87 lines
2.4 KiB
Go
87 lines
2.4 KiB
Go
// Copyright 2025 The NATS Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// ats controls the go routines for the access time service.
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// This allows more efficient unixnano operations for cache access times.
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// We will have one per binary (usually per server).
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package ats
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import (
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"sync/atomic"
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"time"
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)
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// Update every 100ms for gathering access time in unix nano.
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const TickInterval = 100 * time.Millisecond
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var (
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// Our unix nano time.
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utime atomic.Int64
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// How may registered users do we have, controls lifetime of Go routine.
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refs atomic.Int64
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// To signal the shutdown of the Go routine.
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done chan struct{}
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)
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func init() {
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// Initialize our done chan.
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done = make(chan struct{}, 1)
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}
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// Register usage. This will happen on filestore creation.
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func Register() {
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if v := refs.Add(1); v == 1 {
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// This is the first to register (could also go up and down),
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// so spin up Go routine and grab initial time.
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utime.Store(time.Now().UnixNano())
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go func() {
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ticker := time.NewTicker(TickInterval)
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defer ticker.Stop()
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for {
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select {
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case <-ticker.C:
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utime.Store(time.Now().UnixNano())
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case <-done:
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return
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}
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}
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}()
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}
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}
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// Unregister usage. We will shutdown the go routine if no more registered users.
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func Unregister() {
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if v := refs.Add(-1); v == 0 {
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done <- struct{}{}
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} else if v < 0 {
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refs.Store(0)
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panic("unbalanced unregister for access time state")
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}
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}
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// Will load the access time from an atomic.
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// If no one has registered this will return 0 or stale data.
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// It is the responsibility of the user to properly register and unregister.
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func AccessTime() int64 {
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// Return last updated time.
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v := utime.Load()
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if v == 0 {
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// Always register a time, the worst case is a stale time.
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// On startup, we can register in parallel and could previously panic.
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v = time.Now().UnixNano()
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utime.Store(v)
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}
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return v
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}
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