resources: Implement Send -> Recv

This is a new design idea which I had. Whether it stays around or not is
up for debate. For now it's a rough POC.

The idea is that any resource can _produce_ data, and any resource can
_consume_ data. This is what we call send and recv. By linking the two
together, data can be passed directly between resources, which will
maximize code re-use, and allow for some interesting logical graphs.

For example, you might have an HTTP resource which puts its output in a
particular file. This avoids having to overload the HTTP resource with
all of the special behaviours of the File resource.

For our POC, I implemented a `password` resource which generates a
random string which can then be passed to a receiver such as a file. At
this point the password resource isn't recommended for sensitive
applications because it caches the password as plain text.

Still to do:
* Statically check all of the type matching before we run the graph
* Verify that our autogrouping works correctly around this feature
* Verify that appropriate edges exist between send->recv pairs
* Label the password as generated instead of storing the plain text
* Consider moving password logic from Init() to CheckApply()
* Consider combining multiple send values (list?) into a single receiver
* Consider intermediary transformation nodes for value combining

DOCUMENTATION.md

@@ -222,6 +222,7 @@ parameter with the [Noop](#Noop) resource.
 * [Msg](#Msg): Send log messages.
 * [Noop](#Noop): A simple resource that does nothing.
 * [Nspawn](#Nspawn): Manage systemd-machined nspawn containers.
+* [Password](#Password): Create random password strings.
 * [Pkg](#Pkg):  Manage system packages with PackageKit.
 * [Svc](#Svc): Manage system systemd services.
 * [Timer](#Timer): Manage system systemd services.
@@ -303,6 +304,10 @@ The noop resource does absolutely nothing. It does have some utility in testing
 
 The nspawn resource is used to manage systemd-machined style containers.
 
+###Password
+
+The password resource can generate a random string to be used as a password.
+
 ###Pkg
 
