1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
|
package hmetrics
import (
"bytes"
"context"
"encoding/json"
"fmt"
"net/http"
"os"
"runtime"
"sync"
"time"
)
const (
metricWaitTime = 20 * time.Second
)
var (
DefaultEndpoint string
)
func init() {
DefaultEndpoint = os.Getenv("HEROKU_METRICS_URL")
}
type AlreadyStarted struct{}
func (as AlreadyStarted) Error() string {
return "already started"
}
func (as AlreadyStarted) Fatal() bool {
return false
}
type HerokuMetricsURLUnset struct{}
func (e HerokuMetricsURLUnset) Error() string {
return "cannot report metrics because HEROKU_METRICS_URL is unset"
}
func (e HerokuMetricsURLUnset) Fatal() bool {
return true
}
var (
mu sync.Mutex
started bool
)
// ErrHandler receives any errors encountered during collection or reporting of metrics to Heroku. Processing of metrics
// continues if the ErrHandler returns nil, but aborts if the ErrHandler itself returns an error.
type ErrHandler func(err error) error
func Report(ctx context.Context, ef ErrHandler) error {
mu.Lock()
defer mu.Unlock()
if started {
return AlreadyStarted{}
}
endpoint := DefaultEndpoint
if endpoint == "" {
return HerokuMetricsURLUnset{}
}
if ef == nil {
ef = func(_ error) error { return nil }
}
go report(ctx, endpoint, ef)
started = true
return nil
}
// The only thing that should come after an exit() is a return.
// Best to use in a function that can defer it.
func exit() {
mu.Lock()
defer mu.Unlock()
started = false
}
func report(ctx context.Context, endpoint string, ef ErrHandler) {
defer exit()
t := time.NewTicker(metricWaitTime)
defer t.Stop()
for {
select {
case <-t.C:
case <-ctx.Done():
return
}
if err := gatherMetrics(); err != nil {
if err := ef(err); err != nil {
return
}
continue
}
if err := submitPayload(ctx, endpoint); err != nil {
if err := ef(err); err != nil {
return
}
continue
}
}
}
var (
lastGCPause uint64
lastNumGC uint32
buf bytes.Buffer
)
// TODO: If we ever have high frequency charts HeapIdle minus HeapReleased could be interesting.
func gatherMetrics() error {
var stats runtime.MemStats
runtime.ReadMemStats(&stats)
// cribbed from https://github.com/codahale/metrics/blob/master/runtime/memstats.go
pauseNS := stats.PauseTotalNs - lastGCPause
lastGCPause = stats.PauseTotalNs
numGC := stats.NumGC - lastNumGC
lastNumGC = stats.NumGC
result := struct {
Counters map[string]float64 `json:"counters"`
Gauges map[string]float64 `json:"gauges"`
}{
Counters: map[string]float64{
"go.gc.collections": float64(numGC),
"go.gc.pause.ns": float64(pauseNS),
},
Gauges: map[string]float64{
"go.memory.heap.bytes": float64(stats.Alloc),
"go.memory.stack.bytes": float64(stats.StackInuse),
"go.memory.heap.objects": float64(stats.Mallocs - stats.Frees), // Number of "live" objects.
"go.gc.goal": float64(stats.NextGC), // Goal heap size for next GC.
"go.routines": float64(runtime.NumGoroutine()), // Current number of goroutines.
},
}
buf.Reset()
return json.NewEncoder(&buf).Encode(result)
}
func submitPayload(ctx context.Context, where string) error {
req, err := http.NewRequest("POST", where, &buf)
if err != nil {
return err
}
req = req.WithContext(ctx)
req.Header.Add("Content-Type", "application/json")
resp, err := http.DefaultClient.Do(req)
if err != nil {
return err
}
defer resp.Body.Close()
if resp.StatusCode != http.StatusOK {
return fmt.Errorf("expected %v (http.StatusOK) but got %s", http.StatusOK, resp.Status)
}
return nil
}
|
