consistenthash_test.go

Documentation: github.com/golang/groupcache/consistenthash

     1  /*
     2  Copyright 2013 Google Inc.
     3  
     4  Licensed under the Apache License, Version 2.0 (the "License");
     5  you may not use this file except in compliance with the License.
     6  You may obtain a copy of the License at
     7  
     8       http://www.apache.org/licenses/LICENSE-2.0
     9  
    10  Unless required by applicable law or agreed to in writing, software
    11  distributed under the License is distributed on an "AS IS" BASIS,
    12  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  See the License for the specific language governing permissions and
    14  limitations under the License.
    15  */
    16  
    17  package consistenthash
    18  
    19  import (
    20  	"fmt"
    21  	"strconv"
    22  	"testing"
    23  )
    24  
    25  func TestHashing(t *testing.T) {
    26  
    27  	// Override the hash function to return easier to reason about values. Assumes
    28  	// the keys can be converted to an integer.
    29  	hash := New(3, func(key []byte) uint32 {
    30  		i, err := strconv.Atoi(string(key))
    31  		if err != nil {
    32  			panic(err)
    33  		}
    34  		return uint32(i)
    35  	})
    36  
    37  	// Given the above hash function, this will give replicas with "hashes":
    38  	// 2, 4, 6, 12, 14, 16, 22, 24, 26
    39  	hash.Add("6", "4", "2")
    40  
    41  	testCases := map[string]string{
    42  		"2":  "2",
    43  		"11": "2",
    44  		"23": "4",
    45  		"27": "2",
    46  	}
    47  
    48  	for k, v := range testCases {
    49  		if hash.Get(k) != v {
    50  			t.Errorf("Asking for %s, should have yielded %s", k, v)
    51  		}
    52  	}
    53  
    54  	// Adds 8, 18, 28
    55  	hash.Add("8")
    56  
    57  	// 27 should now map to 8.
    58  	testCases["27"] = "8"
    59  
    60  	for k, v := range testCases {
    61  		if hash.Get(k) != v {
    62  			t.Errorf("Asking for %s, should have yielded %s", k, v)
    63  		}
    64  	}
    65  
    66  }
    67  
    68  func TestConsistency(t *testing.T) {
    69  	hash1 := New(1, nil)
    70  	hash2 := New(1, nil)
    71  
    72  	hash1.Add("Bill", "Bob", "Bonny")
    73  	hash2.Add("Bob", "Bonny", "Bill")
    74  
    75  	if hash1.Get("Ben") != hash2.Get("Ben") {
    76  		t.Errorf("Fetching 'Ben' from both hashes should be the same")
    77  	}
    78  
    79  	hash2.Add("Becky", "Ben", "Bobby")
    80  
    81  	if hash1.Get("Ben") != hash2.Get("Ben") ||
    82  		hash1.Get("Bob") != hash2.Get("Bob") ||
    83  		hash1.Get("Bonny") != hash2.Get("Bonny") {
    84  		t.Errorf("Direct matches should always return the same entry")
    85  	}
    86  
    87  }
    88  
    89  func BenchmarkGet8(b *testing.B)   { benchmarkGet(b, 8) }
    90  func BenchmarkGet32(b *testing.B)  { benchmarkGet(b, 32) }
    91  func BenchmarkGet128(b *testing.B) { benchmarkGet(b, 128) }
    92  func BenchmarkGet512(b *testing.B) { benchmarkGet(b, 512) }
    93  
    94  func benchmarkGet(b *testing.B, shards int) {
    95  
    96  	hash := New(50, nil)
    97  
    98  	var buckets []string
    99  	for i := 0; i < shards; i++ {
   100  		buckets = append(buckets, fmt.Sprintf("shard-%d", i))
   101  	}
   102  
   103  	hash.Add(buckets...)
   104  
   105  	b.ResetTimer()
   106  
   107  	for i := 0; i < b.N; i++ {
   108  		hash.Get(buckets[i&(shards-1)])
   109  	}
   110  }
   111
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