resources: Simplify resource Converger and Startup code

This takes the Converged initialization and Startup patterns that are
common in all resources, and bakes it into the core engine. This way
resource writing is much more concise and there is less boilerplate!

resources/exec.go

@@ -25,7 +25,6 @@ import (
 	"log"
 	"os/exec"
 	"strings"
-	"time"
 
 	"github.com/purpleidea/mgmt/event"
 	"github.com/purpleidea/mgmt/util"
@@ -116,17 +115,7 @@ func (obj *ExecRes) Watch(processChan chan event.Event) error {
 	}
 	obj.SetWatching(true)
 	defer obj.SetWatching(false)
-	cuid := obj.converger.Register()
-	defer cuid.Unregister()
-
-	var startup bool
-	Startup := func(block bool) <-chan time.Time {
-		if block {
-			return nil // blocks forever
-			//return make(chan time.Time) // blocks forever
-		}
-		return time.After(time.Duration(500) * time.Millisecond) // 1/2 the resolution of converged timeout
-	}
+	cuid := obj.Converger() // get the converger uid used to report status
 
 	var send = false // send event?
 	var exit = false
@@ -169,6 +158,11 @@ func (obj *ExecRes) Watch(processChan chan event.Event) error {
 		bufioch, errch = obj.BufioChanScanner(scanner)
 	}
 
+	// notify engine that we're running
+	if err := obj.Running(processChan); err != nil {
+		return err // bubble up a NACK...
+	}
+
 	for {
 		obj.SetState(ResStateWatching) // reset
 		select {
@@ -199,15 +193,10 @@ func (obj *ExecRes) Watch(processChan chan event.Event) error {
 		case <-cuid.ConvergedTimer():
 			cuid.SetConverged(true) // converged!
 			continue
-
-		case <-Startup(startup):
-			cuid.SetConverged(false)
-			send = true
 		}
 
 		// do all our event sending all together to avoid duplicate msgs
 		if send {
-			startup = true // startup finished
 			send = false
 			// it is okay to invalidate the clean state on poke too
 			obj.StateOK(false) // something made state dirty