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chain.go
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chain.go
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package kvstore
import (
"context"
"fmt"
"reflect"
"github.com/justtrackio/gosoline/pkg/cfg"
"github.com/justtrackio/gosoline/pkg/log"
"github.com/justtrackio/gosoline/pkg/refl"
)
type ChainKvStore[T any] interface {
KvStore[T]
Add(elementFactory ElementFactory[T]) error
AddStore(store KvStore[T])
}
type chainKvStore[T any] struct {
logger log.Logger
factory Factory[T]
chain []KvStore[T]
settings *Settings
missingCache KvStore[T]
}
func NewChainKvStore[T any](ctx context.Context, config cfg.Config, logger log.Logger, missingCacheEnabled bool, settings *Settings) (ChainKvStore[T], error) {
if reflect.ValueOf(new(T)).Elem().Kind() == reflect.Pointer {
return nil, fmt.Errorf("the generic type T should not be a pointer type but is of type %T", *new(T))
}
settings.PadFromConfig(config)
factory := buildFactory[T](ctx, config, logger)
var err error
var missingCache KvStore[T]
if missingCacheEnabled {
missingCacheSettings := *settings
missingCacheSettings.Name = fmt.Sprintf("%s-missingCache", settings.Name)
if missingCache, err = NewInMemoryKvStore[T](ctx, config, logger, &missingCacheSettings); err != nil {
return nil, fmt.Errorf("can not create missing cache: %w", err)
}
} else {
missingCache = NewEmptyKvStore[T]()
}
return NewChainKvStoreWithInterfaces[T](logger, factory, missingCache, settings), nil
}
func NewChainKvStoreWithInterfaces[T any](logger log.Logger, factory Factory[T], missingCache KvStore[T], settings *Settings) ChainKvStore[T] {
return &chainKvStore[T]{
logger: logger,
factory: factory,
chain: make([]KvStore[T], 0),
settings: settings,
missingCache: missingCache,
}
}
func (s *chainKvStore[T]) Add(elementFactory ElementFactory[T]) error {
store, err := s.factory(elementFactory, s.settings)
if err != nil {
return fmt.Errorf("can not create store: %w", err)
}
s.AddStore(store)
return nil
}
func (s *chainKvStore[T]) AddStore(store KvStore[T]) {
s.chain = append(s.chain, store)
}
func (s *chainKvStore[T]) Contains(ctx context.Context, key any) (bool, error) {
return s.Get(ctx, key, new(T))
}
func (s *chainKvStore[T]) Get(ctx context.Context, key any, value *T) (bool, error) {
// check if we can short circuit the whole deal
exists, err := s.missingCache.Contains(ctx, key)
if err != nil {
s.logger.WithContext(ctx).Warn("failed to read from missing value cache: %s", err.Error())
}
if exists {
return false, nil
}
lastElementIndex := len(s.chain) - 1
foundInIndex := lastElementIndex + 1
for i, element := range s.chain {
var err error
exists, err = element.Get(ctx, key, value)
if err != nil {
// return error only if last element fails
if i == lastElementIndex {
return false, fmt.Errorf("could not get %s from kvstore %T: %w", key, element, err)
}
s.logger.WithContext(ctx).Warn("could not get %s from kvstore %T: %s", key, element, err.Error())
}
if exists {
foundInIndex = i
break
}
}
// Cache empty value if no result was found
if !exists {
if err := s.missingCache.Put(ctx, key, *new(T)); err != nil {
s.logger.WithContext(ctx).Warn("failed to write to missing value cache: %s", err.Error())
}
return false, nil
}
// propagate to the lower cache levels
for i := foundInIndex - 1; i >= 0; i-- {
err := s.chain[i].Put(ctx, key, *value)
if err != nil {
s.logger.WithContext(ctx).Warn("could not put %s to kvstore %T: %s", key, s.chain[i], err.Error())
}
}
return true, nil
}
func (s *chainKvStore[T]) GetBatch(ctx context.Context, keys any, values any) ([]interface{}, error) {
todo, err := refl.InterfaceToInterfaceSlice(keys)
var cachedMissing []interface{}
if err != nil {
return nil, fmt.Errorf("can not morph keys to slice of interfaces: %w", err)
}
cachedMissingMap := make(map[string]interface{})
todo, err = s.missingCache.GetBatch(ctx, todo, cachedMissingMap)
if err != nil {
s.logger.WithContext(ctx).Warn("failed to read from missing value cache: %s", err.Error())
}
for k := range cachedMissingMap {
cachedMissing = append(cachedMissing, k)
}
if len(todo) == 0 {
