Matteo Scandolo | a428586 | 2020-12-01 18:10:10 -0800 | [diff] [blame] | 1 | // Copyright (c) 2016 Uber Technologies, Inc. |
| 2 | // |
| 3 | // Permission is hereby granted, free of charge, to any person obtaining a copy |
| 4 | // of this software and associated documentation files (the "Software"), to deal |
| 5 | // in the Software without restriction, including without limitation the rights |
| 6 | // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell |
| 7 | // copies of the Software, and to permit persons to whom the Software is |
| 8 | // furnished to do so, subject to the following conditions: |
| 9 | // |
| 10 | // The above copyright notice and this permission notice shall be included in |
| 11 | // all copies or substantial portions of the Software. |
| 12 | // |
| 13 | // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
| 14 | // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
| 15 | // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
| 16 | // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
| 17 | // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, |
| 18 | // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN |
| 19 | // THE SOFTWARE. |
| 20 | |
| 21 | package zapcore |
| 22 | |
| 23 | import ( |
| 24 | "time" |
| 25 | |
| 26 | "go.uber.org/atomic" |
| 27 | ) |
| 28 | |
| 29 | const ( |
| 30 | _numLevels = _maxLevel - _minLevel + 1 |
| 31 | _countersPerLevel = 4096 |
| 32 | ) |
| 33 | |
| 34 | type counter struct { |
| 35 | resetAt atomic.Int64 |
| 36 | counter atomic.Uint64 |
| 37 | } |
| 38 | |
| 39 | type counters [_numLevels][_countersPerLevel]counter |
| 40 | |
| 41 | func newCounters() *counters { |
| 42 | return &counters{} |
| 43 | } |
| 44 | |
| 45 | func (cs *counters) get(lvl Level, key string) *counter { |
| 46 | i := lvl - _minLevel |
| 47 | j := fnv32a(key) % _countersPerLevel |
| 48 | return &cs[i][j] |
| 49 | } |
| 50 | |
| 51 | // fnv32a, adapted from "hash/fnv", but without a []byte(string) alloc |
| 52 | func fnv32a(s string) uint32 { |
| 53 | const ( |
| 54 | offset32 = 2166136261 |
| 55 | prime32 = 16777619 |
| 56 | ) |
| 57 | hash := uint32(offset32) |
| 58 | for i := 0; i < len(s); i++ { |
| 59 | hash ^= uint32(s[i]) |
| 60 | hash *= prime32 |
| 61 | } |
| 62 | return hash |
| 63 | } |
| 64 | |
| 65 | func (c *counter) IncCheckReset(t time.Time, tick time.Duration) uint64 { |
| 66 | tn := t.UnixNano() |
| 67 | resetAfter := c.resetAt.Load() |
| 68 | if resetAfter > tn { |
| 69 | return c.counter.Inc() |
| 70 | } |
| 71 | |
| 72 | c.counter.Store(1) |
| 73 | |
| 74 | newResetAfter := tn + tick.Nanoseconds() |
| 75 | if !c.resetAt.CAS(resetAfter, newResetAfter) { |
| 76 | // We raced with another goroutine trying to reset, and it also reset |
| 77 | // the counter to 1, so we need to reincrement the counter. |
| 78 | return c.counter.Inc() |
| 79 | } |
| 80 | |
| 81 | return 1 |
| 82 | } |
| 83 | |
| 84 | type sampler struct { |
| 85 | Core |
| 86 | |
| 87 | counts *counters |
| 88 | tick time.Duration |
| 89 | first, thereafter uint64 |
| 90 | } |
| 91 | |
| 92 | // NewSampler creates a Core that samples incoming entries, which caps the CPU |
| 93 | // and I/O load of logging while attempting to preserve a representative subset |
| 94 | // of your logs. |
| 95 | // |
| 96 | // Zap samples by logging the first N entries with a given level and message |
| 97 | // each tick. If more Entries with the same level and message are seen during |
| 98 | // the same interval, every Mth message is logged and the rest are dropped. |
| 99 | // |
| 100 | // Keep in mind that zap's sampling implementation is optimized for speed over |
| 101 | // absolute precision; under load, each tick may be slightly over- or |
| 102 | // under-sampled. |
| 103 | func NewSampler(core Core, tick time.Duration, first, thereafter int) Core { |
| 104 | return &sampler{ |
| 105 | Core: core, |
| 106 | tick: tick, |
| 107 | counts: newCounters(), |
| 108 | first: uint64(first), |
| 109 | thereafter: uint64(thereafter), |
| 110 | } |
| 111 | } |
| 112 | |
| 113 | func (s *sampler) With(fields []Field) Core { |
| 114 | return &sampler{ |
| 115 | Core: s.Core.With(fields), |
| 116 | tick: s.tick, |
| 117 | counts: s.counts, |
| 118 | first: s.first, |
| 119 | thereafter: s.thereafter, |
| 120 | } |
| 121 | } |
| 122 | |
| 123 | func (s *sampler) Check(ent Entry, ce *CheckedEntry) *CheckedEntry { |
| 124 | if !s.Enabled(ent.Level) { |
| 125 | return ce |
| 126 | } |
| 127 | |
| 128 | counter := s.counts.get(ent.Level, ent.Message) |
| 129 | n := counter.IncCheckReset(ent.Time, s.tick) |
| 130 | if n > s.first && (n-s.first)%s.thereafter != 0 { |
| 131 | return ce |
| 132 | } |
| 133 | return s.Core.Check(ent, ce) |
| 134 | } |