如何在我的Java应用程序中查找内存泄漏

这是我先前的问题HERE的后续问题.我目睹Java应用程序中的内存泄漏.最初,我以为泄漏来自应用程序的服务器组件.但是按照其他人的建议,事实并非如此.

我使用了一个工具来转储堆内存并使用JProfiler对其进行可视化.显然这是由于我怀疑有HashMaps.但是我不确定,因为我不熟悉如何解释转储.

这是我的应用程序结构的简短摘要(它每15分钟缓存一些文本数据以快速检索服务器线程).

是什么引起泄漏问题？以及如何从下面的转储中识别它？
显然我做new Object()和HashMap.put()的方式有一些泄漏问题吗？

初级入门班/主要.在这里,我启动了7个主要的HashMap,每个映射一个键(现在只有一个,最终将有16个键)映射到大约4000个单线JSON字符串的时间序列NavigableMap.

public class MyCache {
        static HashMap <String, NavigableMap <Long, String>> map1= new HashMap <String, NavigableMap <Long, String>> ();
        static HashMap <String, NavigableMap <Long, String>> map2= new HashMap <String, NavigableMap <Long, String>> ();
        static HashMap <String, NavigableMap <Long, String>> map3= new HashMap <String, NavigableMap <Long, String>> ();
        static HashMap <String, NavigableMap <Long, String>> map4= new HashMap <String, NavigableMap <Long, String>> ();
        static HashMap <String, NavigableMap <Long, String>> map5= new HashMap <String, NavigableMap <Long, String>> ();
        static HashMap <String, NavigableMap <Long, String>> map6= new HashMap <String, NavigableMap <Long, String>> ();
        static HashMap <String, NavigableMap <Long, String>> map7= new HashMap <String, NavigableMap <Long, String>> ();

        public static void main(String[] args) throws Exception {
    new Server();
    new Aggregation();
    }
}

然后在Aggregation()中,我从HTTP资源中获取一些文本,将其转换为JSON字符串,并将其缓存在一些临时的NavigableMaps中,然后将其放入主HashMap中(因此刷新不会对服务器造成太大影响).

public class Aggregation {
    static NavigableMap <Long, String> map1Temp= new ConcurrentSkipListMap <Long, String> ();;
    static NavigableMap <Long, String> map2Temp = new ConcurrentSkipListMap <Long, String> ();
    static NavigableMap <Long, String> map3Temp= new ConcurrentSkipListMap <Long, String> ();
    static NavigableMap <Long, String> map4Temp= new ConcurrentSkipListMap <Long, String> ();
    static NavigableMap <Long, String> map5Temp = new ConcurrentSkipListMap <Long, String> ();
    static NavigableMap <Long, String> map6Temp = new ConcurrentSkipListMap <Long, String> ();
    static NavigableMap <Long, String> map7Temp = new ConcurrentSkipListMap <Long, String> ();

public Aggregation(){

// loop to cache last 15 mins
while (true) {
            logger.info("START REFRESHING ...");
    for (int i = 0; i < mylist.size(); i++) {
        long startepoch = getTime(mylist.get(i).time);
        MyItem m = mylist.get(i);
        String index=(i+1)+"";

        process1(index, m.name, startepoch);
        //adds to map1Temp
        process2(index, m.name, startepoch);
        //adds to map2Temp
        process3(index, m.name, startepoch);
        //adds to map3Temp
        process4(index, m.name, startepoch);
        //adds to map4Temp
        process5(index, m.name, startepoch);
        //adds to map5Temp
        process6(index, m.name, startepoch);
        //adds to map6Temp
        process7(index, m.name, startepoch);
        //adds to map7Temp
        }

    //then `put` them in the main `HashMap` all at-once:
            MyCache.map1.put(channel, new ConcurrentSkipListMap <Long, String> (map1Temp));
            MyCache.map2.put(channel, new ConcurrentSkipListMap <Long, String> (map2Temp));
            MyCache.map3.put(channel, new ConcurrentSkipListMap <Long, String>(map3Temp));
            MyCache.map4.put(channel, new ConcurrentSkipListMap <Long, String>(map4Temp));
            MyCache.map5.put(channel, new ConcurrentSkipListMap <Long, String> (map5Temp));
            MyCache.map6.put(channel, new ConcurrentSkipListMap <Long, String> (map6Temp));
            MyCache.map7.put(channel, new ConcurrentSkipListMap <Long, String> (map7Temp));

//printing the size of all Hashmap entries. They don't grow :-/
logger.info("\t"+"map1.size(): "+MyCache.map1.get(key).size());
logger.info("\t"+"map2.size(): "+MyCache.map2.get(key).size());
//and other 5...        

//then clear the temp maps so they don't grow over and over
            map1Temp.clear();
            map2Temp.clear();
            map3Temp.clear();
            map4Temp.clear();
            map5Temp.clear();
            map6Temp.clear();
            map7Temp.clear();
    }
//sleep for 15 min until next caching cycle
Thread.sleep(cacheEvery*1000*60);
}

解决方法:

内存分析器告诉您,您有3个庞大的HashMap数据结构,它们占用约8GB的RAM …包括它们引用的闭包键和值对象.看起来它们可能是地图.

那可能是您的内存泄漏的证据.您的应用程序正在向地图数据结构中添加越来越多的条目,并且(大概)没有删除它们.那是内存泄漏的一种形式.

(请注意,这是您在上一个问题中未向我们显示的代码的一部分…)

标签：heap-memory,memory-leaks,jhat,jprofiler,java
来源： https://codeday.me/bug/20191108/2005969.html