snapshot of https://github.com/grpc/grpc-go.git (master, 2026-09-15; blobs > 131072B omitted)

balancer/autosharding/slice_map_test.go

@@ -0,0 +1,216 @@
+/*
+ *
+ * Copyright 2026 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package autosharding
+
+import (
+	"bytes"
+	"fmt"
+	"slices"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+)
+
+func (s) TestSliceMap_Lookup(t *testing.T) {
+	sm := &sliceMap{
+		slices: []sliceMapEntry{
+			{startKey: []byte("a"), endpoints: []int{1}},
+			{startKey: []byte("d"), endpoints: []int{2}},
+			{startKey: []byte("f"), endpoints: []int{3}},
+		},
+	}
+
+	tests := []struct {
+		name string
+		key  []byte
+		want int
+	}{
+		{
+			name: "exact-match-first",
+			key:  []byte("a"),
+			want: 0,
+		},
+		{
+			name: "exact-match-middle",
+			key:  []byte("d"),
+			want: 1,
+		},
+		{
+			name: "exact-match-last",
+			key:  []byte("f"),
+			want: 2,
+		},
+		{
+			name: "between-first-and-middle",
+			key:  []byte("c"),
+			want: 0,
+		},
+		{
+			name: "between-middle-and-last",
+			key:  []byte("e"),
+			want: 1,
+		},
+		{
+			name: "after-last",
+			key:  []byte("g"),
+			want: 2,
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			if got := sm.lookup(tc.key); got != tc.want {
+				t.Errorf("lookup(%q) = %d, want %d", tc.key, got, tc.want)
+			}
+		})
+	}
+}
+
+func (s) TestSliceMap_Lookup_Empty(t *testing.T) {
+	sm := &sliceMap{}
+	if got := sm.lookup([]byte("a")); got != -1 {
+		t.Errorf("lookup() on empty map = %d, want -1", got)
+	}
+}
+
+func (s) TestBuildSliceMap(t *testing.T) {
+	// Setup endpointMap with unsorted order in map to verify deterministic
+	// sorting of fallbackPool.
+	epMap := &endpointMap{
+		m: map[string]*endpointState{
+			"hostC": {index: 2},
+			"hostA": {index: 0},
+			"hostB": {index: 1},
+		},
+	}
+
+	tests := []struct {
+		name       string
+		assignment *assignment
+		want       *sliceMap
+	}{
+		{
+			name:       "nil-assignment-startup",
+			assignment: nil,
+			want:       &sliceMap{fallbackPool: []int{0, 1, 2}},
+		},
+		{
+			name: "valid-assignment",
+			assignment: &assignment{
+				endpointNames: []string{"hostA", "hostB", "hostC"},
+				slices: []slice{
+					{startKey: []byte("a"), endpoints: []int{0, 1}}, // hostA, hostB -> indices 0, 1
+					{startKey: []byte("m"), endpoints: []int{1, 2}}, // hostB, hostC -> indices 1, 2
+				},
+				generation: 42,
+			},
+			want: &sliceMap{
+				slices: []sliceMapEntry{
+					{startKey: []byte("a"), endpoints: []int{0, 1}},
+					{startKey: []byte("m"), endpoints: []int{1, 2}},
+				},
+				fallbackPool: []int{0, 1, 2},
+				generation:   42,
+			},
+		},
+		{
+			name: "assignment-with-unknown-host",
+			assignment: &assignment{
+				endpointNames: []string{"hostA", "hostUnknown", "hostC"},
+				slices: []slice{
+					{startKey: []byte("a"), endpoints: []int{0, 1}}, // hostUnknown is skipped
+				},
+				generation: 43,
+			},
+			want: &sliceMap{
+				slices: []sliceMapEntry{
+					{startKey: []byte("a"), endpoints: []int{0}}, // Only hostA (index 0)
+				},
+				fallbackPool: []int{0, 1, 2},
+				generation:   43,
+			},
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			got := buildSliceMap(epMap, tc.assignment)
+			if diff := cmp.Diff(tc.want, got); diff != "" {
+				t.Errorf("buildSliceMap() diff (-want +got):\n%s", diff)
+			}
+		})
+	}
+}
+
+func (e sliceMapEntry) Equal(b sliceMapEntry) bool {
+	return bytes.Equal(e.startKey, b.startKey) && slices.Equal(e.endpoints, b.endpoints)
+}
+
+func (sm *sliceMap) Equal(b *sliceMap) bool {
+	if sm == nil || b == nil {
+		return sm == b
+	}
+	fallbackPoolEqual := slices.Equal(sm.fallbackPool, b.fallbackPool)
+	slicesEqual := slices.EqualFunc(sm.slices, b.slices, func(x, y sliceMapEntry) bool { return x.Equal(y) })
+	return sm.generation == b.generation && fallbackPoolEqual && slicesEqual
+}
+
+func BenchmarkSliceMap_Lookup(b *testing.B) {
+	for _, numSlices := range []int{1, 10, 100, 1000, 10000} {
+		for _, keySize := range []int{16, 32, 64, 128, 256, 512} {
+			b.Run(fmt.Sprintf("slices_%d_keySize_%d", numSlices, keySize), func(b *testing.B) {
+				sm := &sliceMap{
+					slices: make([]sliceMapEntry, numSlices),
+				}
+				for i := 0; i < numSlices; i++ {
+					// Generate lexicographically sorted keys to serve as slice
+					// boundaries.  We multiply by 1000 to create ranges (gaps) between
+					// successive slices (e.g., Slice 0 covers [0, 1000), Slice 1 covers
+					// [1000, 2000)). This allows us to test lookups that fall
+					// *mid-slice*, rather than just exact matches.
+					//
+					// We use zero-padding on the left via "%0*d" (where * is the keySize
+					// width).  This fills the key to its full length (e.g., 512 bytes)
+					// with leading zeros.  Scanning long identical prefixes forces
+					// bytes.Compare to traverse the full length, simulating a
+					// conservative, worst-case latency scenario.
+					key := fmt.Appendf(nil, "%0*d", keySize, i*1000)
+					sm.slices[i] = sliceMapEntry{startKey: key, endpoints: []int{i}}
+				}
+
+				// Pre-generate a pool of lookup keys. This helps avoid
+				// measuring string formatting overhead inside the timer loop.
+				lookupKeys := make([][]byte, 10000)
+				for i := 0; i < 10000; i++ {
+					// Distribute the 10,000 lookup keys proportionally across the entire
+					// synthetic keyspace [0, numSlices * 1000). This ensures a good mix
+					// of boundary hits and interior hits.
+					val := i * (numSlices * 1000) / 10000
+					lookupKeys[i] = fmt.Appendf(nil, "%0*d", keySize, val)
+				}
+
+				var i int
+				for b.Loop() {
+					sm.lookup(lookupKeys[i%10000])
+					i++
+				}
+			})
+		}
+	}
+}