GSI indexes: high CPU utilization after load-cycle

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.concurrent.Phaser;

public class BombardaMaxima extends Thread {

    private final int tid;

    // configure here

    private static final int threads = 20;

    private static final int docsPerThread = 50000;

    private static final int docTTLms = 86400 * 1000;

    private static final int dumpToConsoleEachNDocs = 1000;

    private static final Phaser phaser = new Phaser(threads + 1);

    private static final CouchbaseEnvironment ce;

    private static final Cluster cluster;

    private static final String bucket = "default";

    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);

        // three indexes for query

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

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

        final String iQC = "CREATE INDEX iQC 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";

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

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

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

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

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

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

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

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

    }

    public BombardaMaxima(final int tid) {

        this.tid = tid;

    }

    public final void run() {

        try {

            Bucket b = null;

            synchronized(cluster) { b = cluster.openBucket(bucket); }

            final long stm = System.currentTimeMillis();

            final JsonObject jo = JsonObject

                    .empty()

                    .put("a", stm)

                    .put("b", stm)

                    .put("c", stm);

            for(int i = 0; i< docsPerThread; i++) { 

                b.upsert(JsonDocument.create(

                        tid + ":" + System.currentTimeMillis(), 

                        (int)((System.currentTimeMillis() + docTTLms) / 1000),

                        jo)

                );

                if (i % dumpToConsoleEachNDocs == 0) System.out.println("T[" + tid + "] = " + i);

            }

        } catch(final Exception e) {

            e.printStackTrace();

        } finally {

            phaser.arriveAndAwaitAdvance();

        }   

    }

    public static void main(String[] args) {

        for(int i = 0; i< threads; i++) new BombardaMaxima(i).start();

        phaser.arriveAndAwaitAdvance();

        System.out.println("DONE");

    }

}