 The pkg resource is used to manage system packages. This resource works on many

examples/lib/libmgmt3.go

@@ -0,0 +1,192 @@
+// libmgmt example of send->recv
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"os/signal"
+	"sync"
+	"syscall"
+	"time"
+
+	"github.com/purpleidea/mgmt/gapi"
+	mgmt "github.com/purpleidea/mgmt/mgmtmain"
+	"github.com/purpleidea/mgmt/pgraph"
+	"github.com/purpleidea/mgmt/resources"
+)
+
+// MyGAPI implements the main GAPI interface.
+type MyGAPI struct {
+	Name     string // graph name
+	Interval uint   // refresh interval, 0 to never refresh
+
+	data        gapi.Data
+	initialized bool
+	closeChan   chan struct{}
+	wg          sync.WaitGroup // sync group for tunnel go routines
+}
+
+// NewMyGAPI creates a new MyGAPI struct and calls Init().
+func NewMyGAPI(data gapi.Data, name string, interval uint) (*MyGAPI, error) {
+	obj := &MyGAPI{
+		Name:     name,
+		Interval: interval,
+	}
+	return obj, obj.Init(data)
+}
+
+// Init initializes the MyGAPI struct.
+func (obj *MyGAPI) Init(data gapi.Data) error {
+	if obj.initialized {
+		return fmt.Errorf("Already initialized!")
+	}
+	if obj.Name == "" {
+		return fmt.Errorf("The graph name must be specified!")
+	}
+	obj.data = data // store for later
+	obj.closeChan = make(chan struct{})
+	obj.initialized = true
+	return nil
+}
+
+// Graph returns a current Graph.
+func (obj *MyGAPI) Graph() (*pgraph.Graph, error) {
+	if !obj.initialized {
+		return nil, fmt.Errorf("libmgmt: MyGAPI is not initialized")
+	}
+
+	g := pgraph.NewGraph(obj.Name)
+
+	p1 := &resources.PasswordRes{
+		BaseRes: resources.BaseRes{
+			Name: "password1",
+		},
+		Length: 8, // generated string will have this many characters
+	}
+	v1 := pgraph.NewVertex(p1)
+	g.AddVertex(v1)
+
+	f1 := &resources.FileRes{
+		BaseRes: resources.BaseRes{
+			Name: "file1",
+			// send->recv!
+			Recv: map[string]resources.Send{
+				"Content": resources.Send{Res: p1, Key: "Password"},
+			},
+		},
+		Path: "/tmp/mgmt/f1",
+		//Content:  p1.Password, // won't work
+		State: "present",
+	}
+
+	v2 := pgraph.NewVertex(f1)
+	g.AddVertex(v2)
+
+	g.AddEdge(v1, v2, pgraph.NewEdge("e1"))
+
+	//g, err := config.NewGraphFromConfig(obj.data.Hostname, obj.data.EmbdEtcd, obj.data.Noop)
+	return g, nil
+}
+
+// SwitchStream returns nil errors every time there could be a new graph.
+func (obj *MyGAPI) SwitchStream() chan error {
+	if obj.data.NoWatch || obj.Interval <= 0 {
+		return nil
+	}
+	ch := make(chan error)
+	obj.wg.Add(1)
+	go func() {
+		defer obj.wg.Done()
+		defer close(ch) // this will run before the obj.wg.Done()
+		if !obj.initialized {
+			ch <- fmt.Errorf("libmgmt: MyGAPI is not initialized")
+			return
+		}
+
+		// arbitrarily change graph every interval seconds
+		ticker := time.NewTicker(time.Duration(obj.Interval) * time.Second)
+		defer ticker.Stop()
+		for {
+			select {
+			case <-ticker.C:
+				log.Printf("libmgmt: Generating new graph...")
+				ch <- nil // trigger a run
+			case <-obj.closeChan:
+				return
+			}
+		}
+	}()
+	return ch
+}
+
+// Close shuts down the MyGAPI.
+func (obj *MyGAPI) Close() error {
+	if !obj.initialized {
+		return fmt.Errorf("libmgmt: MyGAPI is not initialized")
+	}
+	close(obj.closeChan)
+	obj.wg.Wait()
+	obj.initialized = false // closed = true
+	return nil
+}
+
+// Run runs an embedded mgmt server.
+func Run() error {
+
+	obj := &mgmt.Main{}
+	obj.Program = "libmgmt" // TODO: set on compilation
+	obj.Version = "0.0.1"   // TODO: set on compilation
+	obj.TmpPrefix = true
+	obj.IdealClusterSize = -1
+	obj.ConvergedTimeout = -1
+	obj.Noop = false // FIXME: careful!
+
+	obj.GAPI = &MyGAPI{ // graph API
+		Name:     "libmgmt", // TODO: set on compilation
+		Interval: 60 * 10,   // arbitrarily change graph every 15 seconds
+	}
+
+	if err := obj.Init(); err != nil {
+		return err
+	}
+
+	// install the exit signal handler
+	exit := make(chan struct{})
+	defer close(exit)
+	go func() {
+		signals := make(chan os.Signal, 1)
+		signal.Notify(signals, os.Interrupt) // catch ^C
+		//signal.Notify(signals, os.Kill) // catch signals
+		signal.Notify(signals, syscall.SIGTERM)
+
+		select {
+		case sig := <-signals: // any signal will do
+			if sig == os.Interrupt {
+				log.Println("Interrupted by ^C")
+				obj.Exit(nil)
+				return
+			}
+			log.Println("Interrupted by signal")
+			obj.Exit(fmt.Errorf("Killed by %v", sig))
+			return
+		case <-exit:
+			return
+		}
+	}()
+
+	if err := obj.Run(); err != nil {
+		return err
+	}
+	return nil
+}
+
+func main() {
+	log.Printf("Hello!")
+	if err := Run(); err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+		return
+	}
+	log.Printf("Goodbye!")
+}

mgmtmain/main.go

@@ -386,6 +386,7 @@ func (obj *Main) Run() error {
 			G.AutoEdges() // add autoedges; modifies the graph
 			G.AutoGroup() // run autogroup; modifies the graph
 			// TODO: do we want to do a transitive reduction?
+			// FIXME: run a type checker that verifies all the send->recv relationships
 
 			log.Printf("Graph: %v", G) // show graph
 			if obj.GraphvizFilter != "" {

pgraph/pgraph.go

@@ -659,6 +659,14 @@ func (g *Graph) Process(v *Vertex) error {
 		}
 
 		obj.SetState(resources.ResStateCheckApply)
+
+		// connect any senders to receivers and detect if values changed
+		if changed, err := obj.SendRecv(obj); err != nil {
+			return errwrap.Wrapf(err, "could not SendRecv in Process")
+		} else if changed {
+			obj.StateOK(false) // invalidate cache
+		}
+
 		// if this fails, don't UpdateTimestamp()
 		checkok, err := obj.CheckApply(!obj.Meta().Noop)
 		if checkok && err != nil { // should never return this way

resources/nspawn.go

@@ -198,6 +198,10 @@ func (obj *NspawnRes) CheckApply(apply bool) (checkok bool, err error) {
 		log.Printf("%s[%s]: CheckApply(%t)", obj.Kind(), obj.GetName(), apply)
 	}
 