return cachedMissing, nil
}
lastElementIndex := len(s.chain) - 1
refill := make(map[int][]interface{})
foundInIndex := lastElementIndex + 1
for i, element := range s.chain {
var err error
refill[i], err = element.GetBatch(ctx, todo, values)
if err != nil {
// return error only if last element fails
if i == lastElementIndex {
return nil, fmt.Errorf("could not get batch from kvstore %T: %w", element, err)
}
s.logger.WithContext(ctx).Warn("could not get batch from kvstore %T: %s", element, err.Error())
refill[i] = todo
}
todo = refill[i]
if len(todo) == 0 {
foundInIndex = i
break
}
}
mii, err := refl.InterfaceToMapInterfaceInterface(values)
if err != nil {
return nil, fmt.Errorf("can not cast result values from %T to map[interface{}]interface{}: %w", values, err)
}
// propagate to the lower cache levels
for i := foundInIndex - 1; i >= 0; i-- {
if len(refill[i]) == 0 {
continue
}
missingInElement := make(map[interface{}]T)
for _, key := range refill[i] {
if val, ok := mii[key]; ok {
missingInElement[key] = val.(T)
}
}
if len(missingInElement) == 0 {
continue
}
err = s.chain[i].PutBatch(ctx, missingInElement)
if err != nil {
s.logger.WithContext(ctx).Warn("could not put batch to kvstore %T: %s", s.chain[i], err.Error())
}
}
// store missing keys
if len(todo) > 0 {
missingValues := make(map[interface{}]interface{}, len(todo))
for _, key := range todo {
missingValues[key] = *new(T)
}
err = s.missingCache.PutBatch(ctx, missingValues)
if err != nil {
s.logger.WithContext(ctx).Warn("could not put batch to empty value cache: %w", err.Error())
}
}
missing := make([]interface{}, 0, len(todo)+len(cachedMissing))
missing = append(missing, todo...)
missing = append(missing, cachedMissing...)
return missing, nil
}
func (s *chainKvStore[T]) Put(ctx context.Context, key any, value T) error {
lastElementIndex := len(s.chain) - 1
for i := 0; i <= lastElementIndex; i++ {
err := s.chain[i].Put(ctx, key, value)
if err != nil {
// return error only if last element fails
if i == lastElementIndex {
return fmt.Errorf("could not put %s to kvstore %T: %w", key, s.chain[i], err)
}
s.logger.WithContext(ctx).Warn("could not put %s to kvstore %T: %s", key, s.chain[i], err.Error())
}
}
// remove the value from the missing value cache only after we persisted it
// otherwise, we might remove it, some other thread adds it again and then we insert
// it into the backing stores
if err := s.missingCache.Delete(ctx, key); err != nil {
s.logger.WithContext(ctx).Warn("could not erase cached empty value for key %s: %s", key, err.Error())
}
return nil
}
func (s *chainKvStore[T]) PutBatch(ctx context.Context, values any) error {
mii, err := refl.InterfaceToMapInterfaceInterface(values)
if err != nil {
return fmt.Errorf("can not cast values from %T to map[interface{}]interface{}: %w", values, err)
}
lastElementIndex := len(s.chain) - 1
for i := 0; i <= lastElementIndex; i++ {
err := s.chain[i].PutBatch(ctx, mii)
if err != nil {
// return error only if last element fails
if i == lastElementIndex {
return fmt.Errorf("could not put batch to kvstore %T: %w", s.chain[i], err)
}
s.logger.WithContext(ctx).Warn("could not put batch to kvstore %T: %s", s.chain[i], err.Error())
}
}
for key := range mii {
if err := s.missingCache.Delete(ctx, key); err != nil {
s.logger.WithContext(ctx).Warn("could not erase cached empty value for key %T %v: %s", key, key, err.Error())
}
}
return nil
}
func (s *chainKvStore[T]) Delete(ctx context.Context, key any) error {
for _, store := range s.chain {
err := store.Delete(ctx, key)
if err != nil {
// even if we do not fail at the last index, we can't leave something
// in a cache but not in the backend store
return fmt.Errorf("could not delete %s from kvstore %T: %w", key, store, err)
}
}
return nil
}
func (s *chainKvStore[T]) DeleteBatch(ctx context.Context, keys any) error {
for _, store := range s.chain {
err := store.DeleteBatch(ctx, keys)
if err != nil {
// even if we do not fail at the last index, we can't leave something
// in a cache but not in the backend store
return fmt.Errorf("could not batch delete from kvstore %T: %w", store, err)
}
}
return nil
}