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// Copyright (c) 2016-2022 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package zapcore
import (
"time"
"go.uber.org/atomic"
)
const (
_numLevels = _maxLevel - _minLevel + 1
_countersPerLevel = 4096
)
type counter struct {
resetAt atomic.Int64
counter atomic.Uint64
}
type counters [_numLevels][_countersPerLevel]counter
func newCounters() *counters {
return &counters{}
}
func (cs *counters) get(lvl Level, key string) *counter {
i := lvl - _minLevel
j := fnv32a(key) % _countersPerLevel
return &cs[i][j]
}
// fnv32a, adapted from "hash/fnv", but without a []byte(string) alloc
func fnv32a(s string) uint32 {
const (
offset32 = 2166136261
prime32 = 16777619
)
hash := uint32(offset32)
for i := 0; i < len(s); i++ {
hash ^= uint32(s[i])
hash *= prime32
}
return hash
}
func (c *counter) IncCheckReset(t time.Time, tick time.Duration) uint64 {
tn := t.UnixNano()
resetAfter := c.resetAt.Load()
if resetAfter > tn {
return c.counter.Inc()
}
c.counter.Store(1)
newResetAfter := tn + tick.Nanoseconds()
if !c.resetAt.CAS(resetAfter, newResetAfter) {
// We raced with another goroutine trying to reset, and it also reset
// the counter to 1, so we need to reincrement the counter.
return c.counter.Inc()
}
return 1
}
// SamplingDecision is a decision represented as a bit field made by sampler.
// More decisions may be added in the future.
type SamplingDecision uint32
const (
// LogDropped indicates that the Sampler dropped a log entry.
LogDropped SamplingDecision = 1 << iota
// LogSampled indicates that the Sampler sampled a log entry.
LogSampled
)
// optionFunc wraps a func so it satisfies the SamplerOption interface.
type optionFunc func(*sampler)
func (f optionFunc) apply(s *sampler) {
f(s)
}
// SamplerOption configures a Sampler.
type SamplerOption interface {
apply(*sampler)
}
// nopSamplingHook is the default hook used by sampler.
func nopSamplingHook(Entry, SamplingDecision) {}
// SamplerHook registers a function which will be called when Sampler makes a
// decision.
//
// This hook may be used to get visibility into the performance of the sampler.
// For example, use it to track metrics of dropped versus sampled logs.
//
// var dropped atomic.Int64
// zapcore.SamplerHook(func(ent zapcore.Entry, dec zapcore.SamplingDecision) {
// if dec&zapcore.LogDropped > 0 {
// dropped.Inc()
// }
// })
func SamplerHook(hook func(entry Entry, dec SamplingDecision)) SamplerOption {
return optionFunc(func(s *sampler) {
s.hook = hook
})
}
// NewSamplerWithOptions creates a Core that samples incoming entries, which
// caps the CPU and I/O load of logging while attempting to preserve a
// representative subset of your logs.
//
// Zap samples by logging the first N entries with a given level and message
// each tick. If more Entries with the same level and message are seen during
// the same interval, every Mth message is logged and the rest are dropped.
//
// For example,
//
// core = NewSamplerWithOptions(core, time.Second, 10, 5)
//
// This will log the first 10 log entries with the same level and message
// in a one second interval as-is. Following that, it will allow through
// every 5th log entry with the same level and message in that interval.
//
// If thereafter is zero, the Core will drop all log entries after the first N
// in that interval.
//
// Sampler can be configured to report sampling decisions with the SamplerHook
// option.
//
// Keep in mind that Zap's sampling implementation is optimized for speed over
// absolute precision; under load, each tick may be slightly over- or
// under-sampled.
func NewSamplerWithOptions(core Core, tick time.Duration, first, thereafter int, opts ...SamplerOption) Core {
s := &sampler{
Core: core,
tick: tick,
counts: newCounters(),
first: uint64(first),
thereafter: uint64(thereafter),
hook: nopSamplingHook,
}
for _, opt := range opts {
opt.apply(s)
}
return s
}
type sampler struct {
Core
counts *counters
tick time.Duration
first, thereafter uint64
hook func(Entry, SamplingDecision)
}
var (
_ Core = (*sampler)(nil)
_ leveledEnabler = (*sampler)(nil)
)
// NewSampler creates a Core that samples incoming entries, which
// caps the CPU and I/O load of logging while attempting to preserve a
// representative subset of your logs.
//
// Zap samples by logging the first N entries with a given level and message
// each tick. If more Entries with the same level and message are seen during
// the same interval, every Mth message is logged and the rest are dropped.
//
// Keep in mind that zap's sampling implementation is optimized for speed over
// absolute precision; under load, each tick may be slightly over- or
// under-sampled.
//
// Deprecated: use NewSamplerWithOptions.
func NewSampler(core Core, tick time.Duration, first, thereafter int) Core {
return NewSamplerWithOptions(core, tick, first, thereafter)
}
func (s *sampler) Level() Level {
return LevelOf(s.Core)
}
func (s *sampler) With(fields []Field) Core {
return &sampler{
Core: s.Core.With(fields),
tick: s.tick,
counts: s.counts,
first: s.first,
thereafter: s.thereafter,
hook: s.hook,
}
}
func (s *sampler) Check(ent Entry, ce *CheckedEntry) *CheckedEntry {
if !s.Enabled(ent.Level) {
return ce
}
if ent.Level >= _minLevel && ent.Level <= _maxLevel {
counter := s.counts.get(ent.Level, ent.Message)
n := counter.IncCheckReset(ent.Time, s.tick)
if n > s.first && (s.thereafter == 0 || (n-s.first)%s.thereafter != 0) {
s.hook(ent, LogDropped)
return ce
}
s.hook(ent, LogSampled)
}
return s.Core.Check(ent, ce)
}
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