memory cache
Karolis Rusenas
parent
931f1695a9
commit
c0d2188932
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@ -0,0 +1,208 @@
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package memory
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import (
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"context"
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"fmt"
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"strings"
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"time"
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)
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type requestType int
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// Request types
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const (
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GET requestType = iota
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SET
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DELETE
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EXPIRE
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COPY
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)
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type (
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// Value - value is stored together with access and creation time
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Value struct {
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ctime time.Time
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atime time.Time
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value []byte
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}
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// Cache - cache container with a map of values and defaults
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Cache struct {
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cache map[string]*Value
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ctimeExpiry time.Duration // creation time
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atimeExpiry time.Duration // access time
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expiryTick time.Duration
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requestChannel chan *request
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}
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request struct {
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requestType
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key string
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value []byte
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responseChannel chan *response
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}
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response struct {
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error
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existingValue []byte
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mapCopy map[string][]byte
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value []byte
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}
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)
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func (c *Cache) isOld(v *Value) bool {
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if (c.ctimeExpiry != time.Duration(0)) && (time.Now().Sub(v.ctime) > c.ctimeExpiry) {
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return true
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}
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if (c.atimeExpiry != time.Duration(0)) && (time.Now().Sub(v.atime) > c.atimeExpiry) {
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return true
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}
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return false
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}
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// NewMemoryCache - creates new cache
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func NewMemoryCache(ctimeExpiry, atimeExpiry, expiryTick time.Duration) *Cache {
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c := &Cache{
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cache: make(map[string]*Value),
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ctimeExpiry: ctimeExpiry,
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atimeExpiry: atimeExpiry,
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expiryTick: expiryTick,
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requestChannel: make(chan *request),
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}
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go c.service()
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if ctimeExpiry != time.Duration(0) || atimeExpiry != time.Duration(0) {
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go c.expiryService()
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}
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return c
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}
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func (c *Cache) service() {
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for {
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req := <-c.requestChannel
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resp := &response{}
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switch req.requestType {
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case GET:
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val, ok := c.cache[req.key]
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if !ok {
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resp.error = fmt.Errorf("key '%v' not found", req.key)
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} else if c.isOld(val) {
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resp.error = fmt.Errorf("key '%v' expired (atime %v)", req.key, val.atime)
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delete(c.cache, req.key)
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} else {
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// update atime
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val.atime = time.Now()
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c.cache[req.key] = val
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resp.value = val.value
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}
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req.responseChannel <- resp
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case SET:
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c.cache[req.key] = &Value{
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value: req.value,
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ctime: time.Now(),
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atime: time.Now(),
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}
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req.responseChannel <- resp
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case DELETE:
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delete(c.cache, req.key)
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req.responseChannel <- resp
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case EXPIRE:
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for k, v := range c.cache {
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if c.isOld(v) {
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delete(c.cache, k)
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}
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}
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// no response
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case COPY:
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resp.mapCopy = make(map[string][]byte)
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for k, v := range c.cache {
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resp.mapCopy[k] = v.value
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}
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req.responseChannel <- resp
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default:
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resp.error = fmt.Errorf("invalid request type: %v", req.requestType)
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req.responseChannel <- resp
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}
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}
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}
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// Get - looks up value and returns it
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func (c *Cache) Get(ctx context.Context, key string) ([]byte, error) {
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respChannel := make(chan *response)
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c.requestChannel <- &request{
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requestType: GET,
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key: key,
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responseChannel: respChannel,
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}
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resp := <-respChannel
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return resp.value, resp.error
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}
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// Put - sets key/string. Overwrites existing key
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func (c *Cache) Put(ctx context.Context, key string, value []byte) error {
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respChannel := make(chan *response)
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c.requestChannel <- &request{
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requestType: SET,
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key: key,
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value: value,
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responseChannel: respChannel,
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}
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resp := <-respChannel
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return resp.error
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}
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// Del - deletes key
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func (c *Cache) Delete(ctx context.Context, key string) error {
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respChannel := make(chan *response)
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c.requestChannel <- &request{
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requestType: DELETE,
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key: key,
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responseChannel: respChannel,
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}
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resp := <-respChannel
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return resp.error
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}
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// List all values for specified prefix
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func (c *Cache) List(prefix string) ([][]byte, error) {
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respChannel := make(chan *response)
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c.requestChannel <- &request{
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requestType: COPY,
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responseChannel: respChannel,
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}
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resp := <-respChannel
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var list [][]byte
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for k, v := range resp.mapCopy {
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if strings.HasPrefix(k, prefix) {
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list = append(list, v)
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}
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}
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return list, nil
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}
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// Copy - makes a copy of inmemory map
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func (c *Cache) Copy() map[string][]byte {
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respChannel := make(chan *response)
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c.requestChannel <- &request{
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requestType: COPY,
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responseChannel: respChannel,
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}
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resp := <-respChannel
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return resp.mapCopy
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}
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func (c *Cache) expiryService() {
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ticker := time.NewTicker(c.expiryTick)
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defer ticker.Stop()
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for {
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select {
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case <-ticker.C:
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c.requestChannel <- &request{
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requestType: EXPIRE,
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}
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}
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}
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}
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@ -0,0 +1,84 @@
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package memory
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import (
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"context"
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"log"
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"testing"
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"time"
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)
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func TestCacheSetGet(t *testing.T) {
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c := NewMemoryCache(100*time.Millisecond, 100*time.Millisecond, 10*time.Millisecond)
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err := c.Put(context.Background(), "a", []byte("b"))
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if err != nil {
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t.Errorf("failed to SET a key, got error: %s", err)
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}
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val, err := c.Get(context.Background(), "a")
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if err != nil {
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t.Errorf("failed to GET a key, got error: %s", err)
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}
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if string(val) != "b" {
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log.Panicf("value %v", val)
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}
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cc := c.Copy()
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if len(cc) != 1 {
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t.Errorf("expected 1 item, got: %d", len(cc))
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}
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}
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func TestCacheDel(t *testing.T) {
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c := NewMemoryCache(100*time.Millisecond, 100*time.Millisecond, 10*time.Millisecond)
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err := c.Put(context.Background(), "a", []byte("b"))
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if err != nil {
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t.Errorf("failed to SET a key, got error: %s", err)
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}
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val, err := c.Get(context.Background(), "a")
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if err != nil {
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t.Errorf("failed to GET a key, got error: %s", err)
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}
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if string(val) != "b" {
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log.Panicf("value %v", val)
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}
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err = c.Delete(context.Background(), "a")
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if err != nil {
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t.Errorf("faield to delete entry, got error: %s", err)
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}
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_, err = c.Get(context.Background(), "a")
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if err == nil {
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t.Errorf("expected to get an error after deletion, but got nil")
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}
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}
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func TestCacheExpiration(t *testing.T) {
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c := NewMemoryCache(100*time.Millisecond, 100*time.Millisecond, 10*time.Millisecond)
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err := c.Put(context.Background(), "a", []byte("b"))
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if err != nil {
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t.Errorf("failed to SET a key, got error: %s", err)
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}
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val, err := c.Get(context.Background(), "a")
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if err != nil {
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t.Errorf("failed to GET a key, got error: %s", err)
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}
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if string(val) != "b" {
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log.Panicf("value %v", val)
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}
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time.Sleep(200 * time.Millisecond)
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_, err = c.Get(context.Background(), "a")
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if err == nil {
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t.Errorf("expected to get an error after deletion, but got nil")
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}
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}
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