一个内存泄漏问题的排查

红太狼 2023-06-16 07:46 9阅读 0赞

1.  监控的MEM一直居高不下：

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3RocXR6cQ_size_16_color_FFFFFF_t_70]

1.  使用jstat命令查看gc的情况，发现YGC已经停止，一直在FGC，怀疑内存已经泄漏，堆内存中有大量无法回收的对象。

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3RocXR6cQ_size_16_color_FFFFFF_t_70 1]

1.  然后查看gc日志，发现年轻代和老年代使用率达到99%，且Full GC后内存没有被回收。确定肯定是有对象无法被回收。  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3RocXR6cQ_size_16_color_FFFFFF_t_70 2]
2.  把堆的dump文件下载下来，用eclipse的mat插件分析error.hprof文件：  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3RocXR6cQ_size_16_color_FFFFFF_t_70 3]  
    发现有个对象占用内存特别大：BouncyCastleProvider();  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3RocXR6cQ_size_16_color_FFFFFF_t_70 4]  
    根据对象定位到项目代码，发现解密方法里用到了该对象：

/**
         * 需要解密的数据
         * 这是加解密的功能，每次运行加解密都会new一个BouncyCastleProvider对象,放倒Cipher.getInstance()方法中。
         * verificationResults.put(var0, PROVIDER_VERIFIED);
         * 导致内存被占用儿得不到了回收
         * @param data
         * @return
         * @throws Exception
         */
        public static String decrypt(String data) throws Exception {
            Cipher cipher = Cipher.getInstance("DES", new BouncyCastleProvider());
            return "a";
        }

依赖树已经提示了，往里面跟源码，发现verificationResults对象一直在put BouncyCastleProvider()对象，而没有remove，导致BouncyCastleProvider()对象越来越多，最后内存溢出。

final class JceSecurity {
       
        private static final Map<Provider, Object> verificationResults = new IdentityHashMap();
    	//省略。。。。
    static synchronized Exception getVerificationResult(Provider var0) {
            Object var1 = verificationResults.get(var0);
            if (var1 == PROVIDER_VERIFIED) {
                return null;
            } else if (var1 != null) {
                return (Exception)var1;
            } else if (verifyingProviders.get(var0) != null) {
                return new NoSuchProviderException("Recursion during verification");
            } else {
                Exception var3;
                try {
                    verifyingProviders.put(var0, Boolean.FALSE);
                    URL var2 = getCodeBase(var0.getClass());
                    verifyProviderJar(var2);
                    verificationResults.put(var0, PROVIDER_VERIFIED);
                    var3 = null;
                    return var3;
                } catch (Exception var7) {
                    verificationResults.put(var0, var7);
                    var3 = var7;
                } finally {
                    verifyingProviders.remove(var0);
                }
    
                return var3;
            }
        }
    }

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