gotosocial/vendor/codeberg.org/gruf/go-cache/v3/result/cache.go

359 lines
8.5 KiB
Go

package result
import (
"context"
"reflect"
"time"
"codeberg.org/gruf/go-cache/v3/ttl"
"codeberg.org/gruf/go-errors/v2"
)
// 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
// TODO: support toggling case sensitive lookups.
// CaseSensitive 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[Value any] struct {
cache ttl.Cache[int64, result[Value]] // underlying result cache
lookups structKeys // pre-determined struct lookups
ignore func(error) bool // determines cacheable errors
copy func(Value) Value // 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[Value any](lookups []Lookup, copy func(Value) Value, cap int) *Cache[Value] {
var z Value
// 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[Value]{copy: copy}
c.lookups = make([]structKey, len(lookups))
for i, lookup := range lookups {
// Generate keyed field info for lookup
c.lookups[i] = genStructKey(lookup, t)
}
// Create and initialize underlying cache
c.cache.Init(0, cap, 0)
c.SetEvictionCallback(nil)
c.SetInvalidateCallback(nil)
c.IgnoreErrors(nil)
return c
}
// Start will start the cache background eviction routine with given sweep frequency. If already
// running or a freq <= 0 provided, this is a no-op. This will block until eviction routine started.
func (c *Cache[Value]) Start(freq time.Duration) bool {
return c.cache.Start(freq)
}
// Stop will stop cache background eviction routine. If not running this
// is a no-op. This will block until the eviction routine has stopped.
func (c *Cache[Value]) Stop() bool {
return c.cache.Stop()
}
// SetTTL sets the cache item TTL. Update can be specified to force updates of existing items
// in the cache, this will simply add the change in TTL to their current expiry time.
func (c *Cache[Value]) SetTTL(ttl time.Duration, update bool) {
c.cache.SetTTL(ttl, update)
}
// SetEvictionCallback sets the eviction callback to the provided hook.
func (c *Cache[Value]) SetEvictionCallback(hook func(Value)) {
if hook == nil {
// Ensure non-nil hook.
hook = func(Value) {}
}
c.cache.SetEvictionCallback(func(item *ttl.Entry[int64, result[Value]]) {
for _, key := range item.Value.Keys {
// Delete key->pkey lookup
pkeys := key.info.pkeys
delete(pkeys, key.key)
}
if item.Value.Error != nil {
// Skip error hooks
return
}
// Call user hook.
hook(item.Value.Value)
})
}
// SetInvalidateCallback sets the invalidate callback to the provided hook.
func (c *Cache[Value]) SetInvalidateCallback(hook func(Value)) {
if hook == nil {
// Ensure non-nil hook.
hook = func(Value) {}
}
c.cache.SetInvalidateCallback(func(item *ttl.Entry[int64, result[Value]]) {
for _, key := range item.Value.Keys {
// Delete key->pkey lookup
pkeys := key.info.pkeys
delete(pkeys, key.key)
}
if item.Value.Error != nil {
// Skip error hooks
return
}
// Call user hook.
hook(item.Value.Value)
})
}
// IgnoreErrors allows setting a function hook to determine which error types should / not be cached.
func (c *Cache[Value]) IgnoreErrors(ignore func(error) bool) {
if ignore == nil {
ignore = func(err error) bool {
return errors.Is(
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[Value]) Load(lookup string, load func() (Value, error), keyParts ...any) (Value, error) {
var (
zero Value
res result[Value]
)
// Get lookup key info by name.
keyInfo := c.lookups.get(lookup)
// Generate cache key string.
ckey := genKey(keyParts...)
// Acquire cache lock
c.cache.Lock()
// Look for primary cache key
pkey, ok := keyInfo.pkeys[ckey]
if ok {
// Fetch the result for primary key
entry, _ := c.cache.Cache.Get(pkey)
res = entry.Value
}
// Done with lock
c.cache.Unlock()
if !ok {
// Generate fresh result.
value, err := load()
if err != nil {
if c.ignore(err) {
// don't cache this error type
return zero, err
}
// 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 {
// Store value result.
res.Value = value
// This was a successful load, generate keys.
res.Keys = c.lookups.generate(res.Value)
}
// Acquire cache lock.
c.cache.Lock()
defer c.cache.Unlock()
// Cache result
c.store(res)
}
// Catch and return error
if res.Error != nil {
return zero, res.Error
}
// Return a copy of value from cache
return c.copy(res.Value), nil
}
// Store will call the given store function, and on success store the value in the cache as a positive result.
func (c *Cache[Value]) Store(value Value, store func() error) error {
// Attempt to store this value.
if err := store(); err != nil {
return err
}
// Prepare cached result.
result := result[Value]{
Keys: c.lookups.generate(value),
Value: c.copy(value),
Error: nil,
}
// Acquire cache lock.
c.cache.Lock()
defer c.cache.Unlock()
// Cache result
c.store(result)
return nil
}
// Has checks the cache for a positive result under the given lookup and key parts.
func (c *Cache[Value]) Has(lookup string, keyParts ...any) bool {
var res result[Value]
// Get lookup key type by name.
keyType := c.lookups.get(lookup)
// Generate cache key string.
ckey := genKey(keyParts...)
// Acquire cache lock
c.cache.Lock()
// Look for primary key for cache key
pkey, ok := keyType.pkeys[ckey]
if ok {
// Fetch the result for primary key
entry, _ := c.cache.Cache.Get(pkey)
res = entry.Value
}
// Done with lock
c.cache.Unlock()
// Check for non-error result.
return ok && (res.Error == nil)
}
// Invalidate will invalidate any result from the cache found under given lookup and key parts.
func (c *Cache[Value]) Invalidate(lookup string, keyParts ...any) {
// Get lookup key type by name.
keyType := c.lookups.get(lookup)
// Generate cache key string.
ckey := genKey(keyParts...)
// Look for primary key for cache key
c.cache.Lock()
pkey, ok := keyType.pkeys[ckey]
c.cache.Unlock()
if !ok {
return
}
// Invalid by primary key
c.cache.Invalidate(pkey)
}
// Clear empties the cache, calling the invalidate callback.
func (c *Cache[Value]) Clear() {
c.cache.Clear()
}
// store will cache this result under all of its required cache keys.
func (c *Cache[Value]) store(res result[Value]) {
for _, key := range res.Keys {
pkeys := key.info.pkeys
// Look for cache primary key
pkey, ok := pkeys[key.key]
if ok {
// Get the overlapping result with this key.
entry, _ := c.cache.Cache.Get(pkey)
// From conflicting entry, drop this key, this
// will prevent eviction cleanup key confusion.
entry.Value.Keys.drop(key.info.name)
if len(entry.Value.Keys) == 0 {
// We just over-wrote the only lookup key for
// this value, so we drop its primary key too.
c.cache.Cache.Delete(pkey)
}
}
}
// Get primary key
pkey := c.next
c.next++
if pkey > c.next {
panic("cache primary key overflow")
}
// Store all primary key lookups
for _, key := range res.Keys {
pkeys := key.info.pkeys
pkeys[key.key] = pkey
}
// Store main entry under primary key, using evict hook if needed
c.cache.Cache.SetWithHook(pkey, &ttl.Entry[int64, result[Value]]{
Expiry: time.Now().Add(c.cache.TTL),
Key: pkey,
Value: res,
}, func(_ int64, item *ttl.Entry[int64, result[Value]]) {
c.cache.Evict(item)
})
}
type result[Value any] struct {
// keys accessible under
Keys cacheKeys
// cached value
Value Value
// cached error
Error error
}