/
cache.go
167 lines (143 loc) · 4.01 KB
/
cache.go
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package pebble
import (
"errors"
"fmt"
lru "github.com/hashicorp/golang-lru/v2"
"github.com/onflow/flow-go/model/flow"
"github.com/onflow/flow-go/module"
"github.com/onflow/flow-go/storage"
)
const DefaultCacheSize = uint(10_000)
type CacheType int
const (
CacheTypeLRU CacheType = iota + 1
CacheTypeTwoQueue
)
func ParseCacheType(s string) (CacheType, error) {
switch s {
case CacheTypeLRU.String():
return CacheTypeLRU, nil
case CacheTypeTwoQueue.String():
return CacheTypeTwoQueue, nil
default:
return 0, errors.New("invalid cache type")
}
}
func (m CacheType) String() string {
switch m {
case CacheTypeLRU:
return "lru"
case CacheTypeTwoQueue:
return "2q"
default:
return ""
}
}
type CacheBackend interface {
Get(key string) (value flow.RegisterValue, ok bool)
Add(key string, value flow.RegisterValue)
Contains(key string) bool
Len() int
Remove(key string)
}
// wrapped is a wrapper around lru.Cache to implement CacheBackend
// this is needed because the standard lru cache implementation provides additional features that
// the 2Q cache do not. This standardizes the interface to allow swapping between types.
type wrapped struct {
cache *lru.Cache[string, flow.RegisterValue]
}
func (c *wrapped) Get(key string) (value flow.RegisterValue, ok bool) {
return c.cache.Get(key)
}
func (c *wrapped) Add(key string, value flow.RegisterValue) {
_ = c.cache.Add(key, value)
}
func (c *wrapped) Contains(key string) bool {
return c.cache.Contains(key)
}
func (c *wrapped) Len() int {
return c.cache.Len()
}
func (c *wrapped) Remove(key string) {
_ = c.cache.Remove(key)
}
type ReadCache struct {
metrics module.CacheMetrics
resource string
cache CacheBackend
retrieve func(key string) (flow.RegisterValue, error)
}
func newReadCache(
collector module.CacheMetrics,
resourceName string,
cacheType CacheType,
cacheSize uint,
retrieve func(key string) (flow.RegisterValue, error),
) (*ReadCache, error) {
cache, err := getCache(cacheType, int(cacheSize))
if err != nil {
return nil, fmt.Errorf("could not create cache: %w", err)
}
c := ReadCache{
metrics: collector,
resource: resourceName,
cache: cache,
retrieve: retrieve,
}
c.metrics.CacheEntries(c.resource, uint(c.cache.Len()))
return &c, nil
}
func getCache(cacheType CacheType, size int) (CacheBackend, error) {
switch cacheType {
case CacheTypeLRU:
cache, err := lru.New[string, flow.RegisterValue](size)
if err != nil {
return nil, err
}
return &wrapped{cache: cache}, nil
case CacheTypeTwoQueue:
return lru.New2Q[string, flow.RegisterValue](size)
default:
return nil, fmt.Errorf("unknown cache type: %d", cacheType)
}
}
// IsCached returns true if the key exists in the cache.
// It DOES NOT check whether the key exists in the underlying data store.
func (c *ReadCache) IsCached(key string) bool {
return c.cache.Contains(key)
}
// Get will try to retrieve the resource from cache first, and then from the
// injected. During normal operations, the following error returns are expected:
// - `storage.ErrNotFound` if key is unknown.
func (c *ReadCache) Get(key string) (flow.RegisterValue, error) {
resource, cached := c.cache.Get(key)
if cached {
c.metrics.CacheHit(c.resource)
if resource == nil {
return nil, storage.ErrNotFound
}
return resource, nil
}
// get it from the database
resource, err := c.retrieve(key)
if err != nil {
if errors.Is(err, storage.ErrNotFound) {
c.cache.Add(key, nil)
c.metrics.CacheEntries(c.resource, uint(c.cache.Len()))
c.metrics.CacheNotFound(c.resource)
}
return nil, fmt.Errorf("could not retrieve resource: %w", err)
}
c.metrics.CacheMiss(c.resource)
c.cache.Add(key, resource)
c.metrics.CacheEntries(c.resource, uint(c.cache.Len()))
return resource, nil
}
func (c *ReadCache) Remove(key string) {
c.cache.Remove(key)
}
// Insert will add a resource directly to the cache with the given ID
func (c *ReadCache) Insert(key string, resource flow.RegisterValue) {
c.cache.Add(key, resource)
c.metrics.CacheEntries(c.resource, uint(c.cache.Len()))
}