mirror of
https://github.com/minio/minio.git
synced 2025-11-08 21:24:55 -05:00
fix: remove persistence layer for metacache store in memory (#11538)
store the cache in-memory instead of disks to avoid large write amplifications for list heavy workloads, store in memory instead and let it auto expire.
This commit is contained in:
Harshavardhana
GitHub
270
pkg/objcache/objcache.go
Normal file
270
pkg/objcache/objcache.go
Normal file
@@ -0,0 +1,270 @@
|
||||
/*
|
||||
* Minio Cloud Storage, (C) 2021 Minio, 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 objcache implements in memory caching methods.
|
||||
package objcache
|
||||
|
||||
import (
|
||||
"bytes"
|
||||
"errors"
|
||||
"io"
|
||||
"sync"
|
||||
"time"
|
||||
|
||||
"github.com/valyala/bytebufferpool"
|
||||
)
|
||||
|
||||
const (
|
||||
// NoExpiry represents caches to be permanent and can only be deleted.
|
||||
NoExpiry = time.Duration(0)
|
||||
|
||||
// DefaultExpiry represents 1 hour time duration when all entries shall be expired.
|
||||
DefaultExpiry = time.Hour
|
||||
|
||||
// defaultBufferRatio represents default ratio used to calculate the
|
||||
// individual cache entry buffer size.
|
||||
defaultBufferRatio = uint64(10)
|
||||
)
|
||||
|
||||
var (
|
||||
// ErrKeyNotFoundInCache - key not found in cache.
|
||||
ErrKeyNotFoundInCache = errors.New("Key not found in cache")
|
||||
|
||||
// ErrCacheFull - cache is full.
|
||||
ErrCacheFull = errors.New("Not enough space in cache")
|
||||
|
||||
// ErrExcessData - excess data was attempted to be written on cache.
|
||||
ErrExcessData = errors.New("Attempted excess write on cache")
|
||||
)
|
||||
|
||||
// buffer represents the in memory cache of a single entry.
|
||||
// buffer carries value of the data and last accessed time.
|
||||
type buffer struct {
|
||||
buf *bytebufferpool.ByteBuffer
|
||||
lastAccessed time.Time // Represents time when value was last accessed.
|
||||
}
|
||||
|
||||
// Cache holds the required variables to compose an in memory cache system
|
||||
// which also provides expiring key mechanism and also maxSize.
|
||||
type Cache struct {
|
||||
// Mutex is used for handling the concurrent
|
||||
// read/write requests for cache
|
||||
mutex sync.Mutex
|
||||
|
||||
// Once is used for resetting GC once after
|
||||
// peak cache usage.
|
||||
onceGC sync.Once
|
||||
|
||||
// maxSize is a total size for overall cache
|
||||
maxSize uint64
|
||||
|
||||
// maxCacheEntrySize is a total size per key buffer.
|
||||
maxCacheEntrySize uint64
|
||||
|
||||
// currentSize is a current size in memory
|
||||
currentSize uint64
|
||||
|
||||
// OnEviction - callback function for eviction
|
||||
OnEviction func(key string)
|
||||
|
||||
// totalEvicted counter to keep track of total expirys
|
||||
totalEvicted int
|
||||
|
||||
// map of cached keys and its values
|
||||
entries map[string]*buffer
|
||||
|
||||
// Expiry in time duration.
|
||||
expiry time.Duration
|
||||
|
||||
// Stop garbage collection routine, stops any running GC routine.
|
||||
stopGC chan struct{}
|
||||
}
|
||||
|
||||
// New - Return a new cache with a given default expiry
|
||||
// duration. If the expiry duration is less than one
|
||||
// (or NoExpiry), the items in the cache never expire
|
||||
// (by default), and must be deleted manually.
|
||||
func New(maxSize uint64, expiry time.Duration) (c *Cache, err error) {
|
||||
if maxSize == 0 {
|
||||
err = errors.New("invalid maximum cache size")
|
||||
return c, err
|
||||
}
|
||||
|
||||
// Max cache entry size - indicates the
|
||||
// maximum buffer per key that can be held in
|
||||
// memory. Currently this value is 1/10th
|
||||
// the size of requested cache size.
