frostfs-node/pkg/local_object_storage/blobstor/blobovniczatree/cache.go

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package blobovniczatree
import (
"fmt"
"sync"
utilSync "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util/sync"
"github.com/hashicorp/golang-lru/v2/simplelru"
)
// dbCache caches sharedDB instances that are NOT open for Put.
//
// Uses dbManager for opening/closing sharedDB instances.
// Stores a reference to an cached sharedDB, so dbManager does not close it.
type dbCache struct {
cacheGuard *sync.RWMutex
cache simplelru.LRUCache[string, *sharedDB]
pathLock *utilSync.KeyLocker[string] // the order of locks is important: pathLock first, cacheGuard second
closed bool
nonCached map[string]struct{}
dbManager *dbManager
}
func newDBCache(size int, dbManager *dbManager) *dbCache {
cache, err := simplelru.NewLRU[string, *sharedDB](size, func(_ string, evictedDB *sharedDB) {
evictedDB.Close()
})
if err != nil {
// occurs only if the size is not positive
panic(fmt.Errorf("could not create LRU cache of size %d: %w", size, err))
}
return &dbCache{
cacheGuard: &sync.RWMutex{},
cache: cache,
dbManager: dbManager,
pathLock: utilSync.NewKeyLocker[string](),
nonCached: make(map[string]struct{}),
}
}
func (c *dbCache) Open() {
c.cacheGuard.Lock()
defer c.cacheGuard.Unlock()
c.closed = false
}
func (c *dbCache) Close() {
c.cacheGuard.Lock()
defer c.cacheGuard.Unlock()
c.cache.Purge()
c.closed = true
}
func (c *dbCache) GetOrCreate(path string) *sharedDB {
value := c.getExisted(path)
if value != nil {
return value
}
return c.create(path)
}
func (c *dbCache) EvictAndMarkNonCached(path string) {
c.pathLock.Lock(path)
defer c.pathLock.Unlock(path)
c.cacheGuard.Lock()
defer c.cacheGuard.Unlock()
c.cache.Remove(path)
c.nonCached[path] = struct{}{}
}
func (c *dbCache) RemoveFromNonCached(path string) {
c.pathLock.Lock(path)
defer c.pathLock.Unlock(path)
c.cacheGuard.Lock()
defer c.cacheGuard.Unlock()
delete(c.nonCached, path)
}
func (c *dbCache) getExisted(path string) *sharedDB {
c.cacheGuard.Lock()
defer c.cacheGuard.Unlock()
if value, ok := c.cache.Get(path); ok {
return value
}
return nil
}
func (c *dbCache) create(path string) *sharedDB {
c.pathLock.Lock(path)
defer c.pathLock.Unlock(path)
value := c.getExisted(path)
if value != nil {
return value
}
value = c.dbManager.GetByPath(path)
_, err := value.Open() // open db to hold reference, closed by evictedDB.Close() or if cache closed
if err != nil {
return value
}
if added := c.put(path, value); !added {
value.Close()
}
return value
}
func (c *dbCache) put(path string, db *sharedDB) bool {
c.cacheGuard.Lock()
defer c.cacheGuard.Unlock()
_, isNonCached := c.nonCached[path]
if !isNonCached && !c.closed {
c.cache.Add(path, db)
return true
}
return false
}