refactor code: move filter/ and strategy/ out of scheduler and create a simple

scheduler interface.

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

README.md

@@ -80,7 +80,7 @@ other discovery services.
 
 ## Advanced Scheduling
 
-See [filters](scheduler/filter) and [strategies](scheduler/strategy) to learn
+See [filters](filter) and [strategies](strategy) to learn
 more about advanced scheduling.
 
 ## TLS

api/api.go

@@ -16,8 +16,8 @@ import (
 	dockerfilters "github.com/docker/docker/pkg/parsers/filters"
 	"github.com/docker/docker/pkg/units"
 	"github.com/docker/swarm/cluster"
+	"github.com/docker/swarm/filter"
 	"github.com/docker/swarm/scheduler"
-	"github.com/docker/swarm/scheduler/filter"
 	"github.com/docker/swarm/version"
 	"github.com/gorilla/mux"
 	"github.com/samalba/dockerclient"
@@ -27,7 +27,7 @@ const APIVERSION = "1.16"
 
 type context struct {
 	cluster       *cluster.Cluster
-	scheduler     *scheduler.Scheduler
+	scheduler     scheduler.Scheduler
 	eventsHandler *eventsHandler
 	debug         bool
 	tlsConfig     *tls.Config

api/api_test.go

@@ -12,7 +12,7 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
-func serveRequest(c *cluster.Cluster, s *scheduler.Scheduler, w http.ResponseWriter, req *http.Request) error {
+func serveRequest(c *cluster.Cluster, s scheduler.Scheduler, w http.ResponseWriter, req *http.Request) error {
 	context := &context{
 		cluster:   c,
 		scheduler: s,

api/server.go

@@ -29,7 +29,7 @@ func newListener(proto, addr string, tlsConfig *tls.Config) (net.Listener, error
 	return l, nil
 }
 
-func ListenAndServe(c *cluster.Cluster, s *scheduler.Scheduler, hosts []string, enableCors bool, tlsConfig *tls.Config) error {
+func ListenAndServe(c *cluster.Cluster, s scheduler.Scheduler, hosts []string, enableCors bool, tlsConfig *tls.Config) error {
 	context := &context{
 		cluster:       c,
 		scheduler:     s,

flags.go

@@ -94,4 +94,9 @@ var (
 		Usage: "filter to use [constraint, affinity, health, port, dependency]",
 		Value: &flFilterValue,
 	}
+	flScheduler = cli.StringFlag{
+		Name:  "scheduler, s",
+		Usage: "scheduler to use [builtin, mesos]",
+		Value: "builtin",
+	}
 )

manage.go

@@ -12,10 +12,10 @@ import (
 	"github.com/docker/swarm/api"
 	"github.com/docker/swarm/cluster"
 	"github.com/docker/swarm/discovery"
+	"github.com/docker/swarm/filter"
 	"github.com/docker/swarm/scheduler"
-	"github.com/docker/swarm/scheduler/filter"
-	"github.com/docker/swarm/scheduler/strategy"
 	"github.com/docker/swarm/state"
+	"github.com/docker/swarm/strategy"
 )
 
 type logHandler struct {
@@ -137,12 +137,16 @@ func manage(c *cli.Context) {
 		go d.Watch(cluster.UpdateNodes)
 	}()
 
-	sched := scheduler.NewScheduler(
+	sched, err := scheduler.New(c.String("scheduler"),
 		cluster,
 		s,
 		fs,
 	)
 
+	if err != nil {
+		log.Fatal(err)
+	}
+
 	// see https://github.com/codegangsta/cli/issues/160
 	hosts := c.StringSlice("host")
 	if c.IsSet("host") || c.IsSet("H") {

