[#15] Added healthy node rebalance

Signed-off-by: Denis Kirillov <denis@nspcc.ru>

pkg/pool/pool.go

@@ -45,15 +45,8 @@ func (pb *Builder) Build(ctx context.Context, options *BuilderOptions) (Pool, er
 	if len(pb.addresses) == 0 {
 		return nil, errors.New("no NeoFS peers configured")
 	}
-	totalWeight := 0.0
-	for _, w := range pb.weights {
-		totalWeight += w
-	}
-	for i, w := range pb.weights {
-		pb.weights[i] = w / totalWeight
-	}
 
-	options.weights = pb.weights
+	options.weights = adjustWeights(pb.weights)
 	options.addresses = pb.addresses
 	return newPool(ctx, options)
 }
@@ -108,26 +101,73 @@ func newPool(ctx context.Context, options *BuilderOptions) (Pool, error) {
 	ownerID := owner.NewIDFromNeo3Wallet(wallet)
 
 	pool := &pool{sampler: sampler, owner: ownerID, clientPacks: clientPacks}
-	go func() {
+	go startRebalance(ctx, pool, options)
+	return pool, nil
+}
+
+func startRebalance(ctx context.Context, p *pool, options *BuilderOptions) {
 	ticker := time.NewTimer(options.ClientRebalanceInterval)
+	buffer := make([]float64, len(options.weights))
+
 	for range ticker.C {
-			ok := true
-			for i, clientPack := range pool.clientPacks {
-				func() {
-					tctx, c := context.WithTimeout(ctx, options.NodeRequestTimeout)
-					defer c()
-					if _, err := clientPack.client.EndpointInfo(tctx); err != nil {
-						ok = false
-					}
-					pool.lock.Lock()
-					pool.clientPacks[i].healthy = ok
-					pool.lock.Unlock()
-				}()
-			}
+		updateNodesHealth(ctx, p, options, buffer)
 		ticker.Reset(options.ClientRebalanceInterval)
 	}
-	}()
-	return pool, nil
+}
+
+func updateNodesHealth(ctx context.Context, p *pool, options *BuilderOptions, bufferWeights []float64) {
+	if len(bufferWeights) != len(p.clientPacks) {
+		bufferWeights = make([]float64, len(p.clientPacks))
+	}
+	healthyChanged := false
+	wg := sync.WaitGroup{}
+	for i, cPack := range p.clientPacks {
+		wg.Add(1)
+		go func(i int, netmap client.Netmap) {
+			defer wg.Done()
+			ok := true
+			tctx, c := context.WithTimeout(ctx, options.NodeRequestTimeout)
+			defer c()
+			if _, err := netmap.EndpointInfo(tctx); err != nil {
+				ok = false
+				bufferWeights[i] = 0
+			}
+			if ok {
+				bufferWeights[i] = options.weights[i]
+			}
+
+			p.lock.Lock()
+			if p.clientPacks[i].healthy != ok {
+				p.clientPacks[i].healthy = ok
+				healthyChanged = true
+			}
+			p.lock.Unlock()
+		}(i, cPack.client)
+	}
+	wg.Wait()
+
+	if healthyChanged {
+		probabilities := adjustWeights(bufferWeights)
+		source := rand.NewSource(time.Now().UnixNano())
+		p.lock.Lock()
+		p.sampler = NewSampler(probabilities, source)
+		p.lock.Unlock()
+	}
+}
+
+func adjustWeights(weights []float64) []float64 {
+	adjusted := make([]float64, len(weights))
+	sum := 0.0
+	for _, weight := range weights {
+		sum += weight
+	}
+	if sum > 0 {
+		for i, weight := range weights {
+			adjusted[i] = weight / sum
+		}
+	}
+
+	return adjusted
 }
 
 func (p *pool) Connection() (client.Client, *session.Token, error) {

pkg/pool/sampler_test.go

@@ -1,9 +1,12 @@
 package pool
 
 import (
+	"context"
+	"fmt"
 	"math/rand"
 	"testing"
 
+	"github.com/nspcc-dev/neofs-api-go/pkg/client"
 	"github.com/stretchr/testify/require"
 )
 
@@ -38,3 +41,85 @@ func TestSamplerStability(t *testing.T) {
 		require.Equal(t, tc.expected, res, "probabilities: %v", tc.probabilities)
 	}
 }
+
+type netmapMock struct {
+	client.Client
+	name string
+	err  error
+}
+
+func newNetmapMock(name string, needErr bool) netmapMock {
+	var err error
+	if needErr {
+		err = fmt.Errorf("not available")
+	}
+	return netmapMock{name: name, err: err}
+}
+
+func (n netmapMock) EndpointInfo(_ context.Context, _ ...client.CallOption) (*client.EndpointInfo, error) {
+	return nil, n.err
+}
+
+func TestHealthyReweight(t *testing.T) {
+	var (
+		weights = []float64{0.9, 0.1}
+		names   = []string{"node0", "node1"}
+		options = &BuilderOptions{weights: weights}
+		buffer  = make([]float64, len(weights))
+	)
+
+	p := &pool{
+		sampler: NewSampler(weights, rand.NewSource(0)),
+		clientPacks: []*clientPack{
+			{client: newNetmapMock(names[0], true), healthy: true},
+			{client: newNetmapMock(names[1], false), healthy: true}},
+	}
+
+	// check getting first node connection before rebalance happened
+	connection0, _, err := p.Connection()
+	require.NoError(t, err)
+	mock0 := connection0.(netmapMock)
+	require.Equal(t, names[0], mock0.name)
+
+	updateNodesHealth(context.TODO(), p, options, buffer)
+
+	connection1, _, err := p.Connection()
+	require.NoError(t, err)
+	mock1 := connection1.(netmapMock)
+	require.Equal(t, names[1], mock1.name)
+
+	// enabled first node again
+	p.lock.Lock()
+	p.clientPacks[0].client = newNetmapMock(names[0], false)
+	p.lock.Unlock()
+
+	updateNodesHealth(context.TODO(), p, options, buffer)
+
+	connection0, _, err = p.Connection()
+	require.NoError(t, err)
+	mock0 = connection0.(netmapMock)
+	require.Equal(t, names[0], mock0.name)
+}
+
+func TestHealthyNoReweight(t *testing.T) {
+	var (
+		weights = []float64{0.9, 0.1}
+		names   = []string{"node0", "node1"}
+		options = &BuilderOptions{weights: weights}
+		buffer  = make([]float64, len(weights))
+	)
+
+	sampler := NewSampler(weights, rand.NewSource(0))
+	p := &pool{
+		sampler: sampler,
+		clientPacks: []*clientPack{
+			{client: newNetmapMock(names[0], false), healthy: true},
+			{client: newNetmapMock(names[1], false), healthy: true}},
+	}
+
+	updateNodesHealth(context.TODO(), p, options, buffer)
+
+	p.lock.RLock()
+	defer p.lock.RUnlock()
+	require.Truef(t, sampler == p.sampler, "Sampler must not be changed. Expected: %p, actual: %p", sampler, p.sampler)
+}