Initial delivery of metrics code (#81)

* Initial delivery of metrics code

* Fix build issues

* Fix build issue with go vet

vendor/github.com/beorn7/perks/quantile/example_test.go

@@ -0,0 +1,121 @@
+// +build go1.1
+
+package quantile_test
+
+import (
+	"bufio"
+	"fmt"
+	"log"
+	"os"
+	"strconv"
+	"time"
+
+	"github.com/beorn7/perks/quantile"
+)
+
+func Example_simple() {
+	ch := make(chan float64)
+	go sendFloats(ch)
+
+	// Compute the 50th, 90th, and 99th percentile.
+	q := quantile.NewTargeted(map[float64]float64{
+		0.50: 0.005,
+		0.90: 0.001,
+		0.99: 0.0001,
+	})
+	for v := range ch {
+		q.Insert(v)
+	}
+
+	fmt.Println("perc50:", q.Query(0.50))
+	fmt.Println("perc90:", q.Query(0.90))
+	fmt.Println("perc99:", q.Query(0.99))
+	fmt.Println("count:", q.Count())
+	// Output:
+	// perc50: 5
+	// perc90: 16
+	// perc99: 223
+	// count: 2388
+}
+
+func Example_mergeMultipleStreams() {
+	// Scenario:
+	// We have multiple database shards. On each shard, there is a process
+	// collecting query response times from the database logs and inserting
+	// them into a Stream (created via NewTargeted(0.90)), much like the
+	// Simple example. These processes expose a network interface for us to
+	// ask them to serialize and send us the results of their
+	// Stream.Samples so we may Merge and Query them.
+	//
+	// NOTES:
+	// * These sample sets are small, allowing us to get them
+	// across the network much faster than sending the entire list of data
+	// points.
+	//
+	// * For this to work correctly, we must supply the same quantiles
+	// a priori the process collecting the samples supplied to NewTargeted,
+	// even if we do not plan to query them all here.
+	ch := make(chan quantile.Samples)
+	getDBQuerySamples(ch)
+	q := quantile.NewTargeted(map[float64]float64{0.90: 0.001})
+	for samples := range ch {
+		q.Merge(samples)
+	}
+	fmt.Println("perc90:", q.Query(0.90))
+}
+
+func Example_window() {
+	// Scenario: We want the 90th, 95th, and 99th percentiles for each
+	// minute.
+
+	ch := make(chan float64)
+	go sendStreamValues(ch)
+
+	tick := time.NewTicker(1 * time.Minute)
+	q := quantile.NewTargeted(map[float64]float64{
+		0.90: 0.001,
+		0.95: 0.0005,
+		0.99: 0.0001,
+	})
+	for {
+		select {
+		case t := <-tick.C:
+			flushToDB(t, q.Samples())
+			q.Reset()
+		case v := <-ch:
+			q.Insert(v)
+		}
+	}
+}
+
+func sendStreamValues(ch chan float64) {
+	// Use your imagination
+}
+
+func flushToDB(t time.Time, samples quantile.Samples) {
+	// Use your imagination
+}
+
+// This is a stub for the above example. In reality this would hit the remote
+// servers via http or something like it.
+func getDBQuerySamples(ch chan quantile.Samples) {}
+
+func sendFloats(ch chan<- float64) {
+	f, err := os.Open("exampledata.txt")
+	if err != nil {
+		log.Fatal(err)
+	}
+	sc := bufio.NewScanner(f)
+	for sc.Scan() {
+		b := sc.Bytes()
+		v, err := strconv.ParseFloat(string(b), 64)
+		if err != nil {
+			log.Fatal(err)
+		}
+		ch <- v
+	}
+	if sc.Err() != nil {
+		log.Fatal(sc.Err())
+	}
+	close(ch)
+}