mirror of
https://github.com/VictoriaMetrics/VictoriaMetrics.git
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90 lines
2.6 KiB
Go
90 lines
2.6 KiB
Go
package bytesutil
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import (
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"strings"
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"sync"
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"sync/atomic"
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"github.com/VictoriaMetrics/VictoriaMetrics/lib/fasttime"
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)
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// FastStringMatcher implements fast matcher for strings.
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//
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// It caches string match results and returns them back on the next calls
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// without calling the matchFunc, which may be expensive.
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type FastStringMatcher struct {
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lastCleanupTime uint64
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m sync.Map
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matchFunc func(s string) bool
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}
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type fsmEntry struct {
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lastAccessTime uint64
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ok bool
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}
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// NewFastStringMatcher creates new matcher, which applies matchFunc to strings passed to Match()
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//
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// matchFunc must return the same result for the same input.
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func NewFastStringMatcher(matchFunc func(s string) bool) *FastStringMatcher {
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return &FastStringMatcher{
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lastCleanupTime: fasttime.UnixTimestamp(),
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matchFunc: matchFunc,
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}
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}
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// Match applies matchFunc to s and returns the result.
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func (fsm *FastStringMatcher) Match(s string) bool {
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ct := fasttime.UnixTimestamp()
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v, ok := fsm.m.Load(s)
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if ok {
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// Fast path - s match result is found in the cache.
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e := v.(*fsmEntry)
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if atomic.LoadUint64(&e.lastAccessTime)+10 < ct {
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// Reduce the frequency of e.lastAccessTime update to once per 10 seconds
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// in order to improve the fast path speed on systems with many CPU cores.
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atomic.StoreUint64(&e.lastAccessTime, ct)
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}
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return e.ok
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}
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// Slow path - run matchFunc for s and store the result in the cache.
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b := fsm.matchFunc(s)
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e := &fsmEntry{
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lastAccessTime: ct,
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ok: b,
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}
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// Make a copy of s in order to limit memory usage to the s length,
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// since the s may point to bigger string.
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// This also protects from the case when s contains unsafe string, which points to a temporary byte slice.
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// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3227
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s = strings.Clone(s)
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fsm.m.Store(s, e)
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if needCleanup(&fsm.lastCleanupTime, ct) {
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// Perform a global cleanup for fsm.m by removing items, which weren't accessed during the last 5 minutes.
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m := &fsm.m
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m.Range(func(k, v interface{}) bool {
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e := v.(*fsmEntry)
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if atomic.LoadUint64(&e.lastAccessTime)+5*60 < ct {
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m.Delete(k)
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}
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return true
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})
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}
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return b
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}
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func needCleanup(lastCleanupTime *uint64, currentTime uint64) bool {
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lct := atomic.LoadUint64(lastCleanupTime)
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if lct+61 >= currentTime {
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return false
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}
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// Atomically compare and swap the current time with the lastCleanupTime
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// in order to guarantee that only a single goroutine out of multiple
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// concurrently executing goroutines gets true from the call.
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return atomic.CompareAndSwapUint64(lastCleanupTime, lct, currentTime)
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}
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