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.

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)
+}

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())
+	}
+}

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())
+	}
+}