engine: Resources package rewrite

This giant patch makes some much needed improvements to the code base.

* The engine has been rewritten and lives within engine/graph/
* All of the common interfaces and code now live in engine/
* All of the resources are in one package called engine/resources/
* The Res API can use different "traits" from engine/traits/
* The Res API has been simplified to hide many of the old internals
* The Watch & Process loops were previously inverted, but is now fixed
* The likelihood of package cycles has been reduced drastically
* And much, much more...

Unfortunately, some code had to be temporarily removed. The remote code
had to be taken out, as did the prometheus code. We hope to have these
back in new forms as soon as possible.

lang/gapi.go

@@ -19,13 +19,12 @@ package lang
 
 import (
 	"fmt"
-	"log"
 	"strings"
 	"sync"
 
+	"github.com/purpleidea/mgmt/engine"
 	"github.com/purpleidea/mgmt/gapi"
 	"github.com/purpleidea/mgmt/pgraph"
-	"github.com/purpleidea/mgmt/resources"
 
 	multierr "github.com/hashicorp/go-multierror"
 	errwrap "github.com/pkg/errors"
@@ -59,7 +58,7 @@ type GAPI struct {
 // should take the prefix of the registered name. On activation, if there are
 // any validation problems, you should return an error. If this was not
 // activated, then you should return a nil GAPI and a nil error.
-func (obj *GAPI) Cli(c *cli.Context, fs resources.Fs) (*gapi.Deploy, error) {
+func (obj *GAPI) Cli(c *cli.Context, fs engine.Fs) (*gapi.Deploy, error) {
 	if s := c.String(Name); c.IsSet(Name) {
 		if s == "" {
 			return nil, fmt.Errorf("input code is empty")
@@ -135,6 +134,10 @@ func (obj *GAPI) LangInit() error {
 		Hostname: obj.data.Hostname,
 		World:    obj.data.World,
 		Debug:    obj.data.Debug,
+		Logf: func(format string, v ...interface{}) {
+			// TODO: add the Name prefix in parent logger
+			obj.data.Logf(Name+": "+format, v...)
+		},
 	}
 	if err := obj.lang.Init(); err != nil {
 		return errwrap.Wrapf(err, "can't init the lang")
@@ -209,11 +212,11 @@ func (obj *GAPI) Next() chan gapi.Next {
 			case <-obj.closeChan:
 				return
 			}
-			log.Printf("%s: Generating new graph...", Name)
+			obj.data.Logf("generating new graph...")
 
 			// skip this to pass through the err if present
 			if langSwap && err == nil {
-				log.Printf("%s: Swap!", Name)
+				obj.data.Logf("swap!")
 				// run up to these three but fail on err
 				if e := obj.LangClose(); e != nil { // close any old lang
 					err = e // pass through the err
@@ -230,7 +233,29 @@ func (obj *GAPI) Next() chan gapi.Next {
 				} else {
 
 					if obj.data.NoStreamWatch { // TODO: do we want to allow this for the lang?
-						streamChan = nil
+						obj.data.Logf("warning: language will not stream")
+						// send only one event
+						limitChan := make(chan error)
+						obj.wg.Add(1)
+						go func() {
+							defer obj.wg.Done()
+							defer close(limitChan)
+							select {
+							// only one
+							case err, ok := <-obj.lang.Stream():
+								if !ok {
+									return
+								}
+								select {
+								case limitChan <- err:
+								case <-obj.closeChan:
+									return
+								}
+							case <-obj.closeChan:
+								return
+							}
+						}()
+						streamChan = limitChan
 					} else {
 						// stream for lang events
 						streamChan = obj.lang.Stream() // update stream