+	if obj.isStateOK { // cache the state
+		return true, nil
+	}
+
 	// this resource depends on systemd ensure that it's running
 	if !systemdUtil.IsRunningSystemd() {
 		return false, errors.New("Systemd is not running.")

resources/password.go

@@ -0,0 +1,309 @@
+// Mgmt
+// Copyright (C) 2013-2016+ James Shubin and the project contributors
+// Written by James Shubin <james@shubin.ca> and the project contributors
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package resources
+
+import (
+	"crypto/rand"
+	"encoding/gob"
+	"fmt"
+	"log"
+	"math/big"
+	"os"
+	"path"
+	"strings"
+	"time"
+
+	"github.com/purpleidea/mgmt/event"
+
+	errwrap "github.com/pkg/errors"
+)
+
+func init() {
+	gob.Register(&PasswordRes{})
+}
+
+const (
+	alphabet = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
+	newline  = "\n" // something not in alphabet that TrimSpace can trim
+)
+
+// PasswordRes is a no-op resource that returns a random password string.
+type PasswordRes struct {
+	BaseRes `yaml:",inline"`
+	// FIXME: is uint16 too big?
+	Length   uint16  `yaml:"length"` // number of characters to return
+	Password *string // the generated password
+
+	path string // the path to local storage
+}
+
+// NewPasswordRes is a constructor for this resource. It also calls Init() for you.
+func NewPasswordRes(name string, length uint16) (*PasswordRes, error) {
+	obj := &PasswordRes{
+		BaseRes: BaseRes{
+			Name: name,
+		},
+		Length: length,
+	}
+	return obj, obj.Init()
+}
+
+func (obj *PasswordRes) read() (string, error) {
+	file, err := os.Open(obj.path) // open a handle to read the file
+	if err != nil {
+		return "", errwrap.Wrapf(err, "could not read password")
+	}
+	defer file.Close()
+	data := make([]byte, obj.Length+uint16(len(newline))) // data + newline
+	if _, err := file.Read(data); err != nil {
+		return "", errwrap.Wrapf(err, "could not read from file")
+	}
+	return strings.TrimSpace(string(data)), nil
+}
+
+func (obj *PasswordRes) write(password string) (int, error) {
+	file, err := os.Create(obj.path) // open a handle to create the file
+	if err != nil {
+		return -1, errwrap.Wrapf(err, "can't create file")
+	}
+	defer file.Close()
+	return file.Write([]byte(password + newline))
+}
+
+// generate generates a new password.
+func (obj *PasswordRes) generate() (string, error) {
+	max := len(alphabet) - 1 // last index
+	output := ""
+
+	// FIXME: have someone verify this is cryptographically secure & correct
+	for i := uint16(0); i < obj.Length; i++ {
+		big, err := rand.Int(rand.Reader, big.NewInt(int64(max)))
+		if err != nil {
+			return "", errwrap.Wrapf(err, "could not generate password")
+		}
+		ix := big.Int64()
+		output += string(alphabet[ix])
+	}
+
+	if output == "" { // safety against empty passwords
+		return "", fmt.Errorf("password is empty")
+	}
+
+	if uint16(len(output)) != obj.Length { // safety against weird bugs
+		return "", fmt.Errorf("password length is too short") // bug!
+	}
+
+	return output, nil
+}
+
+// check validates a stored password string
+func (obj *PasswordRes) check(value string) error {
+	length := uint16(len(value))
+	if length != obj.Length {
+		return fmt.Errorf("String length is not %d", obj.Length)
+	}
+Loop:
+	for i := uint16(0); i < length; i++ {
+		for j := 0; j < len(alphabet); j++ {
+			if value[i] == alphabet[j] {
+				continue Loop
+			}
+		}
+		// we couldn't find that character, so error!
+		return fmt.Errorf("Invalid character `%s`", string(value[i]))
+	}
+	return nil
+}
+
+// Init generates a new password for this resource if one was not provided. It
+// will save this into a local file. It will load it back in from previous runs.
+func (obj *PasswordRes) Init() error {
+	// XXX: eventually store a hash instead of the plain text! we might want
+	// to generate a new value on fresh run if the downstream resource needs
+	// an update (triggers a backpoke?) this is a POC for send/recv for now.
+	obj.BaseRes.kind = "Password" // must be set before using VarDir
+
+	dir, err := obj.VarDir("")
+	if err != nil {
+		return errwrap.Wrapf(err, "could not get VarDir in Init()")
+	}
+