|
||||
maxCacheEntrySize := func() uint64 {
|
||||
i := maxSize / defaultBufferRatio
|
||||
if i == 0 {
|
||||
i = maxSize
|
||||
}
|
||||
return i
|
||||
}()
|
||||
|
||||
c = &Cache{
|
||||
onceGC: sync.Once{},
|
||||
maxSize: maxSize,
|
||||
maxCacheEntrySize: maxCacheEntrySize,
|
||||
entries: make(map[string]*buffer),
|
||||
expiry: expiry,
|
||||
}
|
||||
|
||||
// We have expiry start the janitor routine.
|
||||
if expiry > 0 {
|
||||
// Initialize a new stop GC channel.
|
||||
c.stopGC = make(chan struct{})
|
||||
|
||||
// Start garbage collection routine to expire objects.
|
||||
c.StartGC()
|
||||
}
|
||||
|
||||
return c, nil
|
||||
}
|
||||
|
||||
// Create - validates if object size fits with in cache size limit and returns a io.WriteCloser
|
||||
// to which object contents can be written and finally Close()'d. During Close() we
|
||||
// checks if the amount of data written is equal to the size of the object, in which
|
||||
// case it saves the contents to object cache.
|
||||
func (c *Cache) Create(key string) (wc io.WriteCloser) {
|
||||
buf := bytebufferpool.Get()
|
||||
|
||||
// Function called on close which saves the object contents
|
||||
// to the object cache.
|
||||
onClose := func() error {
|
||||
c.mutex.Lock()
|
||||
defer c.mutex.Unlock()
|
||||
|
||||
if buf.Len() == 0 {
|
||||
buf.Reset()
|
||||
bytebufferpool.Put(buf)
|
||||
|
||||
// If nothing is written in the buffer
|
||||
// the key is not stored.
|
||||
return nil
|
||||
}
|
||||
|
||||
if uint64(buf.Len()) > c.maxCacheEntrySize {
|
||||
buf.Reset()
|
||||
bytebufferpool.Put(buf)
|
||||
|
||||
return ErrCacheFull
|
||||
}
|
||||
|
||||
// Full object available in buf, save it to cache.
|
||||
c.entries[key] = &buffer{
|
||||
buf: buf,
|
||||
lastAccessed: time.Now().UTC(), // Save last accessed time.
|
||||
}
|
||||
|
||||
// Account for the memory allocated above.
|
||||
c.currentSize += uint64(buf.Len())
|
||||
return nil
|
||||
}
|
||||
|
||||
return &writeCloser{ByteBuffer: buf, onClose: onClose}
|
||||
}
|
||||
|
||||
// Open - open the in-memory file, returns an in memory reader.
|
||||
// returns an error ErrKeyNotFoundInCache, if the key does not
|
||||
// exist. ErrKeyNotFoundInCache is also returned if lastAccessed
|
||||
// is older than input atime.
|
||||
func (c *Cache) Open(key string, atime time.Time) (io.Reader, error) {
|
||||
// Entry exists, return the readable buffer.
|
||||
c.mutex.Lock()
|
||||
defer c.mutex.Unlock()
|
||||
b, ok := c.entries[key]
|
||||
if !ok {
|
||||
return nil, ErrKeyNotFoundInCache
|
||||
}
|
||||
|
||||
// Check if buf was recently accessed.
|
||||
if b.lastAccessed.Before(atime) {
|
||||
c.delete(key)
|
||||
return nil, ErrKeyNotFoundInCache
|
||||
}
|
||||
|
||||
b.lastAccessed = time.Now()
|
||||
return bytes.NewReader(b.buf.Bytes()), nil
|
||||
}
|
||||
|
||||
// Delete - delete deletes an entry from the cache.
