package zerolog import ( "math/rand" "sync/atomic" "time" ) var ( // Often samples log every ~ 10 events. Often = RandomSampler(10) // Sometimes samples log every ~ 100 events. Sometimes = RandomSampler(100) // Rarely samples log every ~ 1000 events. Rarely = RandomSampler(1000) ) // 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(lvl Level) bool } // RandomSampler use a PRNG to randomly sample an event out of N events, // regardless of their level. type RandomSampler uint32 // Sample implements the Sampler interface. func (s RandomSampler) Sample(lvl Level) bool { if s <= 0 { return false } if rand.Intn(int(s)) != 0 { return false } return true } // BasicSampler is a sampler that will send every Nth events, regardless of // there level. type BasicSampler struct { N uint32 counter uint32 } // Sample implements the Sampler interface. func (s *BasicSampler) Sample(lvl Level) bool { n := s.N if n == 1 { return true } c := atomic.AddUint32(&s.counter, 1) return c%n == 1 } // BurstSampler lets Burst events pass per Period then pass the decision to // NextSampler. If Sampler is not set, all subsequent events are rejected. type BurstSampler struct { // Burst is the maximum number of event per period allowed before calling // NextSampler. Burst uint32 // Period defines the burst period. If 0, NextSampler is always called. Period time.Duration // NextSampler is the sampler used after the burst is reached. If nil, // events are always rejected after the burst. NextSampler Sampler counter uint32 resetAt int64 } // Sample implements the Sampler interface. func (s *BurstSampler) Sample(lvl Level) bool { if s.Burst > 0 && s.Period > 0 { if s.inc() <= s.Burst { return true } } if s.NextSampler == nil { return false } return s.NextSampler.Sample(lvl) } func (s *BurstSampler) inc() uint32 { now := time.Now().UnixNano() resetAt := atomic.LoadInt64(&s.resetAt) var c uint32 if now > resetAt { c = 1 atomic.StoreUint32(&s.counter, c) newResetAt := now + s.Period.Nanoseconds() reset := atomic.CompareAndSwapInt64(&s.resetAt, resetAt, newResetAt) if !reset { // Lost the race with another goroutine trying to reset. c = atomic.AddUint32(&s.counter, 1) } } else { c = atomic.AddUint32(&s.counter, 1) } return c } // LevelSampler applies a different sampler for each level. type LevelSampler struct { DebugSampler, InfoSampler, WarnSampler, ErrorSampler Sampler } func (s LevelSampler) Sample(lvl Level) bool { switch lvl { case DebugLevel: if s.DebugSampler != nil { return s.DebugSampler.Sample(lvl) } case InfoLevel: if s.InfoSampler != nil { return s.InfoSampler.Sample(lvl) } case WarnLevel: if s.WarnSampler != nil { return s.WarnSampler.Sample(lvl) } case ErrorLevel: if s.ErrorSampler != nil { return s.ErrorSampler.Sample(lvl) } } return true }