add --strategy to choose the strategy to use

Signed-off-by: Victor Vieux <vieux@docker.com>

flags.go

@@ -0,0 +1,52 @@
+package main
+
+import "github.com/codegangsta/cli"
+
+var (
+	flDiscovery = cli.StringFlag{
+		Name:   "discovery",
+		Value:  "",
+		Usage:  "DiscoveryService to use [token://<token>, etcd://<ip1>,<ip2>/<path>, file://path/to/file]",
+		EnvVar: "SWARM_DISCOVERY",
+	}
+	flAddr = cli.StringFlag{
+		Name:   "addr",
+		Value:  "127.0.0.1:4243",
+		Usage:  "ip to advertise",
+		EnvVar: "SWARM_ADDR",
+	}
+	flHeartBeat = cli.IntFlag{
+		Name:  "heartbeat, hb",
+		Value: 25,
+		Usage: "time in second between each heartbeat",
+	}
+	flEnableCors = cli.BoolFlag{
+		Name:  "api-enable-cors, cors",
+		Usage: "enable CORS headers in the remote API",
+	}
+	flTls = cli.BoolFlag{
+		Name:  "tls",
+		Usage: "Use TLS; implied by --tlsverify=true",
+	}
+	flTlsCaCert = cli.StringFlag{
+		Name:  "tlscacert",
+		Usage: "Trust only remotes providing a certificate signed by the CA given here",
+	}
+	flTlsCert = cli.StringFlag{
+		Name:  "tlscert",
+		Usage: "Path to TLS certificate file",
+	}
+	flTlsKey = cli.StringFlag{
+		Name:  "tlskey",
+		Usage: "Path to TLS key file",
+	}
+	flTlsVerify = cli.BoolFlag{
+		Name:  "tlsverify",
+		Usage: "Use TLS and verify the remote",
+	}
+	flStrategy = cli.StringFlag{
+		Name:  "strategy",
+		Usage: "PlacementStrategy to use [binpacking, random]",
+		Value: "binpacking:0.05",
+	}
+)

main.go

@@ -36,49 +36,6 @@ func main() {
 		return nil
 	}
 
-	// flags
-	flDiscovery := cli.StringFlag{
-		Name:   "discovery",
-		Value:  "",
-		Usage:  "token://<token>, file://path/to/file",
-		EnvVar: "SWARM_DISCOVERY",
-	}
-	flAddr := cli.StringFlag{
-		Name:   "addr",
-		Value:  "127.0.0.1:4243",
-		Usage:  "ip to advertise",
-		EnvVar: "SWARM_ADDR",
-	}
-	flHeartBeat := cli.IntFlag{
-		Name:  "heartbeat, hb",
-		Value: 25,
-		Usage: "time in second between each heartbeat",
-	}
-	flEnableCors := cli.BoolFlag{
-		Name:  "api-enable-cors, cors",
-		Usage: "enable CORS headers in the remote API",
-	}
-	flTls := cli.BoolFlag{
-		Name:  "tls",
-		Usage: "Use TLS; implied by --tlsverify=true",
-	}
-	flTlsCaCert := cli.StringFlag{
-		Name:  "tlscacert",
-		Usage: "Trust only remotes providing a certificate signed by the CA given here",
-	}
-	flTlsCert := cli.StringFlag{
-		Name:  "tlscert",
-		Usage: "Path to TLS certificate file",
-	}
-	flTlsKey := cli.StringFlag{
-		Name:  "tlskey",
-		Usage: "Path to TLS key file",
-	}
-	flTlsVerify := cli.BoolFlag{
-		Name:  "tlsverify",
-		Usage: "Use TLS and verify the remote",
-	}
-
 	app.Commands = []cli.Command{
 		{
 			Name:      "create",
@@ -121,6 +78,7 @@ func main() {
 			ShortName: "m",
 			Usage:     "manage a docker cluster",
 			Flags: []cli.Flag{
+				flStrategy,
 				flDiscovery, flAddr, flHeartBeat,
 				flTls, flTlsCaCert, flTlsCert, flTlsKey, flTlsVerify,
 				flEnableCors},

manage.go

@@ -123,9 +123,13 @@ func manage(c *cli.Context) {
 		}
 	}()
 
