/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.zookeeper.server;

import static org.apache.zookeeper.test.ClientBase.CONNECTION_TIMEOUT;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;
import java.io.File;
import java.io.IOException;
import java.util.Map;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.PortAssignment;
import org.apache.zookeeper.ZKTestCase;
import org.apache.zookeeper.ZooDefs;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.metrics.MetricsUtils;
import org.apache.zookeeper.test.ClientBase;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class RequestThrottlerTest extends ZKTestCase {

    private static final Logger LOG = LoggerFactory.getLogger(RequestThrottlerTest.class);

    private static String HOSTPORT = "127.0.0.1:" + PortAssignment.unique();
    private static final int TOTAL_REQUESTS = 5;
    private static final int STALL_TIME = 5000;

    // latch to hold requests in the PrepRequestProcessor to
    // keep them from going down the pipeline to reach the final
    // request processor, where the number of in process requests
    // will be decreased
    CountDownLatch resumeProcess = null;

    // latch to make sure all requests are submitted
    CountDownLatch submitted = null;

    // latch to make sure all requests entered the pipeline
    CountDownLatch entered = null;

    ZooKeeperServer zks = null;
    ServerCnxnFactory f = null;
    ZooKeeper zk = null;

    @Before
    public void setup() throws Exception {
        // start a server and create a client
        File tmpDir = ClientBase.createTmpDir();
        ClientBase.setupTestEnv();
        zks = new TestZooKeeperServer(tmpDir, tmpDir, 3000);
        final int PORT = Integer.parseInt(HOSTPORT.split(":")[1]);
        f = ServerCnxnFactory.createFactory(PORT, -1);
        f.startup(zks);
        LOG.info("starting up the zookeeper server .. waiting");
        assertTrue("waiting for server being up", ClientBase.waitForServerUp(HOSTPORT, CONNECTION_TIMEOUT));

        resumeProcess = null;
        submitted = null;

        zk = ClientBase.createZKClient(HOSTPORT);
    }

    @After
    public void tearDown() throws Exception {
        // shut down the server and the client
        if (null != zk) {
            zk.close();
        }

        if (null != f) {
            f.shutdown();
        }
        if (null != zks) {
            zks.shutdown();
        }
    }

    // TestZooKeeperServer
    // 1. uses our version of PrepRequestProcessor, which can hold the request as long as we want
    // 2. count the number of submitted requests
    class TestZooKeeperServer extends ZooKeeperServer {

        public TestZooKeeperServer(File snapDir, File logDir, int tickTime) throws IOException {
            super(snapDir, logDir, tickTime);
        }

        @Override
        protected void setupRequestProcessors() {
            RequestProcessor finalProcessor = new FinalRequestProcessor(this);
            RequestProcessor syncProcessor = new SyncRequestProcessor(this, finalProcessor);
            ((SyncRequestProcessor) syncProcessor).start();
            firstProcessor = new TestPrepRequestProcessor(this, syncProcessor);
            ((TestPrepRequestProcessor) firstProcessor).start();
        }

        @Override
        public void submitRequest(Request si) {
            if (null != submitted) {
                submitted.countDown();
            }
            super.submitRequest(si);
        }

    }

    class TestPrepRequestProcessor extends PrepRequestProcessor {

        public TestPrepRequestProcessor(ZooKeeperServer zks, RequestProcessor syncProcessor) {
            super(zks, syncProcessor);
        }

        @Override
        protected void pRequest(Request request) throws RequestProcessorException {
            // keep the request in the processor as long as we want
            if (resumeProcess != null) {
                try {
                    resumeProcess.await(20, TimeUnit.SECONDS);
                } catch (Exception e) {

                }
            }

            if (entered != null) {
                entered.countDown();
            }

            super.pRequest(request);
        }

    }

    @Test
    public void testRequestThrottler() throws Exception {
        ServerMetrics.getMetrics().resetAll();

        // we only allow two requests in the pipeline
        RequestThrottler.setMaxRequests(2);

        RequestThrottler.setStallTime(STALL_TIME);
        RequestThrottler.setDropStaleRequests(false);

        // no requests can go through the pipeline unless we raise the latch
        resumeProcess = new CountDownLatch(1);
        submitted = new CountDownLatch(TOTAL_REQUESTS);
        entered = new CountDownLatch(TOTAL_REQUESTS);

        // send 5 requests asynchronously
        for (int i = 0; i < TOTAL_REQUESTS; i++) {
            zk.create("/request_throttle_test- " + i, ("/request_throttle_test- "
                                                               + i).getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT, (rc, path, ctx, name) -> {
            }, null);
        }

        // make sure the server received all 5 requests
        submitted.await(5, TimeUnit.SECONDS);
        Map<String, Object> metrics = MetricsUtils.currentServerMetrics();

        // but only two requests can get into the pipeline because of the throttler
        assertEquals(2L, (long) metrics.get("prep_processor_request_queued"));
        assertEquals(1L, (long) metrics.get("request_throttle_wait_count"));

        // let the requests go through the pipeline and the throttler will be waken up to allow more requests
        // to enter the pipeline
        resumeProcess.countDown();
        entered.await(STALL_TIME, TimeUnit.MILLISECONDS);

        metrics = MetricsUtils.currentServerMetrics();
        assertEquals(TOTAL_REQUESTS, (long) metrics.get("prep_processor_request_queued"));
    }

    @Test
    public void testDropStaleRequests() throws Exception {
        ServerMetrics.getMetrics().resetAll();

        // we only allow two requests in the pipeline
        RequestThrottler.setMaxRequests(2);

        RequestThrottler.setStallTime(STALL_TIME);

        RequestThrottler.setDropStaleRequests(true);

        // no requests can go through the pipeline unless we raise the latch
        resumeProcess = new CountDownLatch(1);
        submitted = new CountDownLatch(TOTAL_REQUESTS);

        // send 5 requests asynchronously
        for (int i = 0; i < TOTAL_REQUESTS; i++) {
            zk.create("/request_throttle_test- " + i, ("/request_throttle_test- "
                                                               + i).getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT, (rc, path, ctx, name) -> {
            }, null);
        }

        // make sure the server received all 5 requests
        submitted.await(5, TimeUnit.SECONDS);
        Map<String, Object> metrics = MetricsUtils.currentServerMetrics();

        // but only two requests can get into the pipeline because of the throttler
        assertEquals(2L, (long) metrics.get("prep_processor_request_queued"));
        assertEquals(1L, (long) metrics.get("request_throttle_wait_count"));

        for (ServerCnxn cnxn : f.cnxns) {
            cnxn.setStale();
        }
        zk = null;

        resumeProcess.countDown();
        LOG.info("raise the latch");

        while (zks.getInflight() > 0) {
            Thread.sleep(50);
        }

        // the rest of the 3 requests will be dropped
        // but only the first one for a connection will be counted
        metrics = MetricsUtils.currentServerMetrics();
        assertEquals(2L, (long) metrics.get("prep_processor_request_queued"));
        assertEquals(1, (long) metrics.get("stale_requests_dropped"));
    }

}