)
+		err = cron.ReportSingleApp(appName, "", "")
+	default:
+		err = fmt.Errorf("Invalid plugin trigger call: %s", trigger)
+	}
+
+	if err != nil {
+		common.LogFailWithError(err)
+	}
+}

plugins/cron/subcommands.go

@@ -112,3 +112,13 @@ func CommandRun(appName string, cronID string, detached bool) error {
 	args := append([]string{scheduler, appName, "0"}, fields...)
 	return common.PlugnTrigger("scheduler-run", args...)
 }
+
+// CommandSet set or clear a cron property for an app
+func CommandSet(appName string, property string, value string) error {
+	if err := validateSetValue(appName, property, value); err != nil {
+		return err
+	}
+
+	common.CommandPropertySet("cron", appName, property, value, DefaultProperties, GlobalProperties)
+	return common.PlugnTrigger("cron-write")
+}

plugins/cron/templates/cron.tmpl

@@ -1,3 +1,6 @@
+{{ if .Mailto -}}
+MAILTO={{ .Mailto }}
+{{ end -}}
 PATH=/usr/local/bin:/usr/bin:/bin
 SHELL=/bin/bash
 

plugins/cron/triggers.go

@@ -0,0 +1,55 @@
+package cron
+
+import (
+	"errors"
+	"fmt"
+
+	"github.com/dokku/dokku/plugins/common"
+)
+
+// TriggerCronGetProperty writes the cron key to stdout for a given app container
+func TriggerCronGetProperty(appName string, key string) error {
+	if key != "mailto" {
+		return errors.New("Invalid cron property specified")
+	}
+
+	fmt.Println(common.PropertyGet("cron", appName, key))
+	return nil
+}
+
+// TriggerInstall runs the install step for the cron plugin
+func TriggerInstall() error {
+	if err := common.PropertySetup("cron"); err != nil {
+		return fmt.Errorf("Unable to install the cron plugin: %s", err.Error())
+	}
+
+	return nil
+}
+
+// TriggerPostAppCloneSetup creates new cron files
+func TriggerPostAppCloneSetup(oldAppName string, newAppName string) error {
+	err := common.PropertyClone("cron", oldAppName, newAppName)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// TriggerPostAppRenameSetup renames cron files
+func TriggerPostAppRenameSetup(oldAppName string, newAppName string) error {
+	if err := common.PropertyClone("cron", oldAppName, newAppName); err != nil {
+		return err
+	}
+
+	if err := common.PropertyDestroy("cron", oldAppName); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// TriggerPostDelete destroys the cron property for a given app container
+func TriggerPostDelete(appName string) error {
+	return common.PropertyDestroy("cron", appName)
+}

plugins/scheduler-docker-local/functions.go

@@ -116,8 +116,11 @@ func writeCronEntries() error {
 		return deleteCrontab()
 	}
 
+	mailto, _ := common.PlugnTriggerOutputAsString("cron-get-property", []string{"--global", "mailto"}...)
+
 	data := map[string]interface{}{
 		"Commands": commands,
+		"Mailto":   mailto,
 	}
 
 	t, err := getCronTemplate()