+	obj.path = path.Join(dir, "password") // return a unique file
+	password := ""
+	if _, err := os.Stat(obj.path); err != nil { // probably doesn't exist
+		if !os.IsNotExist(err) {
+			return errwrap.Wrapf(err, "unknown stat error")
+		}
+
+		// generate password and store it in the file
+		if obj.Password != nil {
+			password = *obj.Password // reuse what we've got
+		} else {
+			var err error
+			if password, err = obj.generate(); err != nil { // generate one!
+				return errwrap.Wrapf(err, "could not init password")
+			}
+		}
+
+		// store it to disk
+		if _, err := obj.write(password); err != nil {
+			return errwrap.Wrapf(err, "can't write to file")
+		}
+
+	} else { // must exist already!
+
+		password, err := obj.read()
+		if err != nil {
+			return errwrap.Wrapf(err, "could not read password")
+		}
+		if err := obj.check(password); err != nil {
+			return errwrap.Wrapf(err, "check failed")
+		}
+
+		if p := obj.Password; p != nil && *p != password {
+			// stored password isn't consistent with memory
+			if _, err := obj.write(*p); err != nil {
+				return errwrap.Wrapf(err, "consistency overwrite failed")
+			}
+			password = *p // use the copy from the resource
+		}
+	}
+
+	obj.Password = &password // save in memory
+
+	return obj.BaseRes.Init() // call base init, b/c we're overriding
+}
+
+// Validate if the params passed in are valid data.
+// FIXME: where should this get called ?
+func (obj *PasswordRes) Validate() error {
+	return nil
+}
+
+// Watch is the primary listener for this resource and it outputs events.
+func (obj *PasswordRes) Watch(processChan chan event.Event) error {
+	if obj.IsWatching() {
+		return nil // TODO: should this be an 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
+	}
+
+	var send = false // send event?
+	var exit = false
+	for {
+		obj.SetState(ResStateWatching) // reset
+		select {
+		case event := <-obj.Events():
+			cuid.SetConverged(false)
+			// we avoid sending events on unpause
+			if exit, send = obj.ReadEvent(&event); exit {
+				return nil // exit
+			}
+
+		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
+			// only do this on certain types of events
+			//obj.isStateOK = false // something made state dirty
+			if exit, err := obj.DoSend(processChan, ""); exit || err != nil {
+				return err // we exit or bubble up a NACK...
+			}
+		}
+	}
+}
+
+// CheckApply method for Password resource. Does nothing, returns happy!
+func (obj *PasswordRes) CheckApply(apply bool) (checkok bool, err error) {
+	log.Printf("%s[%s]: CheckApply(%t)", obj.Kind(), obj.GetName(), apply)
+
+	return true, nil
+}
+
+// PasswordUID is the UID struct for PasswordRes.
+type PasswordUID struct {
+	BaseUID
+	name string
+}
+
+// AutoEdges returns the AutoEdge interface. In this case no autoedges are used.
+func (obj *PasswordRes) AutoEdges() AutoEdge {
+	return nil
+}
+
+// GetUIDs includes all params to make a unique identification of this object.
+// Most resources only return one, although some resources can return multiple.
+func (obj *PasswordRes) GetUIDs() []ResUID {
+	x := &PasswordUID{
+		BaseUID: BaseUID{name: obj.GetName(), kind: obj.Kind()},
+		name:    obj.Name,
+	}
+	return []ResUID{x}
+}
+
+// GroupCmp returns whether two resources can be grouped together or not.
+func (obj *PasswordRes) GroupCmp(r Res) bool {
+	_, ok := r.(*PasswordRes)
+	if !ok {
+		// NOTE: technically we could group a noop into any other
+		// resource, if that resource knew how to handle it, although,
+		// since the mechanics of inter-kind resource grouping are
+		// tricky, avoid doing this until there's a good reason.
+		return false
+	}
+	return true // noop resources can always be grouped together!
+}
+
+// Compare two resources and return if they are equivalent.
+func (obj *PasswordRes) Compare(res Res) bool {
+	switch res.(type) {
+	// we can only compare PasswordRes to others of the same resource
+	case *PasswordRes:
+		res := res.(*PasswordRes)
+		if !obj.BaseRes.Compare(res) { // call base Compare
+			return false
+		}
+
+		if obj.Name != res.Name {
+			return false
+		}
+	default:
+		return false
+	}
+	return true
+}

