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Fix #72: Connected placeholder shouldn't resolve to true when when host is unreachable

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This commit is contained in:
TwinProduction
2021-01-12 21:08:18 -05:00
parent a515335c15
commit aec867ae69
9 changed files with 279 additions and 121 deletions
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175
vendor/github.com/TwinProduction/gocache/gocache.go generated vendored
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@ -2,13 +2,16 @@ package gocache
import (
"errors"
"reflect"
"sync"
"time"
)
const (
var (
Debug = false
)
const (
// NoMaxSize means that the cache has no maximum number of entries in the cache
// Setting Cache.maxSize to this value also means there will be no eviction
NoMaxSize = 0
@ -23,15 +26,14 @@ const (
NoExpiration = -1
Kilobyte = 1024
Megabyte = 1024 * 1024
Gigabyte = 1024 * 1024 * 1024
Megabyte = 1024 * Kilobyte
Gigabyte = 1024 * Megabyte
)
var (
ErrKeyDoesNotExist = errors.New("key does not exist")
ErrKeyHasNoExpiration = errors.New("key has no expiration")
ErrJanitorAlreadyRunning = errors.New("janitor is already running")
ErrAutoSaveAlreadyRunning = errors.New("autosave is already running")
ErrKeyDoesNotExist = errors.New("key does not exist")
ErrKeyHasNoExpiration = errors.New("key has no expiration")
ErrJanitorAlreadyRunning = errors.New("janitor is already running")
)
// Cache is the core struct of gocache which contains the data as well as all relevant configuration fields
@ -68,6 +70,15 @@ type Cache struct {
// memoryUsage is the approximate memory usage of the cache (dataset only) in bytes
memoryUsage int
// forceNilInterfaceOnNilPointer determines whether all Set-like functions should set a value as nil if the
// interface passed has a nil value but not a nil type.
//
// By default, interfaces are only nil when both their type and value is nil.
// This means that when you pass a pointer to a nil value, the type of the interface
// will still show as nil, which means that if you don't cast the interface after
// retrieving it, a nil check will return that the value is not false.
forceNilInterfaceOnNilPointer bool
}
// MaxSize returns the maximum amount of keys that can be present in the cache before
@ -87,8 +98,16 @@ func (cache *Cache) EvictionPolicy() EvictionPolicy {
}
// Stats returns statistics from the cache
func (cache *Cache) Stats() *Statistics {
return cache.stats
func (cache *Cache) Stats() Statistics {
cache.mutex.RLock()
stats := Statistics{
EvictedKeys: cache.stats.EvictedKeys,
ExpiredKeys: cache.stats.ExpiredKeys,
Hits: cache.stats.Hits,
Misses: cache.stats.Misses,
}
cache.mutex.RUnlock()
return stats
}
// MemoryUsage returns the current memory usage of the cache's dataset in bytes
@ -103,6 +122,9 @@ func (cache *Cache) WithMaxSize(maxSize int) *Cache {
if maxSize < 0 {
maxSize = NoMaxSize
}
if maxSize != NoMaxSize && cache.Count() == 0 {
cache.entries = make(map[string]*Entry, maxSize)
}
cache.maxSize = maxSize
return cache
}
@ -127,20 +149,62 @@ func (cache *Cache) WithEvictionPolicy(policy EvictionPolicy) *Cache {
return cache
}
// WithForceNilInterfaceOnNilPointer sets whether all Set-like functions should set a value as nil if the
// interface passed has a nil value but not a nil type.
//
// In Go, an interface is only nil if both its type and value are nil, which means that a nil pointer
// (e.g. (*Struct)(nil)) will retain its attribution to the type, and the unmodified value returned from
// Cache.Get, for instance, would return false when compared with nil if this option is set to false.
//
// We can bypass this by detecting if the interface's value is nil and setting it to nil rather than
// a nil pointer, which will make the value returned from Cache.Get return true when compared with nil.
// This is exactly what passing true to WithForceNilInterfaceOnNilPointer does, and it's also the default behavior.
