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This article mainly shows you "what are the tips for Java performance monitoring", which is easy to understand and organized. I hope it can help you solve your doubts. Let me lead you to study and learn this article "what are the tips for Java performance monitoring?"

1. Remote connection process

Because the Web application analysis tool assumes connectivity analysis through a socket, you only need to do a little configuration to set up JConsole (or JVMTI-based profilers, for that matter) to monitor / analyze remotely running applications.

If Tomcat is running on a machine called "webserve" and JVM has started JMX and listens on port 9004, connecting to it from JConsole (or any JMX client) requires a JMX URL "service:jmx:rmi:///jndi/rmi://webserver:9004/jmxrmi".

Basically, to analyze an application server running in a remote data center, all you need is a JMX URL.

2.JDK comes with an analyzer

Many developers do not realize that a parser is included in JDK since Java 5. JConsole (or Java platform * version, VisualVM) is a built-in parser that is as easy to start as the Java compiler. If you are starting from the command line, make JDK on PATH and run jconsole. If you start from GUIshell, find the JDK installation path, open the bin folder, and double-click jconsole.

When the analysis tool pops up (depending on the version of Java running and the number of Java programs running), a dialog box may appear asking for the URL of a process to connect, or it may list many different local Java processes (sometimes including the JConsole process itself) to connect.

Use JConsole for work

In Java 5, the Java process is not set to parse by default, but through a command line parameter-Dcom.sun.management.jmxremote-- tells Java 5 VM to open the connection at startup so that the parser can find them; when the process is picked up by JConsole, you can only double-click it to start the analysis.

Parsers have their own overhead, so the way to * is to take some time to figure out what the overhead is. The easiest way to find JConsole overhead is to first run an application alone, then run it under an analyzer, and measure the difference. Applications cannot be too large or too small; I like to use the SwingSet2 samples that come with JDK best. So I use-verbose:gc to try to run SwingSet2 to see garbage collection cleanup, then run the same application and connect the JConsole parser to it. When the JConsole is connected, a stable GC cleanup flow appears, otherwise it will not occur. This is the performance overhead of the parser.

JConsole or VisualVM?

JConsole has been released with the Java platform version since Java 5, while VisualVM is an upgraded parser based on NetBeans, released * times in update 12 of Java 6. Most of them have not been updated to Java 6, so this article focuses on JConsole. However, most techniques are related to both parsers.

3. Tracking statistics

JConsole has a number of tabs useful for collecting statistics, including:

Memory: tracks activity for each heap in the JVM garbage collector.

Threads: check the current thread activity in the target JVM.

Classes: observe the total number of loaded classes in VM.

These tabs (and associated charts) are provided by each JMX object registered on the JMX server by each Java 5 and later VM, and are built into JVM. A complete list of bean available in a given JVM is listed on the MBeans tab, including some metadata and a limited user interface to view data or perform operations. (however, registration notifications are outside the JConsole user interface. )

Use statistics

Suppose a Tomcat process dies of OutOfMemoryError. If you want to figure out what's going on, open JConsole, click the Classes tab, and check the class count once in a while. If the number rises steadily, you can assume that there is a ClassLoader vulnerability somewhere in your application server or your code that will soon run out of PermGen space. If you need further confirmation of the problem, see the Memory tab.

Don't be typical.

Common responses to performance problems in application code are found to be varied, but also predictable. Early Java programmers may be angry with the old IDE and begin code reviews of major parts of the code base, looking for familiar "red flags" in the source code, such as asynchronous blocks, object quotas, and so on. As programming experience increases, developers may take a closer look at the-X flag supported by JVM to find ways to optimize the garbage collector. Of course, for beginners, go directly to Google in the hope that someone else will discover JVM's magical "make it go fast" transformation and avoid rewriting the code.

In essence, there is nothing wrong with these methods, but they are all risky. The most effective response to a performance problem is to use a parser-- now that they are built into the Java platform, there is really no reason not to do so!

4.JConsole is not unfathomable

As a parser utility, JConsole is excellent, but there are better tools. Some analysis plug-ins come with profilers or smart user interfaces that track more data by default than JConsole.

The real attraction of JConsole is that the entire program is written in "plain old Java", which means that any Java developer can write such a utility. In fact, JDK even includes examples of how to customize JConsole by creating a plug-in. VisualVM, built on top of NetBeans, further extends the concept of plug-ins.

If JConsole (or VisualVM, or any other tool) doesn't meet your needs, or you can't track what you want to track, or if you can't track it your way, you can write your own tool. If you find Java code troublesome, Groovy or JRuby or many other JVM languages can help you finish faster.

What you really need is a fast, rough (quick-and-dirty) command-line tool connected by JVM that can track exactly the data you are interested in in the way you want.

5. Create a heap dump for offline analysis

Everything is going on quickly in a production environment, and you may not have time to spend on your application profiler; instead, you can save a snapshot of each event in the Java environment and then look at it. You can do the same in JConsole, and even better in VisualVM.

First find the MBeans tab and open the com.sun.management node, followed by the HotSpotDiagnostic node. Now, select Operations and notice the "dumpHeap" button in the right panel. If you pass a file name to dumpHeap to dump in * ("string") input boxes, it will heap a snapshot of the entire JVM and dump it to that file.

Later, you can use a variety of different business parsers to analyze files, or you can use VisualVM to analyze snapshots. Remember, VisualVM is available in Java 6 and is downloaded separately. )

These are all the contents of the article "what are the Tips for Java performance Monitoring?" Thank you for reading! I believe we all have a certain understanding, hope to share the content to help you, if you want to learn more knowledge, welcome to follow the industry information channel!

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