gotosocial/vendor/codeberg.org/gruf/go-cache/v3/result/cache.go
kim 6f4ae8f58d
[bugfix] update cache library with nil ptr fix (#2070)
Signed-off-by: kim <grufwub@gmail.com>
2023-08-06 11:55:04 +02:00

450 lines
10 KiB
Go

package result
import (
"context"
"fmt"
"os"
"reflect"
_ "unsafe"
"codeberg.org/gruf/go-cache/v3/simple"
"codeberg.org/gruf/go-errors/v2"
)
var ErrUnsupportedZero = errors.New("")
// Lookup represents a struct object lookup method in the cache.
type Lookup struct {
// Name is a period ('.') separated string
// of struct fields this Key encompasses.
Name string
// AllowZero indicates whether to accept and cache
// under zero value keys, otherwise ignore them.
AllowZero bool
// Multi allows specifying a key capable of storing
// multiple results. Note this only supports invalidate.
Multi bool
}
// Cache provides a means of caching value structures, along with
// the results of attempting to load them. An example usecase of this
// cache would be in wrapping a database, allowing caching of sql.ErrNoRows.
type Cache[T any] struct {
cache simple.Cache[int64, *result] // underlying result cache
lookups structKeys // pre-determined struct lookups
invalid func(T) // store unwrapped invalidate callback.
ignore func(error) bool // determines cacheable errors
copy func(T) T // copies a Value type
next int64 // update key counter
}
// New returns a new initialized Cache, with given lookups, underlying value copy function and provided capacity.
func New[T any](lookups []Lookup, copy func(T) T, cap int) *Cache[T] {
var z T
// Determine generic type
t := reflect.TypeOf(z)
// Iteratively deref pointer type
for t.Kind() == reflect.Pointer {
t = t.Elem()
}
// Ensure that this is a struct type
if t.Kind() != reflect.Struct {
panic("generic parameter type must be struct (or ptr to)")
}
// Allocate new cache object
c := &Cache[T]{copy: copy}
c.lookups = make([]structKey, len(lookups))
for i, lookup := range lookups {
// Create keyed field info for lookup
c.lookups[i] = newStructKey(lookup, t)
}
// Create and initialize underlying cache
c.cache.Init(0, cap)
c.SetEvictionCallback(nil)
c.SetInvalidateCallback(nil)
c.IgnoreErrors(nil)
return c
}
// SetEvictionCallback sets the eviction callback to the provided hook.
func (c *Cache[T]) SetEvictionCallback(hook func(T)) {
if hook == nil {
// Ensure non-nil hook.
hook = func(T) {}
}
c.cache.SetEvictionCallback(func(pkey int64, res *result) {
c.cache.Lock()
for _, key := range res.Keys {
// Delete key->pkey lookup
pkeys := key.info.pkeys
delete(pkeys, key.key)
}
c.cache.Unlock()
if res.Error != nil {
// Skip value hooks
putResult(res)
return
}
// Free result and call hook.
v := getResultValue[T](res)
putResult(res)
hook(v)
})
}
// SetInvalidateCallback sets the invalidate callback to the provided hook.
func (c *Cache[T]) SetInvalidateCallback(hook func(T)) {
if hook == nil {
// Ensure non-nil hook.
hook = func(T) {}
} // store hook.
c.invalid = hook
c.cache.SetInvalidateCallback(func(pkey int64, res *result) {
c.cache.Lock()
for _, key := range res.Keys {
// Delete key->pkey lookup
pkeys := key.info.pkeys
delete(pkeys, key.key)
}
c.cache.Unlock()
if res.Error != nil {
// Skip value hooks
putResult(res)
return
}
// Free result and call hook.
v := getResultValue[T](res)
putResult(res)
hook(v)
})
}
// IgnoreErrors allows setting a function hook to determine which error types should / not be cached.
func (c *Cache[T]) IgnoreErrors(ignore func(error) bool) {
if ignore == nil {
ignore = func(err error) bool {
return errors.Comparable(
err,
context.Canceled,
context.DeadlineExceeded,
)
}
}
c.cache.Lock()
c.ignore = ignore
c.cache.Unlock()
}
// Load will attempt to load an existing result from the cacche for the given lookup and key parts, else calling the provided load function and caching the result.
func (c *Cache[T]) Load(lookup string, load func() (T, error), keyParts ...any) (T, error) {
var zero T
var res *result
// Get lookup key info by name.
keyInfo := c.lookups.get(lookup)
if !keyInfo.unique {
panic("non-unique lookup does not support load: " + lookup)
}
// Generate cache key string.
ckey := keyInfo.genKey(keyParts)
// Acquire cache lock
c.cache.Lock()
// Look for primary key for cache key (only accept len=1)
if pkeys := keyInfo.pkeys[ckey]; len(pkeys) == 1 {
// Fetch the result for primary key
entry, ok := c.cache.Cache.Get(pkeys[0])
if ok {
// Since the invalidation / eviction hooks acquire a mutex
// lock separately, and only at this point are the pkeys
// updated, there is a chance that a primary key may return
// no matching entry. Hence we have to check for it here.
res = entry.Value.(*result)
}
}
// Done with lock
c.cache.Unlock()
if res == nil {
// Generate fresh result.
value, err := load()
if err != nil {
if c.ignore(err) {
// don't cache this error type
return zero, err
}
// Alloc result.
res = getResult()
// Store error result.
res.Error = err
// This load returned an error, only
// store this item under provided key.
res.Keys = []cacheKey{{
info: keyInfo,
key: ckey,
}}
} else {
// Alloc result.
