was宕機(jī)常見問題及參考解決方案-展示頁
2025-06-14 19:42本頁面
【正文】 具：(IBM Support Assistant)Memory Dump Diagnostic for Java (MDD4J)應(yīng)對策略：調(diào)整垃圾回收策略，或者改變算法，調(diào)整程序，把很多局部變量（小對象）全局化。頻繁垃圾回收（Frequent GC）多次循環(huán)，去申請很多的小對象。In this case, a thread acquires the lock on lock1, At the same time, another thread acquires the lock on lock2. so the threads are deadlocked: neither thread will give up its lock until it acquires the other lock, but neither will be able to acquire the other lock until the other thread gives it up. One of the best ways to prevent the potential for deadlock is to avoid acquiring more than one lock at a time, which is often practical. However, if that is not possible, you need a strategy that ensures you acquire multiple locks in a consistent, defined order. 應(yīng)對策略：申請資源鎖，按順序申請，或者一次性全部申請。這就形成了資源循環(huán)申請的一個死鎖。比如設(shè)置多個鎖或者提高同步代碼塊的執(zhí)行效率。同步過度（Excessive Synchronization）LIS系統(tǒng)FORMULA ONE報表打印就是采用了SYNCHRONIZE思想，如果有某一個大的報表長時間打不出來的話，會導(dǎo)致其它所有的報表打印線程全部掛起。這樣導(dǎo)致的等待泄漏，從而線程掛起。WAS宕機(jī)問題總結(jié)起來有以下幾類：一、線程掛起導(dǎo)致線程池滿（Thread Hang）:Hangs refer to the JVM locking up or refusing to respond.A hang can occur when:1）Your application entered an wait leak2）Excessive Synchronization cause performance problems3）A deadlock has occurred收集日志：生成JAVA CORE分析工具：IBM Thread and Monitor Dump Analyzer線程等待泄漏(Wait Leaks)常見的情況就是，有很多線程使用wait()方法，等待被喚醒notify（）。但是，存在某一個線程獲取到鎖并且進(jìn)行業(yè)務(wù)處理完成后，忘記去喚醒等待執(zhí)行的進(jìn)程。When you use the wait/notify mechanism, you typically have one or more threads blocked in the wait() call, waiting to be notified. The notifying thread is supposed to call notify() or notifyAll() to signal that waiting threads can wake up and carry on processing.A problmatic situation could occur that the notify() call is invoked before the threads go into the wait() method. In this case, the waiting threads would not be notified anymore and bee stuck. So, do not forget to notify the waiting theads in you application and maks sure that the Notify action is performed after all the waiting threads
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