2 files changed, 191 insertions, 0 deletions
diff --git a/vendor/github.com/golang/groupcache/consistenthash/consistenthash.go b/vendor/github.com/golang/groupcache/consistenthash/consistenthash.go
new file mode 100644
index 000000000..a9c56f076
--- /dev/null
+++ b/vendor/github.com/golang/groupcache/consistenthash/consistenthash.go
@@ -0,0 +1,81 @@
+/*
+Copyright 2013 Google Inc.
+
+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 consistenthash provides an implementation of a ring hash.
+package consistenthash
+
+import (
+	"hash/crc32"
+	"sort"
+	"strconv"
+)
+
+type Hash func(data []byte) uint32
+
+type Map struct {
+	hash     Hash
+	replicas int
+	keys     []int // Sorted
+	hashMap  map[int]string
+}
+
+func New(replicas int, fn Hash) *Map {
+	m := &Map{
+		replicas: replicas,
+		hash:     fn,
+		hashMap:  make(map[int]string),
+	}
+	if m.hash == nil {
+		m.hash = crc32.ChecksumIEEE
+	}
+	return m
+}
+
+// Returns true if there are no items available.
+func (m *Map) IsEmpty() bool {
+	return len(m.keys) == 0
+}
+
+// Adds some keys to the hash.
+func (m *Map) Add(keys ...string) {
+	for _, key := range keys {
+		for i := 0; i < m.replicas; i++ {
+			hash := int(m.hash([]byte(strconv.Itoa(i) + key)))
+			m.keys = append(m.keys, hash)
+			m.hashMap[hash] = key
+		}
+	}
+	sort.Ints(m.keys)
+}
+
+// Gets the closest item in the hash to the provided key.
+func (m *Map) Get(key string) string {
+	if m.IsEmpty() {
+		return ""
+	}
+
+	hash := int(m.hash([]byte(key)))
+
+	// Binary search for appropriate replica.
+	idx := sort.Search(len(m.keys), func(i int) bool { return m.keys[i] >= hash })
+
+	// Means we have cycled back to the first replica.
+	if idx == len(m.keys) {
+		idx = 0
+	}
+
+	return m.hashMap[m.keys[idx]]
+}
diff --git a/vendor/github.com/golang/groupcache/consistenthash/consistenthash_test.go b/vendor/github.com/golang/groupcache/consistenthash/consistenthash_test.go
new file mode 100644
index 000000000..1a37fd7ff
--- /dev/null
+++ b/vendor/github.com/golang/groupcache/consistenthash/consistenthash_test.go
@@ -0,0 +1,110 @@
+/*
+Copyright 2013 Google Inc.
+
+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 consistenthash
+
+import (
+	"fmt"
+	"strconv"
+	"testing"
+)
+
+func TestHashing(t *testing.T) {
+
+	// Override the hash function to return easier to reason about values. Assumes
+	// the keys can be converted to an integer.
+	hash := New(3, func(key []byte) uint32 {
+		i, err := strconv.Atoi(string(key))
+		if err != nil {
+			panic(err)
+		}
+		return uint32(i)
+	})
+
+	// Given the above hash function, this will give replicas with "hashes":
+	// 2, 4, 6, 12, 14, 16, 22, 24, 26
+	hash.Add("6", "4", "2")
+
+	testCases := map[string]string{
+		"2":  "2",
+		"11": "2",
+		"23": "4",
+		"27": "2",
+	}
+
+	for k, v := range testCases {
+		if hash.Get(k) != v {
+			t.Errorf("Asking for %s, should have yielded %s", k, v)
+		}
+	}
+
+	// Adds 8, 18, 28
+	hash.Add("8")
+
+	// 27 should now map to 8.
+	testCases["27"] = "8"
+
+	for k, v := range testCases {
+		if hash.Get(k) != v {
+			t.Errorf("Asking for %s, should have yielded %s", k, v)
+		}
+	}
+
+}
+
+func TestConsistency(t *testing.T) {
+	hash1 := New(1, nil)
+	hash2 := New(1, nil)
+
+	hash1.Add("Bill", "Bob", "Bonny")
+	hash2.Add("Bob", "Bonny", "Bill")
+
+	if hash1.Get("Ben") != hash2.Get("Ben") {
+		t.Errorf("Fetching 'Ben' from both hashes should be the same")
+	}
+
+	hash2.Add("Becky", "Ben", "Bobby")
+
+	if hash1.Get("Ben") != hash2.Get("Ben") ||
+		hash1.Get("Bob") != hash2.Get("Bob") ||
+		hash1.Get("Bonny") != hash2.Get("Bonny") {
+		t.Errorf("Direct matches should always return the same entry")
+	}
+
+}
+
+func BenchmarkGet8(b *testing.B)   { benchmarkGet(b, 8) }
+func BenchmarkGet32(b *testing.B)  { benchmarkGet(b, 32) }
+func BenchmarkGet128(b *testing.B) { benchmarkGet(b, 128) }
+func BenchmarkGet512(b *testing.B) { benchmarkGet(b, 512) }
+
+func benchmarkGet(b *testing.B, shards int) {
+
+	hash := New(50, nil)
+
+	var buckets []string
+	for i := 0; i < shards; i++ {
+		buckets = append(buckets, fmt.Sprintf("shard-%d", i))
+	}
+
+	hash.Add(buckets...)
+
+	b.ResetTimer()
+
+	for i := 0; i < b.N; i++ {
+		hash.Get(buckets[i&(shards-1)])
+	}
+}