線程池執行程序不更新並發哈希圖

Question

我使用線程池執行程序生成5個線程，以並行執行5個不同的命令。 在完成每個線程之后，我將使用threadid項作為鍵並以值終止的方式更新並發哈希圖。 但是我的線程池沒有更新成功執行命令的哈希表。

主類：

package com.cisco.executor;

import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

public class MainExecutor {

    static String element;
    static ConcurrentHashMap<Integer, String> map = new ConcurrentHashMap<Integer, String>();
    static Integer array[] = { 1, 2, 3, 4, 5 };
//  static Integer array[] = { 1 };
    static List<Integer> threadid = Arrays.asList(array);
    static String SQOOP_XXCCS_DS_SAHDR_CORE = ReadProperties.getInstance().getProperty("SQOOP_XXCCS_DS_SAHDR_CORE");
    static String SQOOP_XXCCS_DS_CVDPRDLINE_DETAIL = ReadProperties.getInstance()
            .getProperty("SQOOP_XXCCS_DS_CVDPRDLINE_DETAIL");
    static String SQOOP_XXCCS_DS_INSTANCE_DETAIL = ReadProperties.getInstance()
            .getProperty("SQOOP_XXCCS_DS_INSTANCE_DETAIL");
    static String SQOOP_XXCCS_SCDC_PRODUCT_PROFILE = ReadProperties.getInstance()
            .getProperty("SQOOP_XXCCS_SCDC_PRODUCT_PROFILE");
    static String SQOOP_MTL_SYSTEM_ITEMS_B = ReadProperties.getInstance().getProperty("SQOOP_MTL_SYSTEM_ITEMS_B");

    public static void main(String[] args) {

        ThreadPoolExecutor executors = (ThreadPoolExecutor) Executors.newFixedThreadPool(5);
//      ThreadPoolExecutor executors = (ThreadPoolExecutor) Executors.newFixedThreadPool(1);

        System.out.println("at executors step");
        List<String> getlist = getList();
        Iterator<Integer> itr2 = threadid.iterator();

        for (Iterator<String> itr = getlist.iterator(); itr.hasNext() && itr2.hasNext();) {
            String element = (String) itr.next();
            int thread_id = itr2.next();
            String[] command = { "ssh", "hddev-c01-edge-02", "\"" + element + "\"" };
            System.out.println("the command is as below ");
            System.out.println(Arrays.toString(command));
            System.out.println("inside the iterator");
            ParallelExecutor pe = new ParallelExecutor(command, thread_id, map);
            executors.execute(pe);
        }
        // executors.shutdown();
        for(Map.Entry<Integer, String> entry: map.entrySet())
        {
            Integer key = entry.getKey();
            String value = entry.getValue();            
            System.out.println("The key is " + key + " The value is " + value);
            System.out.println("Thread " + key + " is terminated");
        }

    }

    public static List<String> getList() {
        List<String> commandlist = new ArrayList<String>();
        System.out.println("inside getList");
        commandlist.add(SQOOP_XXCCS_DS_SAHDR_CORE);
        commandlist.add(SQOOP_XXCCS_DS_CVDPRDLINE_DETAIL);
        commandlist.add(SQOOP_XXCCS_DS_INSTANCE_DETAIL);
        commandlist.add(SQOOP_XXCCS_SCDC_PRODUCT_PROFILE);
        commandlist.add(SQOOP_MTL_SYSTEM_ITEMS_B);
        return commandlist;
    }

}

可運行類：

package com.cisco.executor;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.concurrent.ConcurrentHashMap;

import org.apache.log4j.Logger;

public class ParallelExecutor implements Runnable {

    private static Logger LOGGER = Logger.getLogger(ParallelExecutor.class);

    String[] command;
    int threadid;
    ConcurrentHashMap<Integer, String> map;

    public ParallelExecutor(String[] command, int threadid, ConcurrentHashMap<Integer, String> map) {
        this.command = command;
        this.threadid = threadid;
        this.map = map;
    }

    @Override
    public void run() {
        ProcessBuilder processbuilder = new ProcessBuilder(command);
        LOGGER.info(command);
        try {
            Process process = processbuilder.inheritIO().start();
            System.out.println("inside process builder ");
            process.waitFor();
            BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream()));
            String readline;
            while ((readline = reader.readLine()) != null) {
                LOGGER.info(readline);
            }
            // getting the thread state and adding it to a collection
            Thread.State state = Thread.currentThread().getState();
            if (state == Thread.State.TERMINATED) {
                map.put(threadid, "TERMINATED");
            }
        } catch (Exception e) {
            LOGGER.error(e.getMessage());
        }
    }

}

我的實現是錯誤的。 有人可以幫我實施。

Answer 1

我建議您保留Future對象並檢查它們，而不是嘗試捕獲線程中線程的結果（如果拋出異常/錯誤，則容易出錯）。

    ExecutorService exec = Executors.newFixedThreadPool(5);

    System.out.println("at executors step");
    Map<String, Future<?>> results = new HashMap<>();
    for (String element : getList()) {
        String[] command = { "ssh", "hddev-c01-edge-02", "\"" + element + "\"" };
        results.put(element, exec.submit(new ParallelExecutor(command, thread_id, map)));
    }
    for(Map.Entry<String, Future<?>> entry: map.entrySet()) {
        try {
            entry.getValue().get();
            System.out.println(entry.getKey()+ " is complete");
        } catch (ExecutionException e) {
            System.out.println(entry.getKey()+ " failed with");
            e.getCause().printStackTrace(System.out);
        }
    }

Answer 2

ThreadPoolExecutor直到被要求這樣做時才終止。 所以，首先你必須打電話

// executors.shutdown();

，您將其保留為已評論。 2，您需要等待線程正確終止。 為此，在for（Map.Entry entry：map.entrySet（））之前添加一個循環

while (!es.isTerminated()) {
        }

但是，由於一個線程可能會運行許多可運行對象，並且如果我正確理解了您的信息，那么一旦執行了一個可運行對象，您就想更新CHM。

為此，您必須使用CustomThread類。 擴展線程並僅覆蓋afterExecute()方法中的1個方法，您需要在其中放置代碼以使用Runnable的ID和終止狀態更新CHM。 但是請記住，這意味着完成傳遞的Runnables run（）方法，而不是基礎線程的終止。