-	s := scheduler.NewScheduler(
+	s, err := strategy.New(c.String("strategy"))
+	if err != nil {
+		log.Fatal(err)
+	}
+	sched := scheduler.NewScheduler(
 		cluster,
-		&strategy.BinPackingPlacementStrategy{OvercommitRatio: 0.05},
+		s,
 		[]filter.Filter{
 			&filter.HealthFilter{},
 			&filter.LabelFilter{},
@@ -133,5 +137,5 @@ func manage(c *cli.Context) {
 		},
 	)
 
-	log.Fatal(api.ListenAndServe(cluster, s, c.String("addr"), c.App.Version, c.Bool("cors"), tlsConfig))
+	log.Fatal(api.ListenAndServe(cluster, sched, c.String("addr"), c.App.Version, c.Bool("cors"), tlsConfig))
 }

scheduler/strategy/binpacking.go

@@ -3,6 +3,7 @@ package strategy
 import (
 	"errors"
 	"sort"
+	"strconv"
 
 	"github.com/docker/swarm/cluster"
 	"github.com/samalba/dockerclient"
@@ -16,6 +17,11 @@ type BinPackingPlacementStrategy struct {
 	OvercommitRatio float64
 }
 
+func (p *BinPackingPlacementStrategy) Initialize(opts string) (err error) {
+	p.OvercommitRatio, err = strconv.ParseFloat(opts, 64)
+	return err
+}
+
 func (p *BinPackingPlacementStrategy) PlaceContainer(config *dockerclient.ContainerConfig, nodes []*cluster.Node) (*cluster.Node, error) {
 	scores := scores{}
 

scheduler/strategy/random.go

@@ -9,14 +9,15 @@ import (
 	"github.com/samalba/dockerclient"
 )
 
-func init() {
-	rand.Seed(time.Now().UTC().UnixNano())
-}
-
 // Randomly place the container into the cluster.
 type RandomPlacementStrategy struct {
 }
 
+func (p *RandomPlacementStrategy) Initialize(_ string) error {
+	rand.Seed(time.Now().UTC().UnixNano())
+	return nil
+}
+
 func (p *RandomPlacementStrategy) PlaceContainer(config *dockerclient.ContainerConfig, nodes []*cluster.Node) (*cluster.Node, error) {
 	if size := len(nodes); size > 0 {
 		n := rand.Intn(len(nodes))

scheduler/strategy/strategy.go

@@ -1,12 +1,47 @@
 package strategy
 
 import (
+	"errors"
+	"strings"
+
+	log "github.com/Sirupsen/logrus"
 	"github.com/docker/swarm/cluster"
 	"github.com/samalba/dockerclient"
 )
 
 type PlacementStrategy interface {
+	Initialize(string) error
 	// Given a container configuration and a set of nodes, select the target
 	// node where the container should be scheduled.
 	PlaceContainer(config *dockerclient.ContainerConfig, nodes []*cluster.Node) (*cluster.Node, error)
 }
+
+var (
+	strategies      map[string]PlacementStrategy
+	ErrNotSupported = errors.New("strategy not supported")
+)
+
+func init() {
+	strategies = make(map[string]PlacementStrategy)
+	strategies["binpacking"] = &BinPackingPlacementStrategy{}
+	strategies["random"] = &RandomPlacementStrategy{}
+}
+
+func New(nameAndOpts string) (PlacementStrategy, error) {
+	var (
+		parts = strings.SplitN(nameAndOpts, ":", 2)
+		name  = parts[0]
+		opts  string
+	)
+	if len(parts) == 2 {
+		opts = parts[1]
+	}
+
+	if strategy, exists := strategies[name]; exists {
+		log.Debugf("Initialising %q strategy with %q", name, opts)
+		err := strategy.Initialize(opts)
+		return strategy, err
+	}
+
+	return nil, ErrNotSupported
+}