|
||||
func (c *Cache) Delete(key string) {
|
||||
c.mutex.Lock()
|
||||
c.delete(key)
|
||||
c.mutex.Unlock()
|
||||
if c.OnEviction != nil {
|
||||
c.OnEviction(key)
|
||||
}
|
||||
}
|
||||
|
||||
// gc - garbage collect all the expired entries from the cache.
|
||||
func (c *Cache) gc() {
|
||||
var evictedEntries []string
|
||||
c.mutex.Lock()
|
||||
for k, v := range c.entries {
|
||||
if c.expiry > 0 && time.Now().UTC().Sub(v.lastAccessed) > c.expiry {
|
||||
c.delete(k)
|
||||
evictedEntries = append(evictedEntries, k)
|
||||
}
|
||||
}
|
||||
c.mutex.Unlock()
|
||||
for _, k := range evictedEntries {
|
||||
if c.OnEviction != nil {
|
||||
c.OnEviction(k)
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// StopGC sends a message to the expiry routine to stop
|
||||
// expiring cached entries. NOTE: once this is called, cached
|
||||
// entries will not be expired, be careful if you are using this.
|
||||
func (c *Cache) StopGC() {
|
||||
if c.stopGC != nil {
|
||||
c.stopGC <- struct{}{}
|
||||
}
|
||||
}
|
||||
|
||||
// StartGC starts running a routine ticking at expiry interval,
|
||||
// on each interval this routine does a sweep across the cache
|
||||
// entries and garbage collects all the expired entries.
|
||||
func (c *Cache) StartGC() {
|
||||
go func() {
|
||||
for {
|
||||
select {
|
||||
// Wait till cleanup interval and initiate delete expired entries.
|
||||
case <-time.After(c.expiry / 4):
|
||||
c.gc()
|
||||
// Stop the routine, usually called by the user of object cache during cleanup.
|
||||
case <-c.stopGC:
|
||||
return
|
||||
}
|
||||
}
|
||||
}()
|
||||
}
|
||||
|
||||
// Deletes a requested entry from the cache.
|
||||
func (c *Cache) delete(key string) {
|
||||
if _, ok := c.entries[key]; ok {
|
||||
deletedSize := uint64(c.entries[key].buf.Len())
|
||||
c.entries[key].buf.Reset()
|
||||
bytebufferpool.Put(c.entries[key].buf)
|
||||
delete(c.entries, key)
|
||||
c.currentSize -= deletedSize
|
||||
c.totalEvicted++
|
||||
}
|
||||
}
|
||||
309
pkg/objcache/objcache_test.go
Normal file
309
pkg/objcache/objcache_test.go
Normal file
@@ -0,0 +1,309 @@
|
||||
/*
|
||||
* Minio Cloud Storage, (C) 2021 Minio, 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 objcache
|
||||
|
||||
import (
|
||||
"bytes"
|
||||
"io"
|
||||
"testing"
|
||||
"time"
|
||||
)
|
||||
|
||||
// TestObjectCache tests cases of object cache with expiry.
|
||||
func TestObjExpiry(t *testing.T) {
|
||||
// Non exhaustive list of all object cache behavior cases.
|
||||
testCases := []struct {
|
||||
expiry time.Duration
|
||||
cacheSize uint64
|
||||
err error
|
||||
closeErr error
|
||||
}{
|
||||
{
|
||||
expiry: 100 * time.Millisecond,
|
||||
cacheSize: 1024,
|
||||
err: ErrKeyNotFoundInCache,
|
||||
closeErr: nil,
|
||||
},
|
||||
}
|
||||
|
||||
// Test case 1 validates running of GC.
|
||||
testCase := testCases[0]
|
||||
cache, err := New(testCase.cacheSize, testCase.expiry)
|
||||
if err != nil {
|
||||
t.Fatalf("Unable to create new objcache")
|
||||
}
|
||||
|
||||
cache.OnEviction = func(key string) {}
|
||||
w := cache.Create("test")
|
||||
// Write a byte.
|
||||
w.Write([]byte("1"))
|
||||
if err = w.Close(); err != nil {
|
||||
t.Errorf("Test case 1 expected to pass, failed instead %s", err)
|
||||
}
|
||||
// Wait for 500 millisecond.