resources/resources.go

@@ -133,11 +133,14 @@ type Base interface {
 	DoSend(chan event.Event, string) (bool, error)
 	SendEvent(event.EventName, bool, bool) bool
 	ReadEvent(*event.Event) (bool, bool) // TODO: optional here?
-	GroupCmp(Res) bool                   // TODO: is there a better name for this?
-	GroupRes(Res) error                  // group resource (arg) into self
-	IsGrouped() bool                     // am I grouped?
-	SetGrouped(bool)                     // set grouped bool
-	GetGroup() []Res                     // return everyone grouped inside me
+	SendRecv(Res) (bool, error)          // send->recv data passing function
+	IsStateOK() bool
+	StateOK(b bool)
+	GroupCmp(Res) bool  // TODO: is there a better name for this?
+	GroupRes(Res) error // group resource (arg) into self
+	IsGrouped() bool    // am I grouped?
+	SetGrouped(bool)    // set grouped bool
+	GetGroup() []Res    // return everyone grouped inside me
 	SetGroup([]Res)
 	VarDir(string) (string, error)
 }
@@ -157,16 +160,19 @@ type Res interface {
 
 // BaseRes is the base struct that gets used in every resource.
 type BaseRes struct {
-	Name       string     `yaml:"name"`
-	MetaParams MetaParams `yaml:"meta"` // struct of all the metaparams
-	kind       string
-	events     chan event.Event
-	converger  converger.Converger // converged tracking
-	state      ResState
-	watching   bool  // is Watch() loop running ?
-	isStateOK  bool  // whether the state is okay based on events or not
-	isGrouped  bool  // am i contained within a group?
-	grouped    []Res // list of any grouped resources
+	Name       string          `yaml:"name"`
+	MetaParams MetaParams      `yaml:"meta"` // struct of all the metaparams
+	Recv       map[string]Send // mapping of key to receive on from value
+
+	kind      string
+	events    chan event.Event
+	converger converger.Converger // converged tracking
+	prefix    string              // base prefix for this resource
+	state     ResState
+	watching  bool  // is Watch() loop running ?
+	isStateOK bool  // whether the state is okay based on events or not
+	isGrouped bool  // am i contained within a group?
+	grouped   []Res // list of any grouped resources
 }
 
 // UIDExistsInUIDs wraps the IFF method when used with a list of UID's.
@@ -359,6 +365,16 @@ func (obj *BaseRes) ReadEvent(ev *event.Event) (exit, poke bool) {
 	return true, false // required to keep the stupid go compiler happy
 }
 
+// IsStateOK returns the cached state value.
+func (obj *BaseRes) IsStateOK() bool {
+	return obj.isStateOK
+}
+
+// StateOK sets the cached state value.
+func (obj *BaseRes) StateOK(b bool) {
+	obj.isStateOK = b
+}
+
 // GroupCmp compares two resources and decides if they're suitable for grouping
 // You'll probably want to override this method when implementing a resource...
 func (obj *BaseRes) GroupCmp(res Res) bool {

