GSI: index fragmentation up to 90% possible with simple upsertions

package highcpuafterload;

import com.couchbase.client.java.Bucket;

import com.couchbase.client.java.Cluster;

import com.couchbase.client.java.CouchbaseCluster;

import com.couchbase.client.java.document.JsonDocument;

import com.couchbase.client.java.document.json.JsonObject;

import com.couchbase.client.java.env.CouchbaseEnvironment;

import com.couchbase.client.java.env.DefaultCouchbaseEnvironment;

import com.couchbase.client.java.query.N1qlQuery;

import java.util.LinkedList;

import java.util.Scanner;

import java.util.concurrent.Phaser;

import java.util.concurrent.ThreadLocalRandom;

public class BombardaMaxima extends Thread {

    private static final CouchbaseEnvironment ce;

    private static final Cluster cluster;

    private static final String bucket = "default";

    // configure here

    private static final int indexableInsertions = 1;

    private static final int nonIndexableInsertions = 1;

    private static final int totalRuns = 10000;

    static {

        ce = DefaultCouchbaseEnvironment.create();

        final LinkedList<String> nodes = new LinkedList();

        nodes.add("A.node");

        nodes.add("B.node");

        nodes.add("C.node");

        cluster = CouchbaseCluster.create(ce, nodes);

        final Bucket b = cluster.openBucket(bucket);

        final String iQA = "CREATE INDEX iQA ON `default`(a, b) WHERE a is valued USING GSI";

        final String iQX = "CREATE INDEX iQX ON `default`(a, c) WHERE a is valued USING GSI";

        b.query(N1qlQuery.simple(iQA));        

        b.query(N1qlQuery.simple(iQX));        

    }

    public static final JsonDocument makeDoc(String a, String b, String c) {

        return JsonDocument

                .create(

                    String.valueOf(ThreadLocalRandom.current().nextInt()),

                    JsonObject.empty()

                        .put(a, ThreadLocalRandom.current().nextInt())

                        .put(b, ThreadLocalRandom.current().nextInt())

                        .put(c, ThreadLocalRandom.current().nextInt())

                );

    }

    public static final void makeFragmentation(Bucket b, int n , boolean pause) {

        System.out.println("[" + n +"] inserting " + nonIndexableInsertions +" non-indexable documents");

        for(int i = 0; i < nonIndexableInsertions; i++) b.upsert(makeDoc("x", "y", "z"));

        if(pause) {

            System.out.println("press 'Enter' after checking fragmentation rate ...");

            Scanner s = new Scanner(System.in);

            s.nextLine();

        }    

        System.out.println("[" + n +"] inserting " + indexableInsertions + " indexable documents");

        for(int i = 0; i < indexableInsertions; i++)  b.upsert(makeDoc("a", "b", "c"));

        System.out.println("... check fragmentation rate");

    }

    public static void main(String[] args) {

        Bucket b = null;

        b = cluster.openBucket(bucket);

        for(int i = 0; i< totalRuns; i++) makeFragmentation(b, i,  false);

    }

}