|
||||
time.Sleep(500 * time.Millisecond)
|
||||
// Setting objModTime to the beginning of golang's time.Time to avoid deletion of stale entry.
|
||||
fakeObjModTime := time.Time{}
|
||||
_, err = cache.Open("test", fakeObjModTime)
|
||||
if err != testCase.err {
|
||||
t.Errorf("Test case 1 expected %s, got instead %s", testCase.err, err)
|
||||
}
|
||||
}
|
||||
|
||||
// TestObjCache - tests various cases for object cache behavior.
|
||||
func TestObjCache(t *testing.T) {
|
||||
// Setting objModTime to the beginning of golang's time.Time to avoid deletion of stale entry.
|
||||
fakeObjModTime := time.Time{}
|
||||
|
||||
// Non exhaustive list of all object cache behavior cases.
|
||||
testCases := []struct {
|
||||
expiry time.Duration
|
||||
cacheSize uint64
|
||||
err error
|
||||
closeErr error
|
||||
}{
|
||||
// Validate if a key is not found in cache and Open fails.
|
||||
{
|
||||
expiry: NoExpiry,
|
||||
cacheSize: 1024,
|
||||
err: ErrKeyNotFoundInCache,
|
||||
},
|
||||
// Validate if cache indicates that it is full and Create fails.
|
||||
{
|
||||
expiry: NoExpiry,
|
||||
cacheSize: 1,
|
||||
err: ErrCacheFull,
|
||||
},
|
||||
// Validate if Create succeeds but Close fails to write to buffer.
|
||||
{
|
||||
expiry: NoExpiry,
|
||||
cacheSize: 2,
|
||||
closeErr: io.ErrShortBuffer,
|
||||
},
|
||||
// Validate that Create and Close succeed, making sure to update the cache.
|
||||
{
|
||||
expiry: NoExpiry,
|
||||
cacheSize: 1024,
|
||||
},
|
||||
// Validate that Delete succeeds and Open fails with key not found in cache.
|
||||
{
|
||||
expiry: NoExpiry,
|
||||
cacheSize: 1024,
|
||||
err: ErrKeyNotFoundInCache,
|
||||
},
|
||||
// Validate OnEviction function is called upon entry delete.
|
||||
{
|
||||
expiry: NoExpiry,
|
||||
cacheSize: 1024,
|
||||
},
|
||||
// Validate error excess data.
|
||||
{
|
||||
expiry: NoExpiry,
|
||||
cacheSize: 5,
|
||||
closeErr: ErrExcessData,
|
||||
},
|
||||
// Validate error excess data during write.
|
||||
{
|
||||
expiry: NoExpiry,
|
||||
cacheSize: 2048,
|
||||
err: ErrExcessData,
|
||||
},
|
||||
}
|
||||
|
||||
// Test 1 validating Open failure.
|
||||
testCase := testCases[0]
|
||||
cache, err := New(testCase.cacheSize, testCase.expiry)
|
||||
if err != nil {
|
||||
t.Fatalf("Unable to create new objcache")
|
||||
}
|
||||
|
||||
_, err = cache.Open("test", fakeObjModTime)
|
||||
if testCase.err != err {
|
||||
t.Errorf("Test case 2 expected to pass, failed instead %s", err)
|
||||
}
|
||||
|
||||
// Test 2 validating Create failure.
|
||||
testCase = testCases[1]
|
||||
cache, err = New(testCase.cacheSize, testCase.expiry)
|
||||
if err != nil {
|
||||
t.Fatalf("Unable to create new objcache")
|
||||
}
|
||||
|
||||
w := cache.Create("test")
|
||||
if w == nil {
|
||||
t.Errorf("Test case 2 expected to pass, but returned nil")
|
||||
}
|
||||
w.Close()
|
||||
|
||||
// Test 3 validating Create succeeds and returns a writer.
