98 lines
2.5 KiB
Markdown
98 lines
2.5 KiB
Markdown
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# package metrics
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`package metrics` provides a set of uniform interfaces for service instrumentation.
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It has
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[counters](http://prometheus.io/docs/concepts/metric_types/#counter),
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[gauges](http://prometheus.io/docs/concepts/metric_types/#gauge), and
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[histograms](http://prometheus.io/docs/concepts/metric_types/#histogram),
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and provides adapters to popular metrics packages, like
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[expvar](https://golang.org/pkg/expvar),
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[StatsD](https://github.com/etsy/statsd), and
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[Prometheus](https://prometheus.io).
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## Rationale
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Code instrumentation is absolutely essential to achieve
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[observability](https://speakerdeck.com/mattheath/observability-in-micro-service-architectures)
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into a distributed system.
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Metrics and instrumentation tools have coalesced around a few well-defined idioms.
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`package metrics` provides a common, minimal interface those idioms for service authors.
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## Usage
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A simple counter, exported via expvar.
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```go
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import (
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"github.com/go-kit/kit/metrics"
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"github.com/go-kit/kit/metrics/expvar"
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)
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func main() {
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var myCount metrics.Counter
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myCount = expvar.NewCounter("my_count")
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myCount.Add(1)
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}
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```
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A histogram for request duration,
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exported via a Prometheus summary with dynamically-computed quantiles.
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```go
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import (
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"time"
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stdprometheus "github.com/prometheus/client_golang/prometheus"
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"github.com/go-kit/kit/metrics"
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"github.com/go-kit/kit/metrics/prometheus"
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)
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func main() {
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var dur metrics.Histogram = prometheus.NewSummaryFrom(stdprometheus.SummaryOpts{
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Namespace: "myservice",
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Subsystem: "api",
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Name: "request_duration_seconds",
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Help: "Total time spent serving requests.",
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}, []string{})
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// ...
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}
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func handleRequest(dur metrics.Histogram) {
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defer func(begin time.Time) { dur.Observe(time.Since(begin).Seconds()) }(time.Now())
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// handle request
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}
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```
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A gauge for the number of goroutines currently running, exported via StatsD.
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```go
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import (
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"net"
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"os"
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"runtime"
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"time"
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"github.com/go-kit/kit/metrics"
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"github.com/go-kit/kit/metrics/statsd"
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)
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func main() {
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statsd := statsd.New("foo_svc.", log.NewNopLogger())
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report := time.NewTicker(5 * time.Second)
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defer report.Stop()
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go statsd.SendLoop(report.C, "tcp", "statsd.internal:8125")
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goroutines := statsd.NewGauge("goroutine_count")
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go exportGoroutines(goroutines)
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// ...
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}
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func exportGoroutines(g metrics.Gauge) {
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for range time.Tick(time.Second) {
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g.Set(float64(runtime.NumGoroutine()))
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}
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}
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```
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For more information, see [the package documentation](https://godoc.org/github.com/go-kit/kit/metrics).
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