Translator's note: the desire to translate the note appeared early on a June morning after reading it half asleep in a subway car. Target audience: people who are taking their first steps in the world of Java and, due to the nature of their basic technical background or desire, are very eager to get under the hood of Java and learn all the “electrodynamic” processes. I am sure that for those who read this, this will be the starting point for a journey into the world of configuring the JVM and GC. Fair wind! Original article here As a developer, you spend countless hours cleaning out bugs from a Java application and getting performance where it needs to be. During testing, you notice that the application gradually runs slower, and in the end it completely crashes or simply shows poor performance. Eventually accept that memory leaks occur. Garbage collector Java does its best to deal with these leaks. But there are only so many things that can be done when faced with situations like these. You need ways to identify memory leak calls, identify causes, and understand the role of the Java garbage collector in affecting overall application performance.
Main Symptoms of Java Memory Leaks
There are several symptoms that indicate that an application has memory leak problems. A slight decrease in performance, rather than a sudden application failure, only indicates a memory leak. The problem can happen every time during operation or only when the application starts working with a large amount of data or, on the contrary, you start scaling the application. The application will probably show an out of memory error once the leak has consumed all available memory resources. If you restart the application and hope for the best, you will encounter repeated crashes until the leak is fixed. In general, memory leaks happen when object references accumulate instead of freeing memory. They occupy all available memory and make it impossible for the application to access the resources it needs.
Configuration errors appearing as memory leaks
Before you look into situations that cause Java memory problems and conduct an analysis, you need to make sure that the research is not related to a completely different problem. Some out-of-memory errors occur due to various errors, such as configuration errors. The application may be low on heap memory or may be conflicting with other applications on the system. If you start talking about low memory issues but can't figure out what's causing the leak, take a different look at the application. You will find that you need to make changes to the finalization thread or increase the amount of permanent generation space, which is an area of JVM memory for storing descriptions of Java classes and some additional data.
Benefits of Memory Monitoring Tools
Memory monitoring tools provide greater visibility into a Java application's use of available resources. By using this software, you take a step towards narrowing down the search for the root of the problem of memory leaks and other performance incidents. The tools come in several categories, and you may need to use a variety of applications to figure out how to properly flag the problem and what went wrong, even if you're dealing with memory leaks. Heap dump files provide the necessary information for analyzing Java memory. In this case, you need to use two tools: one to generate a dump file and another for detailed analysis. This solution provides detailed information about what is happening with the application. Once the tool pinpoints the locations of possible problems and works to narrow down the area to discover the exact location of the incident. And this period of time is the time of the longest and most depressing part of trial and error. The memory analyzer indicates several problems in your code, but you are not absolutely sure what problems your application is encountering. If you still encounter the same error, start over and work on another possible error. Make one change at a time and try to duplicate the error. You will need to let the application run for some time to duplicate the error conditions. If there is a memory leak during the first test, be sure to load test the application. An application may work fine with a small amount of data, but may again throw the same errors when working with a large amount of data. If the same error still occurs, you need to start over and look for another possible cause. Memory monitoring tools prove their usefulness once the application is fully operational. You can remotely monitor JVM performance and proactively detect failure situations before a developer dives into the problem and collects historical performance data to help improve their programming techniques in the future and see how Java performs under heavy load. Many solutions include "danger" alert modes or other similar modes so that the developer can immediately know what is going wrong. Every developer does not want a critical application, while in production, to crash and cause the loss of tens or hundreds of thousands of dollars during application downtime, so memory monitoring tools reduce the developer's response time. Memory monitoring applications allow you to start the diagnostic process instantly, instead of asking you to go to the customer, where no one will tell you exactly what error happened or what error code the application generated. If you often find yourself immersed in memory and performance problems of your Java application, take a deep dive into the testing process. Identify each weak area in the development process and change your testing strategies. Consult with colleagues and compare your testing approaches with existing best practices. Sometimes you need to revise a small piece of code and then ensure a lasting impact on the entire application.
Role of Garbage Collector on Java Memory and Memory Leaks
Garbage Collector in Java plays a key role in application performance and memory usage. It looks for unused (dead) objects and deletes them. These objects no longer occupy memory, so your application continues to ensure resource availability. Sometimes the application doesn't give the GC enough time or resources to remove dead objects and they accumulate. You may encounter a situation where there is active access to objects that you believe are dead. The garbage collector can't do anything about this because... its automated memory management mechanism bypasses active objects. Typically the garbage collector operates autonomously, but you need to tune its behavior to respond to severe memory problems. However, GC itself can cause performance problems.
GC areas
The garbage collector separates objects into different areas to optimize assembly. Young Generation features objects that die out quickly. The garbage collector often works in this area from the time he has to clean up. Objects that remain alive after reaching a certain period are transferred to Old Generation. In the Old Generation area, objects remain for a long time and are not removed by the collector as often. However, when the collector is running in the scope, the application goes through a large operation where the collector looks through live objects to clean up garbage. As a result, application objects are located in the final permanent generation area. Typically, these objects include the necessary JVM metadata. The application does not generate much garbage in Permanent Generation, but does need a collector to remove classes when the classes are no longer needed.
Relationship between Garbage Collector and response time
The garbage collector, regardless of the execution priority of application threads, stops them without waiting for completion. This phenomenon is called a "Stop the World" event. The Young Generation region of the garbage collector has a minor impact on performance, but problems are noticeable if the GC is doing intensive cleanup. You end up in a situation where the Young Generation minor GC is constantly running or the Old Generation goes into an uncontrolled state. In such a situation, you need to balance the Young Generation frequency with the performance that requires increasing the size of this collector area. The Permanent Generation and Old Generation regions of the garbage collector have a significant impact on application performance and memory usage. This major garbage cleanup operation goes through the heap to push out dead objects. The process takes longer than a minor build and the performance impact may take longer. When the scrubbing intensity is high and the Old Generation area size is large, the performance of the entire application is bogged down due to "Stop the world" events. Optimizing garbage collection requires monitoring how often a program is run, the impact on overall performance, and how to adjust application settings to reduce the frequency of monitoring. You may need to identify the same object placed more than once without the application having to fence itself off from the placement, or you may need to find the compression points that are holding the entire system back. Getting the balance right requires paying close attention to everything from CPU load to your garbage collector cycles, especially if Young and Old Generation are unbalanced. Addressing memory leaks and optimizing garbage collection helps improve the performance of a Java application. You are literally juggling a lot of moving parts. But with the right troubleshooting approach and analysis tools designed to provide rigorous visibility, you will reach the light at the end of the tunnel. Otherwise, you will suffer from performance-related problems. Careful memory placement and monitoring play a critical role in a Java application. You need to take full control of the interaction between garbage collection, object disposal, and performance to optimize your application and avoid out-of-memory errors. Monitoring tools help you stay on top of potential problems and highlight memory utilization trends so that you take a proactive approach to troubleshooting. Memory leaks often show the ineffectiveness of troubleshooting the usual way, especially if you encounter incorrect configuration parameter values, but solving memory-related issues can help you quickly avoid incidents that stand in your way. The perfection of Java memory tuning and GC makes your development process much easier.
GO TO FULL VERSION