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sampler.go
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sampler.go
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//
// DISCLAIMER
//
// Copyright 2024 ArangoDB GmbH, Cologne, Germany
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// Copyright holder is ArangoDB GmbH, Cologne, Germany
//
package logging
import (
"fmt"
goSync "sync"
"time"
"github.com/arangodb/kube-arangodb/pkg/util/sync"
)
// Sampler defines an interface to a log sampler.
type Sampler interface {
// Sample returns true if the event should be part of the sample, false if
// the event should be dropped.
Sample(level Level, msg string, args ...any) bool
}
func NewLogEventSampler(period time.Duration) Sampler {
return &logEventSampler{
period: period,
}
}
type logEventSampler struct {
// period defines the burst period
period time.Duration
// lruCache is the thread-safe map of message hash -> timestamp when event happened last time
lruCache sync.Map[string, int64]
gcLock goSync.Mutex
gcCycle uint64
}
func (s *logEventSampler) Sample(level Level, format string, args ...any) bool {
if s.period <= 0 {
// sampling disabled
return true
}
s.gc()
hash := s.hash(level, format, args...)
return s.store(hash)
}
func (s *logEventSampler) hash(level Level, format string, args ...any) string {
msg := fmt.Sprintf(format, args...)
return fmt.Sprintf("%s_%s", level.String(), msg)
}
// store returns true if event hash was not stored, or it was stored more than s.period ago
func (s *logEventSampler) store(hash string) bool {
storedAt, _ := s.lruCache.LoadOrStore(hash, 0)
now := time.Now().UnixNano()
if now > storedAt {
newStoredAt := now + s.period.Nanoseconds()
return s.lruCache.CompareAndSwap(hash, storedAt, newStoredAt)
}
return false
}
func (s *logEventSampler) gc() {
s.gcLock.Lock()
defer s.gcLock.Unlock()
s.gcCycle++
if s.gcCycle > 10e5 {
// run cache cleanup every 10e5 cycles
s.gcClean()
s.gcCycle = 0
}
}
func (s *logEventSampler) gcClean() {
now := time.Now().UnixNano()
s.lruCache.Range(func(key string, value int64) bool {
gcPeriod := (time.Minute * 15).Nanoseconds()
if now-value > gcPeriod {
s.lruCache.Delete(key)
}
return true
})
}