scheduler/builtin/builtin.go

@@ -0,0 +1,63 @@
+package builtin
+
+import (
+	"sync"
+
+	"github.com/docker/swarm/cluster"
+	"github.com/docker/swarm/filter"
+	"github.com/docker/swarm/strategy"
+	"github.com/samalba/dockerclient"
+)
+
+type BuiltinScheduler struct {
+	sync.Mutex
+
+	cluster  *cluster.Cluster
+	strategy strategy.PlacementStrategy
+	filters  []filter.Filter
+}
+
+func (s *BuiltinScheduler) Initialize(cluster *cluster.Cluster, strategy strategy.PlacementStrategy, filters []filter.Filter) {
+	s.cluster = cluster
+	s.strategy = strategy
+	s.filters = filters
+}
+
+// Find a nice home for our container.
+func (s *BuiltinScheduler) selectNodeForContainer(config *dockerclient.ContainerConfig) (*cluster.Node, error) {
+	candidates := s.cluster.Nodes()
+
+	accepted, err := filter.ApplyFilters(s.filters, config, candidates)
+	if err != nil {
+		return nil, err
+	}
+
+	return s.strategy.PlaceContainer(config, accepted)
+}
+
+// Schedule a brand new container into the cluster.
+func (s *BuiltinScheduler) CreateContainer(config *dockerclient.ContainerConfig, name string) (*cluster.Container, error) {
+	/*Disable for now
+	if config.Memory == 0 || config.CpuShares == 0 {
+		return nil, fmt.Errorf("Creating containers in clustering mode requires resource constraints (-c and -m) to be set")
+	}
+	*/
+
+	s.Lock()
+	defer s.Unlock()
+
+	node, err := s.selectNodeForContainer(config)
+	if err != nil {
+		return nil, err
+	}
+	return s.cluster.DeployContainer(node, config, name)
+}
+
+// Remove a container from the cluster. Containers should always be destroyed
+// through the scheduler to guarantee atomicity.
+func (s *BuiltinScheduler) RemoveContainer(container *cluster.Container, force bool) error {
+	s.Lock()
+	defer s.Unlock()
+
+	return s.cluster.DestroyContainer(container, force)
+}

scheduler/scheduler.go

@@ -1,65 +1,38 @@
 package scheduler
 
 import (
-	"sync"
+	"errors"
 
+	log "github.com/Sirupsen/logrus"
 	"github.com/docker/swarm/cluster"
-	"github.com/docker/swarm/scheduler/filter"
-	"github.com/docker/swarm/scheduler/strategy"
+	"github.com/docker/swarm/filter"
+	"github.com/docker/swarm/scheduler/builtin"
+	"github.com/docker/swarm/strategy"
 	"github.com/samalba/dockerclient"
 )
 
-type Scheduler struct {
-	sync.Mutex
-
-	cluster  *cluster.Cluster
-	strategy strategy.PlacementStrategy
-	filters  []filter.Filter
+type Scheduler interface {
+	Initialize(cluster *cluster.Cluster, strategy strategy.PlacementStrategy, filters []filter.Filter)
+	CreateContainer(config *dockerclient.ContainerConfig, name string) (*cluster.Container, error)
+	RemoveContainer(container *cluster.Container, force bool) error
 }
 
-func NewScheduler(cluster *cluster.Cluster, strategy strategy.PlacementStrategy, filters []filter.Filter) *Scheduler {
-	return &Scheduler{
-		cluster:  cluster,
-		strategy: strategy,
-		filters:  filters,
+var (
+	schedulers      map[string]Scheduler
+	ErrNotSupported = errors.New("scheduler not supported")
+)
+
+func init() {
+	schedulers = map[string]Scheduler{
+		"builtin": &builtin.BuiltinScheduler{},
 	}
 }
 
-// Find a nice home for our container.
-func (s *Scheduler) selectNodeForContainer(config *dockerclient.ContainerConfig) (*cluster.Node, error) {
-	candidates := s.cluster.Nodes()
-
-	accepted, err := filter.ApplyFilters(s.filters, config, candidates)
-	if err != nil {
-		return nil, err
+func New(name string, cluster *cluster.Cluster, strategy strategy.PlacementStrategy, filters []filter.Filter) (Scheduler, error) {
+	if scheduler, exists := schedulers[name]; exists {
+		log.WithField("name", name).Debug("Initializing scheduler")
+		scheduler.Initialize(cluster, strategy, filters)
+		return scheduler, nil
 	}
-
-	return s.strategy.PlaceContainer(config, accepted)
-}
-
-// Schedule a brand new container into the cluster.
-func (s *Scheduler) CreateContainer(config *dockerclient.ContainerConfig, name string) (*cluster.Container, error) {
-	/*Disable for now
-	if config.Memory == 0 || config.CpuShares == 0 {
-		return nil, fmt.Errorf("Creating containers in clustering mode requires resource constraints (-c and -m) to be set")
-	}
-	*/
-
-	s.Lock()
-	defer s.Unlock()
-
-	node, err := s.selectNodeForContainer(config)
-	if err != nil {
-		return nil, err
-	}
-	return s.cluster.DeployContainer(node, config, name)
-}
-
-// Remove a container from the cluster. Containers should always be destroyed
-// through the scheduler to guarantee atomicity.
-func (s *Scheduler) RemoveContainer(container *cluster.Container, force bool) error {
-	s.Lock()
-	defer s.Unlock()
-
-	return s.cluster.DestroyContainer(container, force)
+	return nil, ErrNotSupported
 }