-patan a small library for gathering metrics.

Golang port of the java sampling library patan that provides:

• counters; keeping track of how many times something has taken place
• sampling; collecting samples and describing their distribution
• durations; measuring the duration of a task as a special case of sampling

The API is not identical to the java version, some methods are named differently.

When serializing a snapshot to JSON, it should produce the same output as the java version.

Start with:

    go get gopkg.in/toefel18/go-patan.v1/metrics

Documentation: godoc.org/github.com/toefel18/go-patan/metrics

Usage:

package main

import (
    "github.com/toefel18/go-patan/metrics"
    "time"
    "fmt"
    "encoding/json"
)

func main() {
    stopwatch := metrics.StartStopwatch()
    time.Sleep(2 * time.Second)

    metrics.AddSample("mem.allocations", 167.0334)
    metrics.AddSample("mem.allocations", 111.9216)
    metrics.AddSample("mem.allocations", 133.4686)
    metrics.AddSample("mem.collects", 2)
    metrics.AddToCounter("active.sessions", 132)
    metrics.DecrementCounter("active.sessions")
    metrics.RecordElapsedTime("my.heavy.operation", stopwatch)   
    snapshot := metrics.Snapshot()                               

    duration, exists := snapshot.Durations()["my.heavy.operation"]
    if exists {
        fmt.Print("duration has sample count of ", duration.SampleCount()) // samplecount = 1
    } else {
        fmt.Print("duration does not exist")
    }

    // JSONizing a snapshot that can be published through REST
    if json, err := json.MarshalIndent(snapshot, "", "  "); err == nil {
        fmt.Println(string(json))
    }
}

The output will be:

{
  "timestampStarted": 1480792554683,
  "timestampTaken": 1480792556683,
  "durations": {
    "my.heavy.operation": {
      "sampleCount": 1,
      "minimum": 2000.129942,
      "maximum": 2000.129942,
      "mean": 2000.129942,
      "stdDeviation": 0
    }
  },
  "counters": {
    "active.sessions": 131
  },
  "samples": {
    "mem.allocations": {
      "sampleCount": 3,
      "minimum": 111.9216,
      "maximum": 167.0334,
      "mean": 137.47453333333334,
      "stdDeviation": 27.77342707001304
    },
    "mem.collects": {
      "sampleCount": 1,
      "minimum": 2,
      "maximum": 2,
      "mean": 2,
      "stdDeviation": 0
    }
  }
}

metrics is the default metrics instance, which is always and directly available when using patan. It's also possible to create multiple instances of metrics, which could be useful to separate detailed and global measurements or public/private measurements.

package main

import (
    "github.com/toefel18/go-patan/metrics"
    "net/http"
    "fmt"
    "html"
)

func main() {
    apiMetrics := metrics.New()
    dbMetrics := metrics.New()
    
    http.HandleFunc("/music/songs", func(w http.ResponseWriter, r *http.Request) {
        apiMetrics.MeasureFunc("api.music.songs", func () {
    	    fmt.Fprintf(w, "Hello, %q", html.EscapeString(r.URL.Path))
        })
    })
    
    // or
    http.HandleFunc("/music/albums", func(w http.ResponseWriter, r *http.Request) {
        stopwatch := metrics.StartStopwatch()
        
        data := "some database operation"
        dbMetrics.RecordElapsedTime("db.music.albums", stopwatch)   // stopwatch is not bound to a specific instance!
                    
    	fmt.Fprintf(w, "Hello, %q " + data, html.EscapeString(r.URL.Path))    	
    	apiMetrics.RecordElapsedTime("api.music.albums", stopwatch)
    })  
}