Add simple scroll test

recipes/scroll/.gitignore

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+/scroll

recipes/scroll/scroll.go

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+// Copyright 2012-present Oliver Eilhard. All rights reserved.
+// Use of this source code is governed by a MIT-license.
+// See http://olivere.mit-license.org/license.txt for details.
+
+// Scroll illustrates scrolling through a set of documents.
+//
+// Example
+//
+// Scroll through an index called "products".
+// Use "_uid" as the default field:
+//
+//     scroll -index=products -size=100
+//
+package main
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"io"
+	"log"
+	"sync/atomic"
+	"time"
+
+	"golang.org/x/sync/errgroup"
+
+	"github.com/olivere/elastic"
+)
+
+func main() {
+	var (
+		url   = flag.String("url", "http://localhost:9200", "Elasticsearch URL")
+		index = flag.String("index", "", "Elasticsearch index name")
+		typ   = flag.String("type", "", "Elasticsearch type name")
+		size  = flag.Int("size", 100, "Slice of documents to get per scroll")
+		sniff = flag.Bool("sniff", true, "Enable or disable sniffing")
+	)
+	flag.Parse()
+	log.SetFlags(0)
+
+	if *url == "" {
+		log.Fatal("missing url parameter")
+	}
+	if *index == "" {
+		log.Fatal("missing index parameter")
+	}
+	if *size <= 0 {
+		log.Fatal("size must be greater than zero")
+	}
+
+	// Create an Elasticsearch client
+	client, err := elastic.NewClient(elastic.SetURL(*url), elastic.SetSniff(*sniff))
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Setup a group of goroutines from the excellent errgroup package
+	g, ctx := errgroup.WithContext(context.TODO())
+
+	// Hits channel will be sent to from the first set of goroutines and consumed by the second
+	type hit struct {
+		Slice int
+		Hit   elastic.SearchHit
+	}
+	hitsc := make(chan hit)
+
+	begin := time.Now()
+
+	// Start goroutine for this sliced scroll
+	g.Go(func() error {
+		defer close(hitsc)
+
+		// Prepare the query
+		var query elastic.Query
+		if *typ == "" {
+			query = elastic.NewMatchAllQuery()
+		} else {
+			query = elastic.NewTypeQuery(*typ)
+		}
+		svc := client.Scroll(*index).Query(query)
+		for {
+			res, err := svc.Do(ctx)
+			if err == io.EOF {
+				break
+			}
+			if err != nil {
+				return err
+			}
+			for _, searchHit := range res.Hits.Hits {
+				// Pass the hit to the hits channel, which will be consumed below
+				select {
+				case hitsc <- hit{Hit: *searchHit}:
+				case <-ctx.Done():
+					return ctx.Err()
+				}
+			}
+		}
+		return nil
+	})
+
+	// Second goroutine will consume the hits sent from the workers in first set of goroutines
+	var total uint64
+	g.Go(func() error {
+		for range hitsc {
+			// We simply count the hits here.
+			current := atomic.AddUint64(&total, 1)
+			sec := int(time.Since(begin).Seconds())
+			fmt.Printf("%8d | %02d:%02d\r", current, sec/60, sec%60)
+			select {
+			default:
+			case <-ctx.Done():
+				return ctx.Err()
+			}
+		}
+		return nil
+	})
+
+	// Wait until all goroutines are finished
+	if err := g.Wait(); err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Printf("Scrolled through a total of %d documents in %v\n", total, time.Since(begin))
+}