Scott Baker | 2d89798 | 2019-09-24 11:50:08 -0700 | [diff] [blame^] | 1 | package metrics |
| 2 | |
| 3 | import "sync/atomic" |
| 4 | |
| 5 | // Counters hold an int64 value that can be incremented and decremented. |
| 6 | type Counter interface { |
| 7 | Clear() |
| 8 | Count() int64 |
| 9 | Dec(int64) |
| 10 | Inc(int64) |
| 11 | Snapshot() Counter |
| 12 | } |
| 13 | |
| 14 | // GetOrRegisterCounter returns an existing Counter or constructs and registers |
| 15 | // a new StandardCounter. |
| 16 | func GetOrRegisterCounter(name string, r Registry) Counter { |
| 17 | if nil == r { |
| 18 | r = DefaultRegistry |
| 19 | } |
| 20 | return r.GetOrRegister(name, NewCounter).(Counter) |
| 21 | } |
| 22 | |
| 23 | // NewCounter constructs a new StandardCounter. |
| 24 | func NewCounter() Counter { |
| 25 | if UseNilMetrics { |
| 26 | return NilCounter{} |
| 27 | } |
| 28 | return &StandardCounter{0} |
| 29 | } |
| 30 | |
| 31 | // NewRegisteredCounter constructs and registers a new StandardCounter. |
| 32 | func NewRegisteredCounter(name string, r Registry) Counter { |
| 33 | c := NewCounter() |
| 34 | if nil == r { |
| 35 | r = DefaultRegistry |
| 36 | } |
| 37 | r.Register(name, c) |
| 38 | return c |
| 39 | } |
| 40 | |
| 41 | // CounterSnapshot is a read-only copy of another Counter. |
| 42 | type CounterSnapshot int64 |
| 43 | |
| 44 | // Clear panics. |
| 45 | func (CounterSnapshot) Clear() { |
| 46 | panic("Clear called on a CounterSnapshot") |
| 47 | } |
| 48 | |
| 49 | // Count returns the count at the time the snapshot was taken. |
| 50 | func (c CounterSnapshot) Count() int64 { return int64(c) } |
| 51 | |
| 52 | // Dec panics. |
| 53 | func (CounterSnapshot) Dec(int64) { |
| 54 | panic("Dec called on a CounterSnapshot") |
| 55 | } |
| 56 | |
| 57 | // Inc panics. |
| 58 | func (CounterSnapshot) Inc(int64) { |
| 59 | panic("Inc called on a CounterSnapshot") |
| 60 | } |
| 61 | |
| 62 | // Snapshot returns the snapshot. |
| 63 | func (c CounterSnapshot) Snapshot() Counter { return c } |
| 64 | |
| 65 | // NilCounter is a no-op Counter. |
| 66 | type NilCounter struct{} |
| 67 | |
| 68 | // Clear is a no-op. |
| 69 | func (NilCounter) Clear() {} |
| 70 | |
| 71 | // Count is a no-op. |
| 72 | func (NilCounter) Count() int64 { return 0 } |
| 73 | |
| 74 | // Dec is a no-op. |
| 75 | func (NilCounter) Dec(i int64) {} |
| 76 | |
| 77 | // Inc is a no-op. |
| 78 | func (NilCounter) Inc(i int64) {} |
| 79 | |
| 80 | // Snapshot is a no-op. |
| 81 | func (NilCounter) Snapshot() Counter { return NilCounter{} } |
| 82 | |
| 83 | // StandardCounter is the standard implementation of a Counter and uses the |
| 84 | // sync/atomic package to manage a single int64 value. |
| 85 | type StandardCounter struct { |
| 86 | count int64 |
| 87 | } |
| 88 | |
| 89 | // Clear sets the counter to zero. |
| 90 | func (c *StandardCounter) Clear() { |
| 91 | atomic.StoreInt64(&c.count, 0) |
| 92 | } |
| 93 | |
| 94 | // Count returns the current count. |
| 95 | func (c *StandardCounter) Count() int64 { |
| 96 | return atomic.LoadInt64(&c.count) |
| 97 | } |
| 98 | |
| 99 | // Dec decrements the counter by the given amount. |
| 100 | func (c *StandardCounter) Dec(i int64) { |
| 101 | atomic.AddInt64(&c.count, -i) |
| 102 | } |
| 103 | |
| 104 | // Inc increments the counter by the given amount. |
| 105 | func (c *StandardCounter) Inc(i int64) { |
| 106 | atomic.AddInt64(&c.count, i) |
| 107 | } |
| 108 | |
| 109 | // Snapshot returns a read-only copy of the counter. |
| 110 | func (c *StandardCounter) Snapshot() Counter { |
| 111 | return CounterSnapshot(c.Count()) |
| 112 | } |