|
||||
// Subsequently we Close() without writing any data, to receive
|
||||
// `io.ErrShortBuffer`
|
||||
testCase = testCases[2]
|
||||
cache, err = New(testCase.cacheSize, testCase.expiry)
|
||||
if err != nil {
|
||||
t.Fatalf("Unable to create new objcache")
|
||||
}
|
||||
|
||||
w = cache.Create("test")
|
||||
// nothing is stored in the key, upon Close() the buf is discarded.
|
||||
if err = w.Close(); err != nil {
|
||||
t.Errorf("Test case 3 expected to pass, failed instead %s", err)
|
||||
}
|
||||
|
||||
// Test 4 validates Create and Close succeeds successfully caching
|
||||
// the writes.
|
||||
testCase = testCases[3]
|
||||
cache, err = New(testCase.cacheSize, testCase.expiry)
|
||||
if err != nil {
|
||||
t.Fatalf("Unable to create new objcache")
|
||||
}
|
||||
|
||||
w = cache.Create("test")
|
||||
// Write '5' bytes.
|
||||
w.Write([]byte("Hello"))
|
||||
// Close to successfully save into cache.
|
||||
if err = w.Close(); err != nil {
|
||||
t.Errorf("Test case 4 expected to pass, failed instead %s", err)
|
||||
}
|
||||
r, err := cache.Open("test", fakeObjModTime)
|
||||
if err != nil {
|
||||
t.Errorf("Test case 4 expected to pass, failed instead %s", err)
|
||||
}
|
||||
// Reads everything stored for key "test".
|
||||
cbytes := make([]byte, 5)
|
||||
rat := r.(io.ReaderAt)
|
||||
_, err = rat.ReadAt(cbytes, 0)
|
||||
if err != nil {
|
||||
t.Errorf("Test case 4 expected to pass, failed instead %s", err)
|
||||
}
|
||||
// Validate if read bytes match.
|
||||
if !bytes.Equal(cbytes, []byte("Hello")) {
|
||||
t.Errorf("Test case 4 expected to pass. wanted \"Hello\", got %s", string(cbytes))
|
||||
}
|
||||
|
||||
// Test 5 validates Delete succeeds and Open fails with err
|
||||
testCase = testCases[4]
|
||||
cache, err = New(testCase.cacheSize, testCase.expiry)
|
||||
if err != nil {
|
||||
t.Fatalf("Unable to create new objcache")
|
||||
}
|
||||
|
||||
w = cache.Create("test")
|
||||
// Write '5' bytes.
|
||||
w.Write([]byte("Hello"))
|
||||
// Close to successfully save into cache.
|
||||
if err = w.Close(); err != nil {
|
||||
t.Errorf("Test case 5 expected to pass, failed instead %s", err)
|
||||
}
|
||||
// Delete the cache entry.
|
||||
cache.Delete("test")
|
||||
_, err = cache.Open("test", fakeObjModTime)
|
||||
if testCase.err != err {
|
||||
t.Errorf("Test case 5 expected to pass, failed instead %s", err)
|
||||
}
|
||||
|
||||
// Test 6 validates OnEviction being called upon Delete is being invoked.
|
||||
testCase = testCases[5]
|
||||
cache, err = New(testCase.cacheSize, testCase.expiry)
|
||||
if err != nil {
|
||||
t.Fatalf("Unable to create new objcache")
|
||||
}
|
||||
|
||||
w = cache.Create("test")
|
||||
// Write '5' bytes.
|
||||
w.Write([]byte("Hello"))
|
||||
// Close to successfully save into cache.
|
||||
if err = w.Close(); err != nil {
|
||||
t.Errorf("Test case 6 expected to pass, failed instead %s", err)
|
||||
}
|
||||
var deleteKey string
|
||||
cache.OnEviction = func(key string) {
|
||||
deleteKey = key
|
||||
}
|
||||
// Delete the cache entry.
|
||||
cache.Delete("test")
|
||||
if deleteKey != "test" {
|
||||
t.Errorf("Test case 6 expected to pass, wanted \"test\", got %s", deleteKey)
|
||||
}
|
||||
|
||||
// Test 7 validates rejecting requests when excess data is being saved.