//
// Alternatively, you may pass false to WithForceNilInterfaceOnNilPointer, which will mean that you'll have
// to cast the value returned from Cache.Get to its original type to check for whether the pointer returned
// is nil or not.
//
// If set to true:
// cache := gocache.NewCache().WithForceNilInterfaceOnNilPointer(true)
// cache.Set("key", (*Struct)(nil))
// value, _ := cache.Get("key")
// // the following returns true, because the interface{} was forcefully set to nil
// if value == nil {}
// // the following will panic, because the value has been casted to its type
// if value.(*Struct) == nil {}
//
// If set to false:
// cache := gocache.NewCache().WithForceNilInterfaceOnNilPointer(false)
// cache.Set("key", (*Struct)(nil))
// value, _ := cache.Get("key")
// // the following returns false, because the interface{} returned has a non-nil type (*Struct)
// if value == nil {}
// // the following returns true, because the value has been casted to its type
// if value.(*Struct) == nil {}
//
// In other words, if set to true, you do not need to cast the value returned from the cache to
// to check if the value is nil.
//
// Defaults to true
func (cache *Cache) WithForceNilInterfaceOnNilPointer(forceNilInterfaceOnNilPointer bool) *Cache {
cache.forceNilInterfaceOnNilPointer = forceNilInterfaceOnNilPointer
return cache
}
// NewCache creates a new Cache
//
// Should be used in conjunction with Cache.WithMaxSize, Cache.WithMaxMemoryUsage and/or Cache.WithEvictionPolicy
//
// gocache.NewCache().WithMaxSize(10000).WithEvictionPolicy(gocache.LeastRecentlyUsed)
//
func NewCache() *Cache {
return &Cache{
maxSize: DefaultMaxSize,
evictionPolicy: FirstInFirstOut,
stats: &Statistics{},
entries: make(map[string]*Entry),
mutex: sync.RWMutex{},
stopJanitor: nil,
maxSize: DefaultMaxSize,
evictionPolicy: FirstInFirstOut,
stats: &Statistics{},
entries: make(map[string]*Entry),
mutex: sync.RWMutex{},
stopJanitor: nil,
forceNilInterfaceOnNilPointer: true,
}
}
@ -150,13 +214,22 @@ func (cache *Cache) Set(key string, value interface{}) {
}
// SetWithTTL creates or updates a key with a given value and sets an expiration time (-1 is NoExpiration)
//
// The TTL provided must be greater than 0, or NoExpiration (-1). If a negative value that isn't -1 (NoExpiration) is
// provided, the entry will not be created if the key doesn't exist
func (cache *Cache) SetWithTTL(key string, value interface{}, ttl time.Duration) {
// An interface is only nil if both its value and its type are nil, however, passing a pointer
if cache.forceNilInterfaceOnNilPointer {
if value != nil && (reflect.ValueOf(value).Kind() == reflect.Ptr && reflect.ValueOf(value).IsNil()) {
value = nil
}
}
cache.mutex.Lock()
entry, ok := cache.get(key)
if !ok {
// A negative TTL that isn't -1 (NoExpiration) is an entry that will expire instantly,
// A negative TTL that isn't -1 (NoExpiration) or 0 is an entry that will expire instantly,
// so might as well just not create it in the first place
if ttl != NoExpiration && ttl < 0 {
if ttl != NoExpiration && ttl < 1 {
cache.mutex.Unlock()
return
}
@ -178,6 +251,13 @@ func (cache *Cache) SetWithTTL(key string, value interface{}, ttl time.Duration)
cache.memoryUsage += entry.SizeInBytes()
}
} else {
// A negative TTL that isn't -1 (NoExpiration) or 0 is an entry that will expire instantly,
// so might as well just delete it immediately instead of updating it
if ttl != NoExpiration && ttl < 1 {
cache.delete(key)
cache.mutex.Unlock()
return
}
if cache.maxMemoryUsage != NoMaxMemoryUsage {
// Substract the old entry from the cache's memoryUsage
cache.memoryUsage -= entry.SizeInBytes()
@ -234,12 +314,13 @@ func (cache *Cache) Get(key string) (interface{}, bool) {
cache.stats.Misses++
return nil, false
}
cache.stats.Hits++
if entry.Expired() {
cache.stats.ExpiredKeys++
cache.delete(key)
cache.mutex.Unlock()
return nil, false
}
cache.stats.Hits++
if cache.evictionPolicy == LeastRecentlyUsed {
entry.Accessed()
if cache.head == entry {
@ -253,12 +334,11 @@ func (cache *Cache) Get(key string) (interface{}, bool) {
return entry.Value, true
}
// GetAll retrieves multiple entries using the keys passed as parameter
// All keys are returned in the map, regardless of whether they exist or not,
// however, entries that do not exist in the cache will return nil, meaning that
// there is no way of determining whether a key genuinely has the value nil, or
// whether it doesn't exist in the cache using only this function
func (cache *Cache) GetAll(keys []string) map[string]interface{} {
// GetByKeys retrieves multiple entries using the keys passed as parameter
// All keys are returned in the map, regardless of whether they exist or not, however, entries that do not exist in the
// cache will return nil, meaning that there is no way of determining whether a key genuinely has the value nil, or
// whether it doesn't exist in the cache using only this function.
