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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,111 @@ | ||
| package error_page | ||
|
|
||
| import ( | ||
| "bytes" | ||
| "crypto/md5" //nolint:gosec | ||
| "encoding/gob" | ||
| "sync" | ||
| "time" | ||
|
|
||
| "gh.tarampamp.am/error-pages/internal/template" | ||
| ) | ||
|
|
||
| type ( | ||
| // RenderedCache is a cache for rendered error pages. It's safe for concurrent use. | ||
| // It uses a hash of the template and props as a key. | ||
| // | ||
| // To remove expired items, call ClearExpired method periodically (a bit more often than the ttl). | ||
| RenderedCache struct { | ||
| ttl time.Duration | ||
|
|
||
| mu sync.RWMutex | ||
| items map[[32]byte]cacheItem // map[template_hash[0:15];props_hash[16:32]]cache_item | ||
| } | ||
|
|
||
| cacheItem struct { | ||
| content []byte | ||
| addedAtNano int64 | ||
| } | ||
| ) | ||
|
|
||
| // NewRenderedCache creates a new RenderedCache with the specified ttl. | ||
| func NewRenderedCache(ttl time.Duration) *RenderedCache { | ||
| return &RenderedCache{ttl: ttl, items: make(map[[32]byte]cacheItem)} | ||
| } | ||
|
|
||
| // genKey generates a key for the cache item by hashing the template and props. | ||
| func (rc *RenderedCache) genKey(template string, props template.Props) [32]byte { | ||
| var ( | ||
| key [32]byte | ||
| th, ph = hash(template), hash(props) // template hash, props hash | ||
| ) | ||
|
|
||
| copy(key[:16], th[:]) // first 16 bytes for the template hash | ||
| copy(key[16:], ph[:]) // last 16 bytes for the props hash | ||
|
|
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| return key | ||
| } | ||
|
|
||
| // Has checks if the cache has an item with the specified template and props. | ||
| func (rc *RenderedCache) Has(template string, props template.Props) bool { | ||
| var key = rc.genKey(template, props) | ||
|
|
||
| rc.mu.RLock() | ||
| _, ok := rc.items[key] | ||
| rc.mu.RUnlock() | ||
|
|
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| return ok | ||
| } | ||
|
|
||
| // Put adds a new item to the cache with the specified template, props, and content. | ||
| func (rc *RenderedCache) Put(template string, props template.Props, content []byte) { | ||
| var key = rc.genKey(template, props) | ||
|
|
||
| rc.mu.Lock() | ||
| rc.items[key] = cacheItem{content: content, addedAtNano: time.Now().UnixNano()} | ||
| rc.mu.Unlock() | ||
| } | ||
|
|
||
| // Get returns the content of the item with the specified template and props. | ||
| func (rc *RenderedCache) Get(template string, props template.Props) ([]byte, bool) { | ||
| var key = rc.genKey(template, props) | ||
|
|
||
| rc.mu.RLock() | ||
| item, ok := rc.items[key] | ||
| rc.mu.RUnlock() | ||
|
|
||
| return item.content, ok | ||
| } | ||
|
|
||
| // ClearExpired removes all expired items from the cache. | ||
| func (rc *RenderedCache) ClearExpired() { | ||
| rc.mu.Lock() | ||
|
|
||
| var now = time.Now().UnixNano() | ||
|
|
||
| for key, item := range rc.items { | ||
| if now-item.addedAtNano > rc.ttl.Nanoseconds() { | ||
| delete(rc.items, key) | ||
| } | ||
| } | ||
|
|
||
| rc.mu.Unlock() | ||
| } | ||
|
|
||
| // Clear removes all items from the cache. | ||
| func (rc *RenderedCache) Clear() { | ||
| rc.mu.Lock() | ||
| clear(rc.items) | ||
| rc.mu.Unlock() | ||
| } | ||
|
|
||
| // hash returns an MD5 hash of the provided value (it may be any built-in type). | ||
| func hash(in any) [16]byte { | ||
| var b bytes.Buffer | ||
|
|
||
| if err := gob.NewEncoder(&b).Encode(in); err != nil { | ||
| return [16]byte{} // never happens because we encode only built-in types | ||
| } | ||
|
|
||
| return md5.Sum(b.Bytes()) //nolint:gosec | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,86 @@ | ||
| package error_page_test | ||
|
|
||
| import ( | ||
| "strconv" | ||
| "sync" | ||
| "testing" | ||
| "time" | ||
|
|
||
| "github.com/stretchr/testify/assert" | ||
|
|
||
| "gh.tarampamp.am/error-pages/internal/http/handlers/error_page" | ||
| "gh.tarampamp.am/error-pages/internal/template" | ||
| ) | ||
|
|
||
| func TestRenderedCache_CRUD(t *testing.T) { | ||
| t.Parallel() | ||
|
|
||
| var cache = error_page.NewRenderedCache(time.Millisecond) | ||
|
|
||
| t.Run("has", func(t *testing.T) { | ||
| assert.False(t, cache.Has("template", template.Props{})) | ||
| cache.Put("template", template.Props{}, []byte("content")) | ||
| assert.True(t, cache.Has("template", template.Props{})) | ||
|
|
||
| assert.False(t, cache.Has("template", template.Props{Code: 1})) | ||
| assert.False(t, cache.Has("foo", template.Props{Code: 1})) | ||
| }) | ||
|
|
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| t.Run("exists", func(t *testing.T) { | ||
| var got, ok = cache.Get("template", template.Props{}) | ||
|
|
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| assert.True(t, ok) | ||
| assert.Equal(t, []byte("content"), got) | ||
|
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| cache.Clear() | ||
|
|
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| assert.False(t, cache.Has("template", template.Props{})) | ||
| }) | ||
|
|
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| t.Run("not exists", func(t *testing.T) { | ||
| var got, ok = cache.Get("template", template.Props{Code: 2}) | ||
|
|
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| assert.False(t, ok) | ||
| assert.Nil(t, got) | ||
| }) | ||
|
|
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| t.Run("race condition provocation", func(t *testing.T) { | ||
| var wg sync.WaitGroup | ||
|
|
||
| for i := 0; i < 100; i++ { | ||
| wg.Add(2) | ||
|
|
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| go func(i int) { | ||
| defer wg.Done() | ||
|
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| cache.Get("template", template.Props{}) | ||
| cache.Put("template"+strconv.Itoa(i), template.Props{}, []byte("content")) | ||
| cache.Has("template", template.Props{}) | ||
| }(i) | ||
|
|
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| go func() { | ||
| defer wg.Done() | ||
|
|
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| cache.ClearExpired() | ||
| }() | ||
| } | ||
|
|
||
| wg.Wait() | ||
| }) | ||
| } | ||
|
|
||
| func TestRenderedCache_Expiring(t *testing.T) { | ||
| t.Parallel() | ||
|
|
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| var cache = error_page.NewRenderedCache(10 * time.Millisecond) | ||
|
|
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| cache.Put("template", template.Props{}, []byte("content")) | ||
| cache.ClearExpired() | ||
| assert.True(t, cache.Has("template", template.Props{})) | ||
|
|
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| <-time.After(10 * time.Millisecond) | ||
|
|
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| assert.True(t, cache.Has("template", template.Props{})) // expired, but not cleared yet | ||
| cache.ClearExpired() | ||
| assert.False(t, cache.Has("template", template.Props{})) // cleared | ||
| } |
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