|
||||
testCase = testCases[6]
|
||||
cache, err = New(testCase.cacheSize, testCase.expiry)
|
||||
if err != nil {
|
||||
t.Fatalf("Unable to create new objcache")
|
||||
}
|
||||
|
||||
w = cache.Create("test1")
|
||||
// Write '5' bytes.
|
||||
w.Write([]byte("Hello"))
|
||||
// Close to successfully save into cache.
|
||||
if err = w.Close(); err != nil {
|
||||
t.Errorf("Test case 7 expected to pass, failed instead %s", err)
|
||||
}
|
||||
|
||||
w = cache.Create("test2")
|
||||
// nothing got written, Close() will return success.
|
||||
if err = w.Close(); err != nil {
|
||||
t.Errorf("Test case 7 expected to pass, failed instead %s", err)
|
||||
}
|
||||
|
||||
// Test 8 validates rejecting Writes which write excess data.
|
||||
testCase = testCases[7]
|
||||
cache, err = New(testCase.cacheSize, testCase.expiry)
|
||||
if err != nil {
|
||||
t.Fatalf("Unable to create new objcache")
|
||||
}
|
||||
|
||||
w = cache.Create("test1")
|
||||
defer w.Close()
|
||||
|
||||
// Write '5' bytes.
|
||||
n, err := w.Write([]byte("Hello"))
|
||||
if err != nil {
|
||||
t.Errorf("Test case 8 expected to pass, failed instead %s", err)
|
||||
}
|
||||
if n != 5 {
|
||||
t.Errorf("Test case 8 expected 5 bytes written, instead found %d", n)
|
||||
}
|
||||
// Write '1' more byte, should return error.
|
||||
n, err = w.Write([]byte("W"))
|
||||
if n == 0 && err != testCase.err {
|
||||
t.Errorf("Test case 8 expected to fail with ErrExcessData, but failed with %s instead", err)
|
||||
}
|
||||
}
|
||||
|
||||
// TestStateEntryPurge - tests if objCache purges stale entry and returns ErrKeyNotFoundInCache.
|
||||
func TestStaleEntryPurge(t *testing.T) {
|
||||
cache, err := New(1024, NoExpiry)
|
||||
if err != nil {
|
||||
t.Fatalf("Unable to create new objcache")
|
||||
}
|
||||
|
||||
w := cache.Create("test")
|
||||
// Write '5' bytes.
|
||||
w.Write([]byte("Hello"))
|
||||
// Close to successfully save into cache.
|
||||
if err = w.Close(); err != nil {
|
||||
t.Errorf("Test case expected to pass, failed instead %s", err)
|
||||
}
|
||||
|
||||
_, err = cache.Open("test", time.Now().AddDate(0, 0, 1).UTC())
|
||||
if err != ErrKeyNotFoundInCache {
|
||||
t.Errorf("Test case expected to return ErrKeyNotFoundInCache, instead returned %s", err)
|
||||
}
|
||||
}
|
||||
34
pkg/objcache/write_closer.go
Normal file
34
pkg/objcache/write_closer.go
Normal file
@@ -0,0 +1,34 @@
|
||||
/*
|
||||
* Minio Cloud Storage, (C) 2021 Minio, 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 objcache implements in memory caching methods.
|
||||
package objcache
|
||||
|
||||
import "github.com/valyala/bytebufferpool"
|
||||
|
||||
// Is an Closer wrapper for bytebufferpool, upon close
|
||||
// calls the defined onClose function.
|
||||
type writeCloser struct {
|
||||
*bytebufferpool.ByteBuffer
|
||||
onClose func() error
|
||||
}
|
||||
|
||||
// On close, onClose() is called which checks if all object contents
|
||||
// have been written so that it can save the buffer to the cache.
|
||||
func (c writeCloser) Close() (err error) {
|
||||
return c.onClose()
|
||||
}
|
||||
Reference in New Issue
Block a user