func (cache *Cache) GetByKeys(keys []string) map[string]interface{} {
entries := make(map[string]interface{})
for _, key := range keys {
entries[key], _ = cache.Get(key)
@ -266,18 +346,51 @@ func (cache *Cache) GetAll(keys []string) map[string]interface{} {
return entries
}
// GetAll retrieves all cache entries
//
// If the eviction policy is LeastRecentlyUsed, note that unlike Get and GetByKeys, this does not update the last access
// timestamp. The reason for this is that since all cache entries will be accessed, updating the last access timestamp
// would provide very little benefit while harming the ability to accurately determine the next key that will be evicted
//
// You should probably avoid using this if you have a lot of entries.
//
// GetKeysByPattern is a good alternative if you want to retrieve entries that you do not have the key for, as it only
// retrieves the keys and does not trigger active eviction and has a parameter for setting a limit to the number of keys
// you wish to retrieve.
func (cache *Cache) GetAll() map[string]interface{} {
entries := make(map[string]interface{})
cache.mutex.Lock()
for key, entry := range cache.entries {
if entry.Expired() {
cache.delete(key)
continue
}
entries[key] = entry.Value
}
cache.stats.Hits += uint64(len(entries))
cache.mutex.Unlock()
return entries
}
// GetKeysByPattern retrieves a slice of keys that match a given pattern
// If the limit is set to 0, the entire cache will be searched for matching keys.
// If the limit is above 0, the search will stop once the specified number of matching keys have been found.
//
// e.g. cache.GetKeysByPattern("*some*", 0) will return all keys containing "some" in them
// e.g. cache.GetKeysByPattern("*some*", 5) will return 5 keys (or less) containing "some" in them
// e.g.
// cache.GetKeysByPattern("*some*", 0) will return all keys containing "some" in them
// cache.GetKeysByPattern("*some*", 5) will return 5 keys (or less) containing "some" in them
//
// Note that GetKeysByPattern does not trigger evictions, nor does it count as accessing the entry.
// Note that GetKeysByPattern does not trigger active evictions, nor does it count as accessing the entry, the latter
// only applying if the cache uses the LeastRecentlyUsed eviction policy.
// The reason for that behavior is that these two (active eviction and access) only applies when you access the value
// of the cache entry, and this function only returns the keys.
func (cache *Cache) GetKeysByPattern(pattern string, limit int) []string {
var matchingKeys []string
cache.mutex.RLock()
for key := range cache.entries {
cache.mutex.Lock()
for key, value := range cache.entries {
if value.Expired() {
continue
}
if MatchPattern(pattern, key) {
matchingKeys = append(matchingKeys, key)
if limit > 0 && len(matchingKeys) >= limit {
@ -285,7 +398,7 @@ func (cache *Cache) GetKeysByPattern(pattern string, limit int) []string {
}
}
}
cache.mutex.RUnlock()
cache.mutex.Unlock()
return matchingKeys
}