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package log_buffer
import (
"container/list"
"sync"
"time"
"github.com/seaweedfs/seaweedfs/weed/glog"
)
// DiskBufferCache is a small LRU cache for recently-read historical data buffers
// This reduces Filer load when multiple consumers are catching up on historical messages
type DiskBufferCache struct {
maxSize int
ttl time.Duration
cache map[string]*cacheEntry
lruList *list.List
mu sync.RWMutex
hits int64
misses int64
evictions int64
}
type cacheEntry struct {
key string
data []byte
offset int64
timestamp time.Time
lruElement *list.Element
isNegative bool // true if this is a negative cache entry (data not found)
}
// NewDiskBufferCache creates a new cache with the specified size and TTL
// Recommended size: 3-5 buffers (each ~8MB)
// Recommended TTL: 30-60 seconds
func NewDiskBufferCache(maxSize int, ttl time.Duration) *DiskBufferCache {
cache := &DiskBufferCache{
maxSize: maxSize,
ttl: ttl,
cache: make(map[string]*cacheEntry),
lruList: list.New(),
}
// Start background cleanup goroutine
go cache.cleanupLoop()
return cache
}
// Get retrieves a buffer from the cache
// Returns (data, offset, found)
// If found=true and data=nil, this is a negative cache entry (data doesn't exist)
func (c *DiskBufferCache) Get(key string) ([]byte, int64, bool) {
c.mu.Lock()
defer c.mu.Unlock()
entry, exists := c.cache[key]
if !exists {
c.misses++
return nil, 0, false
}
// Check if entry has expired
if time.Since(entry.timestamp) > c.ttl {
c.evict(entry)
c.misses++
return nil, 0, false
}
// Move to front of LRU list (most recently used)
c.lruList.MoveToFront(entry.lruElement)
c.hits++
if entry.isNegative {
glog.V(4).Infof("📦 CACHE HIT (NEGATIVE): key=%s - data not found (hits=%d misses=%d)",
key, c.hits, c.misses)
} else {
glog.V(4).Infof("📦 CACHE HIT: key=%s offset=%d size=%d (hits=%d misses=%d)",
key, entry.offset, len(entry.data), c.hits, c.misses)
}
return entry.data, entry.offset, true
}
// Put adds a buffer to the cache
// If data is nil, this creates a negative cache entry (data doesn't exist)
func (c *DiskBufferCache) Put(key string, data []byte, offset int64) {
c.mu.Lock()
defer c.mu.Unlock()
isNegative := data == nil
// Check if entry already exists
if entry, exists := c.cache[key]; exists {
// Update existing entry
entry.data = data
entry.offset = offset
entry.timestamp = time.Now()
entry.isNegative = isNegative
c.lruList.MoveToFront(entry.lruElement)
if isNegative {
glog.V(4).Infof("📦 CACHE UPDATE (NEGATIVE): key=%s - data not found", key)
} else {
glog.V(4).Infof("📦 CACHE UPDATE: key=%s offset=%d size=%d", key, offset, len(data))
}
return
}
// Evict oldest entry if cache is full
if c.lruList.Len() >= c.maxSize {
oldest := c.lruList.Back()
if oldest != nil {
c.evict(oldest.Value.(*cacheEntry))
}
}
// Add new entry
entry := &cacheEntry{
key: key,
data: data,
offset: offset,
timestamp: time.Now(),
isNegative: isNegative,
}
entry.lruElement = c.lruList.PushFront(entry)
c.cache[key] = entry
if isNegative {
glog.V(4).Infof("📦 CACHE PUT (NEGATIVE): key=%s - data not found (cache_size=%d/%d)",
key, c.lruList.Len(), c.maxSize)
} else {
glog.V(4).Infof("📦 CACHE PUT: key=%s offset=%d size=%d (cache_size=%d/%d)",
key, offset, len(data), c.lruList.Len(), c.maxSize)
}
}
// evict removes an entry from the cache (must be called with lock held)
func (c *DiskBufferCache) evict(entry *cacheEntry) {
delete(c.cache, entry.key)
c.lruList.Remove(entry.lruElement)
c.evictions++
glog.V(4).Infof("📦 CACHE EVICT: key=%s (evictions=%d)", entry.key, c.evictions)
}
// cleanupLoop periodically removes expired entries
func (c *DiskBufferCache) cleanupLoop() {
ticker := time.NewTicker(c.ttl / 2)
defer ticker.Stop()
for range ticker.C {
c.cleanup()
}
}
// cleanup removes expired entries
func (c *DiskBufferCache) cleanup() {
c.mu.Lock()
defer c.mu.Unlock()
now := time.Now()
var toEvict []*cacheEntry
// Find expired entries
for _, entry := range c.cache {
if now.Sub(entry.timestamp) > c.ttl {
toEvict = append(toEvict, entry)
}
}
// Evict expired entries
for _, entry := range toEvict {
c.evict(entry)
}
if len(toEvict) > 0 {
glog.V(3).Infof("📦 CACHE CLEANUP: evicted %d expired entries", len(toEvict))
}
}
// Stats returns cache statistics
func (c *DiskBufferCache) Stats() (hits, misses, evictions int64, size int) {
c.mu.RLock()
defer c.mu.RUnlock()
return c.hits, c.misses, c.evictions, c.lruList.Len()
}
// Clear removes all entries from the cache
func (c *DiskBufferCache) Clear() {
c.mu.Lock()
defer c.mu.Unlock()
c.cache = make(map[string]*cacheEntry)
c.lruList = list.New()
glog.V(2).Infof("📦 CACHE CLEARED")
}
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