031dfede90
* pkg/cache: fix race in Add() and Evict() This fixes a race in Add() when the shard is at max capacity and the key being added is already stored. Previously, the shard would evict a random value - when all it needed to do was replace an existing value. There was a race in how Evict() picked which key to remove, which would cause concurrent calls to Evict() to remove the same key. Additionally, this commit removes a lot of the lock contention and a race around Add() and Evict() by changing them to immediately hold the write lock. Previously, they would check conditions with the read lock held and not re-check those conditions once the write lock was acquired (this is a race). * pkg/cache: code review comments * pkg/cache: simplify Add() logic
139 lines
2.5 KiB
Go
139 lines
2.5 KiB
Go
package cache
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import (
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"sync"
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"testing"
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)
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func TestShardAddAndGet(t *testing.T) {
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s := newShard(1)
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s.Add(1, 1)
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if _, found := s.Get(1); !found {
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t.Fatal("Failed to find inserted record")
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}
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s.Add(2, 1)
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if _, found := s.Get(1); found {
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t.Fatal("Failed to evict record")
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}
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if _, found := s.Get(2); !found {
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t.Fatal("Failed to find inserted record")
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}
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}
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func TestAddEvict(t *testing.T) {
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const size = 1024
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s := newShard(size)
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for i := uint64(0); i < size; i++ {
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s.Add(i, 1)
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}
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for i := uint64(0); i < size; i++ {
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s.Add(i, 1)
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if s.Len() != size {
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t.Fatal("A item was unnecessarily evicted from the cache")
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}
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}
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}
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func TestShardLen(t *testing.T) {
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s := newShard(4)
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s.Add(1, 1)
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if l := s.Len(); l != 1 {
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t.Fatalf("Shard size should %d, got %d", 1, l)
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}
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s.Add(1, 1)
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if l := s.Len(); l != 1 {
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t.Fatalf("Shard size should %d, got %d", 1, l)
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}
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s.Add(2, 2)
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if l := s.Len(); l != 2 {
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t.Fatalf("Shard size should %d, got %d", 2, l)
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}
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}
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func TestShardEvict(t *testing.T) {
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s := newShard(1)
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s.Add(1, 1)
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s.Add(2, 2)
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// 1 should be gone
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if _, found := s.Get(1); found {
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t.Fatal("Found item that should have been evicted")
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}
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}
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func TestShardLenEvict(t *testing.T) {
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s := newShard(4)
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s.Add(1, 1)
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s.Add(2, 1)
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s.Add(3, 1)
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s.Add(4, 1)
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if l := s.Len(); l != 4 {
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t.Fatalf("Shard size should %d, got %d", 4, l)
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}
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// This should evict one element
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s.Add(5, 1)
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if l := s.Len(); l != 4 {
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t.Fatalf("Shard size should %d, got %d", 4, l)
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}
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// Make sure we don't accidentally evict an element when
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// we the key is already stored.
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for i := 0; i < 4; i++ {
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s.Add(5, 1)
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if l := s.Len(); l != 4 {
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t.Fatalf("Shard size should %d, got %d", 4, l)
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}
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}
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}
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func TestShardEvictParallel(t *testing.T) {
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s := newShard(shardSize)
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for i := uint64(0); i < shardSize; i++ {
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s.Add(i, struct{}{})
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}
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start := make(chan struct{})
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var wg sync.WaitGroup
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for i := 0; i < shardSize; i++ {
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wg.Add(1)
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go func() {
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<-start
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s.Evict()
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wg.Done()
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}()
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}
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close(start) // start evicting in parallel
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wg.Wait()
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if s.Len() != 0 {
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t.Fatalf("Failed to evict all keys in parallel: %d", s.Len())
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}
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}
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func BenchmarkShard(b *testing.B) {
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s := newShard(shardSize)
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b.ResetTimer()
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for i := 0; i < b.N; i++ {
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k := uint64(i) % shardSize * 2
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s.Add(k, 1)
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s.Get(k)
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}
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}
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func BenchmarkShardParallel(b *testing.B) {
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s := newShard(shardSize)
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b.ResetTimer()
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b.RunParallel(func(pb *testing.PB) {
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for i := uint64(0); pb.Next(); i++ {
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k := i % shardSize * 2
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s.Add(k, 1)
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s.Get(k)
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}
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})
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}
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