resources/sendrecv.go

@@ -0,0 +1,115 @@
+// Mgmt
+// Copyright (C) 2013-2016+ James Shubin and the project contributors
+// Written by James Shubin <james@shubin.ca> and the project contributors
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package resources
+
+import (
+	"fmt"
+	"log"
+	"reflect"
+
+	"github.com/purpleidea/mgmt/global"
+
+	multierr "github.com/hashicorp/go-multierror"
+	errwrap "github.com/pkg/errors"
+)
+
+// Send points to a value that a resource will send.
+type Send struct {
+	Res Res    // a handle to the resource which is sending a value
+	Key string // the key in the resource that we're sending
+}
+
+// SendRecv pulls in the sent values into the receive slots. It is called by the
+// receiver and must be given as input the full resource struct to receive on.
+func (obj *BaseRes) SendRecv(res Res) (bool, error) {
+	log.Printf("%s[%s]: SendRecv...", obj.Kind(), obj.GetName())
+	if global.DEBUG {
+		log.Printf("%s[%s]: SendRecv: Debug: %+v", obj.Kind(), obj.GetName(), obj.Recv)
+	}
+	var changed bool // did we update a value?
+	var err error
+	for k, v := range obj.Recv {
+		log.Printf("SendRecv: %s[%s].%s <- %s[%s].%s", obj.Kind(), obj.GetName(), k, v.Res.Kind(), v.Res.GetName(), v.Key)
+
+		// send
+		obj1 := reflect.Indirect(reflect.ValueOf(v.Res))
+		type1 := obj1.Type()
+		value1 := obj1.FieldByName(v.Key)
+		kind1 := value1.Kind()
+
+		// recv
+		obj2 := reflect.Indirect(reflect.ValueOf(res)) // pass in full struct
+		type2 := obj2.Type()
+		value2 := obj2.FieldByName(k)
+		kind2 := value2.Kind()
+
+		if global.DEBUG {
+			log.Printf("Send(%s) has %v: %v", type1, kind1, value1)
+			log.Printf("Recv(%s) has %v: %v", type2, kind2, value2)
+		}
+
+		// i think we probably want the same kind, at least for now...
+		if kind1 != kind2 {
+			e := fmt.Errorf("Kind mismatch between %s[%s]: %s and %s[%s]: %s", obj.Kind(), obj.GetName(), kind2, v.Res.Kind(), v.Res.GetName(), kind1)
+			err = multierr.Append(err, e) // list of errors
+			continue
+		}
+
+		// if the types don't match, we can't use send->recv
+		// TODO: do we want to relax this for string -> *string ?
+		if e := TypeCmp(value1, value2); e != nil {
+			e := errwrap.Wrapf(e, "Type mismatch between %s[%s] and %s[%s]", obj.Kind(), obj.GetName(), v.Res.Kind(), v.Res.GetName())
+			err = multierr.Append(err, e) // list of errors
+			continue
+		}
+
+		// if we can't set, then well this is pointless!
+		if !value2.CanSet() {
+			e := fmt.Errorf("Can't set %s[%s].%s", obj.Kind(), obj.GetName(), k)
+			err = multierr.Append(err, e) // list of errors
+			continue
+		}
+
+		// if we can't interface, we can't compare...
+		if !value1.CanInterface() || !value2.CanInterface() {
+			e := fmt.Errorf("Can't interface %s[%s].%s", obj.Kind(), obj.GetName(), k)
+			err = multierr.Append(err, e) // list of errors
+			continue
+		}
+
+		// if the values aren't equal, we're changing the receiver
+		if !reflect.DeepEqual(value1.Interface(), value2.Interface()) {
+			// TODO: can we catch the panics here in case they happen?
+			value2.Set(value1) // do it for all types that match
+			changed = true
+		}
+	}
+	return changed, err
+}
+
+// TypeCmp compares two reflect values to see if they are the same Kind. It can
+// look into a ptr Kind to see if the underlying pair of ptr's can TypeCmp too!
+func TypeCmp(a, b reflect.Value) error {
+	ta, tb := a.Type(), b.Type()
+	if ta != tb {
+		return fmt.Errorf("Type mismatch: %s != %s", ta, tb)
+	}
+	// NOTE: it seems we don't need to recurse into pointers to sub check!
+
+	return nil // identical Type()'s
+}

resources/svc.go

@@ -301,6 +301,7 @@ func (obj *SvcRes) CheckApply(apply bool) (checkok bool, err error) {
 	var startupOK = true // XXX: DETECT AND SET
 
 	if stateOK && startupOK {
+		obj.isStateOK = true
 		return true, nil // we are in the correct state
 	}
 
@@ -348,6 +349,7 @@ func (obj *SvcRes) CheckApply(apply bool) (checkok bool, err error) {
 
 	// XXX: also set enabled on boot
 
+	obj.isStateOK = true
 	return false, nil // success
 }
 

resources/timer.go

@@ -114,7 +114,7 @@ func (obj *TimerRes) Watch(processChan chan event.Event) error {
 		if send {
 			startup = true // startup finished
 			send = false
-			obj.isStateOK = false
+			//obj.isStateOK = false
 			if exit, err := obj.DoSend(processChan, "timer ticked"); exit || err != nil {
 				return err // we exit or bubble up a NACK...
 			}

yamlgraph/gconfig.go

@@ -62,6 +62,7 @@ type Resources struct {
 	Msg      []*resources.MsgRes      `yaml:"msg"`
 	Noop     []*resources.NoopRes     `yaml:"noop"`
 	Nspawn   []*resources.NspawnRes   `yaml:"nspawn"`
+	Password []*resources.PasswordRes `yaml:"password"`
 	Pkg      []*resources.PkgRes      `yaml:"pkg"`
 	Svc      []*resources.SvcRes      `yaml:"svc"`
 	Timer    []*resources.TimerRes    `yaml:"timer"`