[m3cluster] Expose placement algorithm in placement service (#2858)

src/cluster/placement/service/mirrored_custom_groups_test.go

@@ -59,7 +59,6 @@ const (
 	instG3I1 = "g3_i1"
 	instG3I2 = "g3_i2"
 	instG3I3 = "g3_i3"
-
 )
 
 var (
@@ -205,7 +204,7 @@ func mirroredCustomGroupSelectorSetup(t *testing.T) *mirroredCustomGroupSelector
 	tctx.Groups = testGroups
 
 	opts := placement.NewOptions().
-		SetValidZone(zone). 
+		SetValidZone(zone).
 		SetIsMirrored(true)
 
 	tctx.Selector = selector.NewMirroredCustomGroupSelector(
@@ -217,7 +216,7 @@ func mirroredCustomGroupSelectorSetup(t *testing.T) *mirroredCustomGroupSelector
 
 	tctx.KVStore = mem.NewStore()
 	tctx.Storage = placementstorage.NewPlacementStorage(tctx.KVStore, "placement", tctx.Opts)
-	tctx.Service = NewPlacementService(tctx.Storage, tctx.Opts)
+	tctx.Service = NewPlacementService(tctx.Storage, WithPlacementOptions(tctx.Opts))
 	return tctx
 }
 

src/cluster/placement/service/operator.go

@@ -31,10 +31,10 @@ import (
 // given placement.
 // If initialPlacement is nil, BuildInitialPlacement must be called before any operations on the
 // placement.
-func NewPlacementOperator(initialPlacement placement.Placement, opts placement.Options) placement.Operator {
+func NewPlacementOperator(initialPlacement placement.Placement, opts ...Option) placement.Operator {
 	store := newDummyStore(initialPlacement)
 	return &placementOperator{
-		placementServiceImpl: newPlacementServiceImpl(opts, store),
+		placementServiceImpl: newPlacementServiceImpl(store, opts...),
 		store:                store,
 	}
 }
@@ -97,4 +97,3 @@ func (d *dummyStore) Placement() (placement.Placement, error) {
 	}
 	return d.curPlacement, nil
 }
-

src/cluster/placement/service/operator_test.go

@@ -25,21 +25,20 @@ import (
 	"testing"
 
 	"github.com/m3db/m3/src/cluster/placement"
-
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
 func TestOperator(t *testing.T) {
 	type testDeps struct {
 		options placement.Options
-		op placement.Operator
+		op      placement.Operator
 	}
 	setup := func(t *testing.T) testDeps {
 		options := placement.NewOptions().SetAllowAllZones(true)
 		return testDeps{
 			options: options,
-			op: NewPlacementOperator(nil, options),
+			op:      NewPlacementOperator(nil, WithPlacementOptions(options)),
 		}
 	}
 
@@ -60,7 +59,7 @@ func TestOperator(t *testing.T) {
 
 	t.Run("end-to-end flow", func(t *testing.T) {
 		tdeps := setup(t)
-		op := NewPlacementOperator(nil, tdeps.options)
+		op := NewPlacementOperator(nil, WithPlacementOptions(tdeps.options))
 		store := newMockStorage()
 
 		pl, err := op.BuildInitialPlacement([]placement.Instance{newTestInstance()}, 10, 1)
@@ -81,7 +80,7 @@ func TestOperator(t *testing.T) {
 		require.NoError(t, err)
 
 		// expect exactly one version increment, from store.SetIfNotExist
-		assert.Equal(t, initialVersion + 1, pl.Version())
+		assert.Equal(t, initialVersion+1, pl.Version())
 
 		// spot check the results
 		allAvailable := true
@@ -94,15 +93,15 @@ func TestOperator(t *testing.T) {
 	})
 }
 
-type dummyStoreTestDeps struct{
+type dummyStoreTestDeps struct {
 	store *dummyStore
-	pl placement.Placement
+	pl    placement.Placement
 }
 
 func dummyStoreSetup(t *testing.T) dummyStoreTestDeps {
 	return dummyStoreTestDeps{
 		store: newDummyStore(nil),
-		pl: placement.NewPlacement(),
+		pl:    placement.NewPlacement(),
 	}
 }
 

src/cluster/placement/service/service.go

@@ -27,7 +27,6 @@ import (
 	"github.com/m3db/m3/src/cluster/placement/algo"
 	"github.com/m3db/m3/src/cluster/placement/selector"
 	"github.com/m3db/m3/src/cluster/shard"
-
 	"go.uber.org/zap"
 )
 
@@ -37,36 +36,79 @@ type placementService struct {
 }
 
 // NewPlacementService returns an instance of placement service.
-func NewPlacementService(s placement.Storage, opts placement.Options) placement.Service {
+func NewPlacementService(s placement.Storage, opts ...Option) placement.Service {
 	return &placementService{
 		Storage: s,
 		placementServiceImpl: newPlacementServiceImpl(
-			opts,
 			s,
-
+			opts...,
 		),
 	}
 }
 
+type options struct {
+	placementAlgorithm placement.Algorithm
+	placementOpts      placement.Options
+}
+
+// Option is an interface for PlacementService options.
+type Option interface {
+	apply(*options)
+}
+
+// WithAlgorithm sets the algorithm implementation that will be used by PlacementService.
+func WithAlgorithm(algo placement.Algorithm) Option {
+	return &algorithmOption{placementAlgorithm: algo}
+}
+
+type algorithmOption struct {
+	placementAlgorithm placement.Algorithm
+}
+
+func (a *algorithmOption) apply(opts *options) {
+	opts.placementAlgorithm = a.placementAlgorithm
+}
+
+type placementOptionsOption struct {
+	opts placement.Options
+}
+
+func (a *placementOptionsOption) apply(opts *options) {
+	opts.placementOpts = a.opts
+}
+
+// WithPlacementOptions sets the placement options for PlacementService.
+func WithPlacementOptions(opts placement.Options) Option {
+	return &placementOptionsOption{opts: opts}
+}
+
 func newPlacementServiceImpl(
-	opts placement.Options,
 	storage minimalPlacementStorage,
+	opts ...Option,
 ) *placementServiceImpl {
-	if opts == nil {
-		opts = placement.NewOptions()
+	o := options{
+		placementOpts: placement.NewOptions(),
+	}
+
+	for _, opt := range opts {
+		opt.apply(&o)
+	}
+
+	if o.placementAlgorithm == nil {
+		o.placementAlgorithm = algo.NewAlgorithm(o.placementOpts)
 	}
 
-	instanceSelector := opts.InstanceSelector()
+	instanceSelector := o.placementOpts.InstanceSelector()
 	if instanceSelector == nil {
-		instanceSelector = selector.NewInstanceSelector(opts)
+		instanceSelector = selector.NewInstanceSelector(o.placementOpts)
 	}
 
 	return &placementServiceImpl{
 		store:    storage,
-		opts:     opts,
-		algo:     algo.NewAlgorithm(opts),
+		opts:     o.placementOpts,
+		algo:     o.placementAlgorithm,
 		selector: instanceSelector,
-		logger:   opts.InstrumentOptions().Logger(),
+		logger:   o.placementOpts.InstrumentOptions().Logger(),
 	}
 }