main: Libify mgmt with a golang API

This is an initial implementation of a possible golang API. In this
particular version, the *gconfig.GraphConfig data structures are
emitted, instead of possibly building a pgraph. As long as we can
represent any local graph as the data structure, then this is fine!

Is there a way to merge the gconfig Vertex and the pgraph Vertex?

examples/lib/libmgmt1.go

@@ -0,0 +1,110 @@
+// libmgmt example
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"os/signal"
+	"syscall"
+	"time"
+
+	"github.com/purpleidea/mgmt/gconfig"
+	mgmt "github.com/purpleidea/mgmt/mgmtmain"
+	"github.com/purpleidea/mgmt/resources"
+)
+
+func generateGraphConfig() *gconfig.GraphConfig {
+
+	n1, err := resources.NewNoopRes("noop1")
+	if err != nil {
+		return nil // error
+	}
+
+	gc := &gconfig.GraphConfig{
+		Graph: "libmgmt",
+		Resources: gconfig.Resources{ // must redefine anonymous struct :(
+			// in alphabetical order
+			Exec:  []*resources.ExecRes{},
+			File:  []*resources.FileRes{},
+			Msg:   []*resources.MsgRes{},
+			Noop:  []*resources.NoopRes{n1},
+			Pkg:   []*resources.PkgRes{},
+			Svc:   []*resources.SvcRes{},
+			Timer: []*resources.TimerRes{},
+			Virt:  []*resources.VirtRes{},
+		},
+		//Collector: []collectorResConfig{},
+		//Edges:     []Edge{},
+		Comment: "comment!",
+		//Hostname: "???",
+		//Remote: "???",
+	}
+	return gc
+}
+
+// Run runs an embedded mgmt server.
+func Run() error {
+
+	obj := &mgmt.Main{}
+	obj.Program = "mgmtlib" // TODO: set on compilation
+	obj.Version = "0.0.1"   // TODO: set on compilation
+	obj.TmpPrefix = true
+	obj.IdealClusterSize = -1
+	obj.ConvergedTimeout = -1
+	obj.Noop = true
+
+	obj.GAPI = generateGraphConfig // graph API function
+
+	if err := obj.Init(); err != nil {
+		return err
+	}
+
+	go func() {
+		for {
+			log.Printf("Generating new graph...")
+			obj.Switch(generateGraphConfig) // pass in function to run...
+
+			time.Sleep(15 * time.Second) // XXX: arbitrarily change graph every 30 seconds
+		}
+	}()
+
+	// 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!")
+}

gconfig/gconfig.go

@@ -41,33 +41,38 @@ type collectorResConfig struct {
 	Pattern string `yaml:"pattern"` // XXX: Not Implemented
 }
 
-type vertexConfig struct {
+// Vertex is the data structure of a vertex.
+type Vertex struct {
 	Kind string `yaml:"kind"`
 	Name string `yaml:"name"`
 }
 
-type edgeConfig struct {
-	Name string       `yaml:"name"`
-	From vertexConfig `yaml:"from"`
-	To   vertexConfig `yaml:"to"`
+// Edge is the data structure of an edge.
+type Edge struct {
+	Name string `yaml:"name"`
+	From Vertex `yaml:"from"`
+	To   Vertex `yaml:"to"`
+}
+
+// Resources is the data structure of the set of resources.
+type Resources struct {
+	// in alphabetical order
+	Exec  []*resources.ExecRes  `yaml:"exec"`
+	File  []*resources.FileRes  `yaml:"file"`
+	Msg   []*resources.MsgRes   `yaml:"msg"`
+	Noop  []*resources.NoopRes  `yaml:"noop"`
+	Pkg   []*resources.PkgRes   `yaml:"pkg"`
+	Svc   []*resources.SvcRes   `yaml:"svc"`
+	Timer []*resources.TimerRes `yaml:"timer"`
+	Virt  []*resources.VirtRes  `yaml:"virt"`
 }
 
 // GraphConfig is the data structure that describes a single graph to run.
 type GraphConfig struct {
-	Graph     string `yaml:"graph"`
-	Resources struct {
-		// in alphabetical order
-		Exec  []*resources.ExecRes  `yaml:"exec"`
-		File  []*resources.FileRes  `yaml:"file"`
-		Msg   []*resources.MsgRes   `yaml:"msg"`
-		Noop  []*resources.NoopRes  `yaml:"noop"`
-		Pkg   []*resources.PkgRes   `yaml:"pkg"`
-		Svc   []*resources.SvcRes   `yaml:"svc"`
-		Timer []*resources.TimerRes `yaml:"timer"`
-		Virt  []*resources.VirtRes  `yaml:"virt"`
-	} `yaml:"resources"`
+	Graph     string               `yaml:"graph"`
+	Resources Resources            `yaml:"resources"`
 	Collector []collectorResConfig `yaml:"collect"`
-	Edges     []edgeConfig         `yaml:"edges"`
+	Edges     []Edge               `yaml:"edges"`
 	Comment   string               `yaml:"comment"`
 	Hostname  string               `yaml:"hostname"` // uuid for the host
 	Remote    string               `yaml:"remote"`
@@ -152,9 +157,6 @@ func (c *GraphConfig) NewGraphFromConfig(g *pgraph.Graph, embdEtcd *etcd.EmbdEtc
 			// XXX: should we export based on a @@ prefix, or a metaparam
 			// like exported => true || exported => (host pattern)||(other pattern?)
 			if !strings.HasPrefix(res.GetName(), "@@") { // not exported resource
-				// XXX: we don't have a way of knowing if any of the
-				// metaparams are undefined, and as a result to set the
-				// defaults that we want! I hate the go yaml parser!!!
 				v := graph.GetVertexMatch(res)
 				if v == nil { // no match found
 					res.Init()

mgmtmain/main.go

@@ -49,10 +49,11 @@ type Main struct {
 
 	Hostname *string // hostname to use; nil if undefined
 
-	File       *string  // graph file to run; nil if undefined
-	Puppet     *string  // puppet mode to run; nil if undefined
-	PuppetConf string   // the path to an alternate puppet.conf file
-	Remotes    []string // list of remote graph definitions to run
+	File       *string                     // graph file to run; nil if undefined
+	Puppet     *string                     // puppet mode to run; nil if undefined
+	PuppetConf string                      // the path to an alternate puppet.conf file
+	GAPI       func() *gconfig.GraphConfig // graph API; nil if undefined
+	Remotes    []string                    // list of remote graph definitions to run
 
