Java memory monitoring method

1, JMX function

1.1 Introduction

JMX (Java Management Extensions, the Java Management Extensions) is an application program, devices, systems and other implants framework management functions. JMX across a range of heterogeneous operating system platform, system architecture and network transport protocols , flexible development seamlessly integrated system, network and service management applications.

The so-called JMX, is an acronym for Java Management Extensions (Java Management Extensions) is a framework for implant management functions for the application. Users can use these agents and service management to achieve in any Java application.

JMX architecture diagram:

 

Three-tier structure

1, the base layer: mainly Mbean, managed java bean They are divided into the following four Mbean Types of description standard MBean This type of MBean simplest, it can manage the resources (including properties, methods, time) must be defined in the interface, and then MBean must implement this interface. Its name must also follow certain specifications, such as our MBean Hello, the interface must be HelloMBean. dynamic MBean Javax.management.DynamicMBean must implement the interface, all of the properties, methods are defined at run time model MBean Compared with standard and dynamic MBean, you can not write MBean class, you can simply use javax.management.modelmbean.RequiredModelMBean. RequiredModelMBean realized ModelMBean interface, and expanded ModelMBean DynamicMBean interface, similar to DynamicMBean, Model MBean management resources are defined at run time. The difference is that with DynamicMBean, resource management DynamicMBean general definition (decision to manage those resources when running) in DynamicMBean, whereas model MBean management of resources is not in the MBean, but on the outside (usually a class), only running only when set by the method of adding it to the model MBean. 2, adaptation layer: MbeanServer, provide registration and management of resources 3, the access layer: providing remote access to an inlet

The most common scenario is JMX basic information and monitor the operation of Java programs, a Java program can open any JMX, and then use JConsole or Visual VM preview.

Adding JMX 1.2 features

 1, wrapper program to add JMX functionality.

Add the following configuration wrapper.conf configuration file:

local.jmx.port=39900 wrapper.java.additional.2=-Djava.rmi.server.hostname=192.168.1.75 wrapper.java.additional.3=-Dcom.sun.management.jmxremote.port=39900 wrapper.java.additional.4=-Dcom.sun.management.jmxremote.ssl=false wrapper.java.additional.5=-Dcom.sun.management.jmxremote.authenticate=false

 2, the general procedure to add JMX java function.

    Specify the following instruction after the program command java

-Djava.rmi.server.hostname=127.0.0.1 -Dcom.sun.management.jmxremote.port=1000 -Dcom.sun.management.jmxremote.ssl=false -Dcom.sun.management.jmxremote.authenticate=false

 

3, tomcat JMX add functionality.

 

CATALINA_OPTS="-Dcom.sun.management.jmxremote -Djava.rmi.server.hostname=ip -Dcom.sun.management.jmxremote.port=9999 -Dcom.sun.management.jmxremote.ssl=false -Dcom.sun.management.jmxremote.authenticate=false"

 

 

2, Jconsole, jvisualvm tools

2.1 jconsole tool

1, the remote connection process

 

2, the connection is successful may be observed overview, memory, threads, classes, the VM summary, the MBean

 

3, you can view a different area of ​​memory usage

 

2.2 jvisualvm tools

1, the remote connection process

 

2, you can see an overview of successful login, monitoring, thread, sampler.

 

3, monitors: CPU, memory, class, thread

 

 

4, memory mirroring can be done by decimator

 

 

 

Check the resulting file on a remote server:

 

 

 

3, file parsing heap

3.1, use the command parsing jhat

jhat -J-mx10240m heapdump-1563861495449.hprof

   

   The following message appears, indicating that the image file is read successfully

 

3.2, page display

Input UI using the following address: http://192.168.1.75:7000/

 

 

 

 

You can view the page by:

(1) shows all classes included in the stack

(2) from the root set references to an object can be

(3) shows the number of instances of all classes of platforms including

Distribution Table (4) Examples of the stack

(5) perform object query

 

 

 

4, JVM tuning monitoring tools

jps、jstack、jmap、jhat、jstat、hprof

jmap这个命令执行，JVM会将整个heap的信息dump写入到一个文件，heap如果比较大的话，就会导致这个过程比较耗时，并且执行的过程中为了保证dump的信息是可靠的，所以会暂停应用， 线上系统慎用。