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cache.go
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cache.go
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package badger
import (
"errors"
"fmt"
"github.com/dgraph-io/badger/v2"
lru "github.com/hashicorp/golang-lru/v2"
"github.com/onflow/flow-go/module"
"github.com/onflow/flow-go/storage"
"github.com/onflow/flow-go/storage/badger/transaction"
)
func withLimit[K comparable, V any](limit uint) func(*Cache[K, V]) {
return func(c *Cache[K, V]) {
c.limit = limit
}
}
type storeFunc[K comparable, V any] func(key K, val V) func(*transaction.Tx) error
const DefaultCacheSize = uint(1000)
func withStore[K comparable, V any](store storeFunc[K, V]) func(*Cache[K, V]) {
return func(c *Cache[K, V]) {
c.store = store
}
}
func noStore[K comparable, V any](_ K, _ V) func(*transaction.Tx) error {
return func(tx *transaction.Tx) error {
return fmt.Errorf("no store function for cache put available")
}
}
func noopStore[K comparable, V any](_ K, _ V) func(*transaction.Tx) error {
return func(tx *transaction.Tx) error {
return nil
}
}
type retrieveFunc[K comparable, V any] func(key K) func(*badger.Txn) (V, error)
func withRetrieve[K comparable, V any](retrieve retrieveFunc[K, V]) func(*Cache[K, V]) {
return func(c *Cache[K, V]) {
c.retrieve = retrieve
}
}
func noRetrieve[K comparable, V any](_ K) func(*badger.Txn) (V, error) {
return func(tx *badger.Txn) (V, error) {
var nullV V
return nullV, fmt.Errorf("no retrieve function for cache get available")
}
}
type Cache[K comparable, V any] struct {
metrics module.CacheMetrics
limit uint
store storeFunc[K, V]
retrieve retrieveFunc[K, V]
resource string
cache *lru.Cache[K, V]
}
func newCache[K comparable, V any](collector module.CacheMetrics, resourceName string, options ...func(*Cache[K, V])) *Cache[K, V] {
c := Cache[K, V]{
metrics: collector,
limit: 1000,
store: noStore[K, V],
retrieve: noRetrieve[K, V],
resource: resourceName,
}
for _, option := range options {
option(&c)
}
c.cache, _ = lru.New[K, V](int(c.limit))
c.metrics.CacheEntries(c.resource, uint(c.cache.Len()))
return &c
}
// 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 *Cache[K, V]) IsCached(key K) 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 *Cache[K, V]) Get(key K) func(*badger.Txn) (V, error) {
return func(tx *badger.Txn) (V, error) {
// check if we have it in the cache
resource, cached := c.cache.Get(key)
if cached {
c.metrics.CacheHit(c.resource)
return resource, nil
}
// get it from the database
resource, err := c.retrieve(key)(tx)
if err != nil {
if errors.Is(err, storage.ErrNotFound) {
c.metrics.CacheNotFound(c.resource)
}
var nullV V
return nullV, fmt.Errorf("could not retrieve resource: %w", err)
}
c.metrics.CacheMiss(c.resource)
// cache the resource and eject least recently used one if we reached limit
evicted := c.cache.Add(key, resource)
if !evicted {
c.metrics.CacheEntries(c.resource, uint(c.cache.Len()))
}
return resource, nil
}
}
func (c *Cache[K, V]) Remove(key K) {
c.cache.Remove(key)
}
// Insert will add a resource directly to the cache with the given ID
func (c *Cache[K, V]) Insert(key K, resource V) {
// cache the resource and eject least recently used one if we reached limit
evicted := c.cache.Add(key, resource)
if !evicted {
c.metrics.CacheEntries(c.resource, uint(c.cache.Len()))
}
}
// PutTx will return tx which adds a resource to the cache with the given ID.
func (c *Cache[K, V]) PutTx(key K, resource V) func(*transaction.Tx) error {
storeOps := c.store(key, resource) // assemble DB operations to store resource (no execution)
return func(tx *transaction.Tx) error {
err := storeOps(tx) // execute operations to store resource
if err != nil {
return fmt.Errorf("could not store resource: %w", err)
}
tx.OnSucceed(func() {
c.Insert(key, resource)
})
return nil
}
}