 	NoWatch          bool   // do not update graph on watched graph definition file changes
 	Noop             bool   // globally force all resources into no-op mode
@@ -80,12 +81,18 @@ type Main struct {
 	clientURLs       etcdtypes.URLs // processed client urls value
 	serverURLs       etcdtypes.URLs // processed server urls value
 	idealClusterSize uint16         // processed ideal cluster size value
-	exit             chan error     // exit signal
+
+	exit       chan error                       // exit signal
+	switchChan chan func() *gconfig.GraphConfig // graph switches
 }
 
 // Init initializes the main struct after it performs some validation.
 func (obj *Main) Init() error {
 
+	if obj.Program == "" || obj.Version == "" {
+		return fmt.Errorf("You must set the Program and Version strings!")
+	}
+
 	if obj.Prefix != nil && obj.TmpPrefix {
 		return fmt.Errorf("Choosing a prefix and the request for a tmp prefix is illogical!")
 	}
@@ -145,6 +152,7 @@ func (obj *Main) Init() error {
 	}
 
 	obj.exit = make(chan error)
+	obj.switchChan = make(chan func() *gconfig.GraphConfig)
 	return nil
 }
 
@@ -153,6 +161,14 @@ func (obj *Main) Exit(err error) {
 	obj.exit <- err // trigger an exit!
 }
 
+// Switch causes mgmt try to switch the currently running graph to a new one.
+// The function passed in will usually be called immediately, but it can also
+// happen after a delay, and more often than this Switch function is called!
+func (obj *Main) Switch(f func() *gconfig.GraphConfig) {
+	obj.switchChan <- f
+	// TODO: should we get an ACK() and pass back a return value ?
+}
+
 // Run is the main execution entrypoint to run mgmt.
 func (obj *Main) Run() error {
 
@@ -273,13 +289,14 @@ func (obj *Main) Run() error {
 	go func() {
 		startchan := make(chan struct{}) // start signal
 		go func() { startchan <- struct{}{} }()
-		var configchan chan error
-		var puppetchan <-chan time.Time
+		var configChan chan error
+		var puppetChan <-chan time.Time
+		var customFunc = obj.GAPI // default
 		if !obj.NoWatch && obj.File != nil {
-			configchan = recwatch.ConfigWatch(*obj.File)
+			configChan = recwatch.ConfigWatch(*obj.File)
 		} else if obj.Puppet != nil {
 			interval := puppet.PuppetInterval(obj.PuppetConf)
-			puppetchan = time.Tick(time.Duration(interval) * time.Second)
+			puppetChan = time.Tick(time.Duration(interval) * time.Second)
 		}
 		log.Println("Etcd: Starting...")
 		etcdchan := etcd.EtcdWatch(EmbdEtcd)
@@ -296,10 +313,14 @@ func (obj *Main) Run() error {
 				}
 				// everything else passes through to cause a compile!
 
-			case <-puppetchan:
+			case customFunc = <-obj.switchChan:
+				// handle a graph switch with a new custom function
+				obj.GAPI = customFunc
+
+			case <-puppetChan:
 				// nothing, just go on
 
-			case e := <-configchan:
+			case e := <-configChan:
 				if obj.NoWatch {
 					continue // not ready to read config
 				}
@@ -319,7 +340,10 @@ func (obj *Main) Run() error {
 				config = gconfig.ParseConfigFromFile(*obj.File)
 			} else if obj.Puppet != nil {
 				config = puppet.ParseConfigFromPuppet(*obj.Puppet, obj.PuppetConf)
+			} else if obj.GAPI != nil {
+				config = obj.GAPI()
 			}
+
 			if config == nil {
 				log.Printf("Config: Parse failure")
 				continue
@@ -337,7 +361,7 @@ func (obj *Main) Run() error {
 				G.Pause()         // sync
 			}
 
-			// build graph from yaml file on events (eg: from etcd)
+			// build graph from config struct on events, eg: etcd...
 			// we need the vertices to be paused to work on them
 			if newFullgraph, err := config.NewGraphFromConfig(fullGraph, EmbdEtcd, obj.Noop); err == nil { // keep references to all original elements
 				fullGraph = newFullgraph
@@ -420,7 +444,7 @@ func (obj *Main) Run() error {
 	// wait for etcd to be running before we remote in, which we do above!
 	go remotes.Run()
 
-	if obj.File == nil && obj.Puppet == nil {
+	if obj.File == nil && obj.Puppet == nil && obj.GAPI == nil {
 		converger.Start() // better start this for empty graphs
 	}
 	log.Println("Main: Running...")

test/test-headerfmt.sh

@@ -11,7 +11,7 @@ done < "$FILE"
 cd "${ROOT}"
 
 find_files() {
-	git ls-files | grep '\.go$'
+	git ls-files | grep '\.go$' | grep -v '^examples/'
 }
 
 bad_files=$(