blob: bb7b039cb5725de5af2fd8a9b2096418e2cbe225 [file] [log] [blame]
Pragya Arya324337e2020-02-20 14:35:08 +05301package metrics
2
3import "sync/atomic"
4
5// Counters hold an int64 value that can be incremented and decremented.
6type 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.
16func 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.
24func NewCounter() Counter {
25 if UseNilMetrics {
26 return NilCounter{}
27 }
28 return &StandardCounter{0}
29}
30
31// NewRegisteredCounter constructs and registers a new StandardCounter.
32func 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.
42type CounterSnapshot int64
43
44// Clear panics.
45func (CounterSnapshot) Clear() {
46 panic("Clear called on a CounterSnapshot")
47}
48
49// Count returns the count at the time the snapshot was taken.
50func (c CounterSnapshot) Count() int64 { return int64(c) }
51
52// Dec panics.
53func (CounterSnapshot) Dec(int64) {
54 panic("Dec called on a CounterSnapshot")
55}
56
57// Inc panics.
58func (CounterSnapshot) Inc(int64) {
59 panic("Inc called on a CounterSnapshot")
60}
61
62// Snapshot returns the snapshot.
63func (c CounterSnapshot) Snapshot() Counter { return c }
64
65// NilCounter is a no-op Counter.
66type NilCounter struct{}
67
68// Clear is a no-op.
69func (NilCounter) Clear() {}
70
71// Count is a no-op.
72func (NilCounter) Count() int64 { return 0 }
73
74// Dec is a no-op.
75func (NilCounter) Dec(i int64) {}
76
77// Inc is a no-op.
78func (NilCounter) Inc(i int64) {}
79
80// Snapshot is a no-op.
81func (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.
85type StandardCounter struct {
86 count int64
87}
88
89// Clear sets the counter to zero.
90func (c *StandardCounter) Clear() {
91 atomic.StoreInt64(&c.count, 0)
92}
93
94// Count returns the current count.
95func (c *StandardCounter) Count() int64 {
96 return atomic.LoadInt64(&c.count)
97}
98
99// Dec decrements the counter by the given amount.
100func (c *StandardCounter) Dec(i int64) {
101 atomic.AddInt64(&c.count, -i)
102}
103
104// Inc increments the counter by the given amount.
105func (c *StandardCounter) Inc(i int64) {
106 atomic.AddInt64(&c.count, i)
107}
108
109// Snapshot returns a read-only copy of the counter.
110func (c *StandardCounter) Snapshot() Counter {
111 return CounterSnapshot(c.Count())
112}