mirror of https://github.com/status-im/consul.git
124 lines
3.8 KiB
Go
124 lines
3.8 KiB
Go
package cache
|
|
|
|
import (
|
|
"container/heap"
|
|
"time"
|
|
)
|
|
|
|
// cacheEntryExpiry contains the expiration time for a cache entry.
|
|
type cacheEntryExpiry struct {
|
|
Key string // Key in the cache map
|
|
Expires time.Time // Time when entry expires (monotonic clock)
|
|
HeapIndex int // Index in the heap
|
|
}
|
|
|
|
// TODO: use or remove
|
|
func newCacheEntry(key string, expiry time.Duration) *cacheEntryExpiry {
|
|
return &cacheEntryExpiry{Key: key, Expires: time.Now().Add(expiry)}
|
|
}
|
|
|
|
// expiryHeap is a container/heap.Interface implementation that expires entries
|
|
// in the cache when their expiration time is reached.
|
|
//
|
|
// All operations on the heap and read/write of the heap contents require
|
|
// the proper entriesLock to be held on Cache.
|
|
type expiryHeap struct {
|
|
Entries []*cacheEntryExpiry
|
|
|
|
// NotifyCh is sent a value whenever the 0 index value of the heap
|
|
// changes. This can be used to detect when the earliest value
|
|
// changes.
|
|
//
|
|
// There is a single edge case where the heap will not automatically
|
|
// send a notification: if heap.Fix is called manually and the index
|
|
// changed is 0 and the change doesn't result in any moves (stays at index
|
|
// 0), then we won't detect the change. To work around this, please
|
|
// always call the expiryHeap.Fix method instead.
|
|
NotifyCh chan struct{}
|
|
}
|
|
|
|
func (h *expiryHeap) Add(key string, expiry time.Duration) *cacheEntryExpiry {
|
|
entry := &cacheEntryExpiry{Key: key, Expires: time.Now().Add(expiry)}
|
|
heap.Push(h, entry)
|
|
return entry
|
|
}
|
|
|
|
// Update the entry that is currently at idx with the new expiry time. The heap
|
|
// will be rebalanced after the entry is updated.
|
|
//
|
|
// Must be synchronized by the caller.
|
|
func (h *expiryHeap) Update(idx int, expiry time.Duration) {
|
|
entry := h.Entries[idx]
|
|
entry.Expires = time.Now().Add(expiry)
|
|
heap.Fix(h, idx)
|
|
|
|
// If the previous index and current index are both zero then Fix did not
|
|
// swap the entry, and notify must be called here.
|
|
if idx == 0 && entry.HeapIndex == 0 {
|
|
h.notify()
|
|
}
|
|
}
|
|
|
|
func (h *expiryHeap) Len() int { return len(h.Entries) }
|
|
|
|
func (h *expiryHeap) Swap(i, j int) {
|
|
h.Entries[i], h.Entries[j] = h.Entries[j], h.Entries[i]
|
|
h.Entries[i].HeapIndex = i
|
|
h.Entries[j].HeapIndex = j
|
|
|
|
// If we're moving the 0 index, update the channel since we need
|
|
// to re-update the timer we're waiting on for the soonest expiring
|
|
// value.
|
|
if i == 0 || j == 0 {
|
|
h.notify()
|
|
}
|
|
}
|
|
|
|
func (h *expiryHeap) Less(i, j int) bool {
|
|
// The usage of Before here is important (despite being obvious):
|
|
// this function uses the monotonic time that should be available
|
|
// on the time.Time value so the heap is immune to wall clock changes.
|
|
return h.Entries[i].Expires.Before(h.Entries[j].Expires)
|
|
}
|
|
|
|
// heap.Interface, this isn't expected to be called directly.
|
|
func (h *expiryHeap) Push(x interface{}) {
|
|
entry := x.(*cacheEntryExpiry)
|
|
|
|
// Set the initial heap index to the last index. If the entry is swapped it
|
|
// will have the correct set, and if it remains at the end the last index will
|
|
// be correct.
|
|
entry.HeapIndex = len(h.Entries)
|
|
|
|
// For the first entry, we need to trigger a channel send because
|
|
// Swap won't be called; nothing to swap! We can call it right away
|
|
// because all heap operations are within a lock.
|
|
if len(h.Entries) == 0 {
|
|
h.notify()
|
|
}
|
|
|
|
h.Entries = append(h.Entries, entry)
|
|
}
|
|
|
|
// heap.Interface, this isn't expected to be called directly.
|
|
func (h *expiryHeap) Pop() interface{} {
|
|
n := len(h.Entries)
|
|
entries := h.Entries
|
|
last := entries[n-1]
|
|
h.Entries = entries[0 : n-1]
|
|
return last
|
|
}
|
|
|
|
func (h *expiryHeap) notify() {
|
|
select {
|
|
case h.NotifyCh <- struct{}{}:
|
|
// Good
|
|
|
|
default:
|
|
// If the send would've blocked, we just ignore it. The reason this
|
|
// is safe is because NotifyCh should always be a buffered channel.
|
|
// If this blocks, it means that there is a pending message anyways
|
|
// so the receiver will restart regardless.
|
|
}
|
|
}
|