res = getResult()
// Store value result.
res.Value = value
// This was a successful load, generate keys.
res.Keys = c.lookups.generate(res.Value)
}
var evict func()
// Lock cache.
c.cache.Lock()
defer func() {
// Unlock cache.
c.cache.Unlock()
if evict != nil {
// Call evict.
evict()
}
}()
// Store result in cache.
evict = c.store(res)
}
// Catch and return cached error
if err := res.Error; err != nil {
return zero, err
}
// Copy value from cached result.
v := c.copy(getResultValue[T](res))
return v, nil
}
// Store will call the given store function, and on success store the value in the cache as a positive result.
func (c *Cache[T]) Store(value T, store func() error) error {
// Attempt to store this value.
if err := store(); err != nil {
return err
}
// Prepare cached result.
result := getResult()
result.Keys = c.lookups.generate(value)
result.Value = c.copy(value)
result.Error = nil
var evict func()
// Lock cache.
c.cache.Lock()
defer func() {
// Unlock cache.
c.cache.Unlock()
if evict != nil {
// Call evict.
evict()
}
// Call invalidate.
c.invalid(value)
}()
// Store result in cache.
evict = c.store(result)
return nil
}
// Has checks the cache for a positive result under the given lookup and key parts.
func (c *Cache[T]) Has(lookup string, keyParts ...any) bool {
var res *result
// Get lookup key info by name.
keyInfo := c.lookups.get(lookup)
if !keyInfo.unique {
panic("non-unique lookup does not support has: " + lookup)
}
// Generate cache key string.
ckey := keyInfo.genKey(keyParts)
// Acquire cache lock
c.cache.Lock()
// Look for primary key for cache key (only accept len=1)
if pkeys := keyInfo.pkeys[ckey]; len(pkeys) == 1 {
// Fetch the result for primary key
entry, ok := c.cache.Cache.Get(pkeys[0])
if ok {
// Since the invalidation / eviction hooks acquire a mutex
// lock separately, and only at this point are the pkeys
// updated, there is a chance that a primary key may return
// no matching entry. Hence we have to check for it here.
res = entry.Value.(*result)
}
}
// Check for result AND non-error result.
ok := (res != nil && res.Error == nil)
// Done with lock
c.cache.Unlock()
return ok
}
// Invalidate will invalidate any result from the cache found under given lookup and key parts.
func (c *Cache[T]) Invalidate(lookup string, keyParts ...any) {
// Get lookup key info by name.
keyInfo := c.lookups.get(lookup)
// Generate cache key string.
ckey := keyInfo.genKey(keyParts)
// Look for primary key for cache key
c.cache.Lock()
pkeys := keyInfo.pkeys[ckey]
delete(keyInfo.pkeys, ckey)
c.cache.Unlock()
// Invalidate all primary keys.
c.cache.InvalidateAll(pkeys...)
}
// Clear empties the cache, calling the invalidate callback where necessary.
func (c *Cache[T]) Clear() { c.Trim(100) }
// Trim ensures the cache stays within percentage of total capacity, truncating where necessary.
func (c *Cache[T]) Trim(perc float64) { c.cache.Trim(perc) }
// store will cache this result under all of its required cache keys.
func (c *Cache[T]) store(res *result) (evict func()) {
var toEvict []*result
// Get primary key
res.PKey = c.next
c.next++
if res.PKey > c.next {
panic("cache primary key overflow")
}
for _, key := range res.Keys {
// Look for cache primary keys.
pkeys := key.info.pkeys[key.key]
if key.info.unique && len(pkeys) > 0 {
for _, conflict := range pkeys {
// Get the overlapping result with this key.
entry, ok := c.cache.Cache.Get(conflict)
if !ok {
// Since the invalidation / eviction hooks acquire a mutex
// lock separately, and only at this point are the pkeys
// updated, there is a chance that a primary key may return
// no matching entry. Hence we have to check for it here.
continue
}
// From conflicting entry, drop this key, this
// will prevent eviction cleanup key confusion.
confRes := entry.Value.(*result)
confRes.Keys.drop(key.info.name)
if len(res.Keys) == 0 {
// We just over-wrote the only lookup key for
// this value, so we drop its primary key too.
_ = c.cache.Cache.Delete(conflict)
// Add finished result to evict queue.
toEvict = append(toEvict, confRes)
}
}
// Drop existing.
pkeys = pkeys[:0]
}
// Store primary key lookup.
pkeys = append(pkeys, res.PKey)
key.info.pkeys[key.key] = pkeys
}
// Acquire new cache entry.
entry := simple.GetEntry()
entry.Key = res.PKey
entry.Value = res
evictFn := func(_ int64, entry *simple.Entry) {
// on evict during set, store evicted result.
toEvict = append(toEvict, entry.Value.(*result))
}
// Store main entry under primary key, catch evicted.
c.cache.Cache.SetWithHook(res.PKey, entry, evictFn)
if len(toEvict) == 0 {
// none evicted.
return nil
}
return func() {
for i := range toEvict {
// Rescope result.
res := toEvict[i]
// Call evict hook on each entry.
c.cache.Evict(res.PKey, res)
}
}
}
type result struct {
// Result primary key
PKey int64
// keys accessible under
Keys cacheKeys
// cached value
Value any
// cached error
Error error
}
// getResultValue is a safe way of casting and fetching result value.
func getResultValue[T any](res *result) T {
v, ok := res.Value.(T)
if !ok {
fmt.Fprintf(os.Stderr, "!! BUG: unexpected value type in result: %T\n", res.Value)
}
return v
}