Catalog

Virtual machine performance monitoring 、 Fault handling

One 、 Virtual machine related commands

1、jps： Virtual machine process health tool

2、jstat： Virtual machine statistics monitoring tool

3、jinfo：Java Configuration information tools

4、jmap：Java Memory imaging tools

5、jhat： Virtual machine heap dump snapshot analysis tool

6、jstack：Java Stack trace tool

Two 、 Visual fault handling tool

1、JConsole：Java Monitoring and management console

2、VisualVM： Fault handling collection tools

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Virtual machine performance monitoring 、 Fault handling

 

One 、 Virtual machine related commands

1、jps： Virtual machine process health tool

Function and Linux Medium ps Command similar , Available lists the running virtual machine processes , And the only of the process ID
Command format ：jps [options] [hostid]

Example ：

 

2、jstat： Virtual machine statistics monitoring tool

It is a command tool used to monitor the running status information of virtual machines . Exhibition Java Class loading in process 、 Memory 、 garbage collection 、 Run time data such as instant compilation .
Command format ：
jstat [option pid [interval[s|ms]] [count]] 
jstat [- Command options ] [pid] [ Time interval between / millisecond ] [ Query times ]

Common options ：
-class: Monitoring class loading 、 Unloading quantity 、 Total space and time spent loading classes
-gc: monitor Java Pile condition , Include Eden District ,2 individual Survivor District , Old age , Permanent equivalent capacity , used space , Total garbage collection time, etc
-gcutil: Monitoring content and -gc Basically the same , Single output mainly focuses on Java The maximum and minimum space used by each area of the heap

Parameters, ：
S0C： The first of the young generation survivor（ Survival zone ） The capacity of （ byte ）
S1C： The second of the younger generation survivor（ Survival zone ） The capacity of ( byte )
S0U ： The first of the young generation survivor（ Survival zone ） Space has been used ( byte )
S1U ： The second of the younger generation survivor（ Survival zone ） Space has been used ( byte )
EC ： Young generation Eden（ The garden of Eden ） The capacity of ( byte )
EU ： Young generation Eden（ The garden of Eden ） Space has been used ( byte )
OC ：Old Generation capacity ( byte )
OU ：Old Generation has used space at present ( byte )
MC：metaspace( Meta space ) The capacity of ( byte )
MU：metaspace( Meta space ) Space has been used ( byte )
YGC ： From application startup to sampling in the younger generation gc frequency
YGCT ： From application startup to sampling in the younger generation gc Time spent (s)
FGC ： From application startup to sampling old generation ( whole gc)gc frequency
FGCT ： From application startup to sampling old generation ( whole gc)gc Time spent (s)
GCT： From application startup to sampling gc The total time spent (s)

Example ：

Printing process id yes 6132 Information about , Every time 1000ms Print once , Print 10 Time .

3、jinfo：Java Configuration information tools

It is to view and call various parameters of the virtual machine in real time .
Command format ：
jinfo [option] pid

Example ：

I am here JpsTest The program added -XX:CMSInitiatingOccupancyFraction=85 Launch parameters

4、jmap：Java Memory imaging tools

Used to generate a heap dump snapshot （dump file ）. If not jmap command , It can also be done through -XX:+HeapDumpOnOutMemoryError Parameter to enable the virtual machine to automatically generate a heap dump snapshot file after the memory overflow exception occurs .
Command format ：jmap [option] pid

Common options ：
-dump： Generate Java Heap dump snapshot . The format is -dump:[live,]format=b,file=<filename>, among live The sub parameter indicates whether only dump Out of the living . example ：jmap -dump:format=b,file=dumpFile.bin <pid>
-heap： Show Java Heap details . notes ： Only in linux、Solaris Effective under platform .
-histo： Show statistics for objects in the heap , Including class 、 Number of instances 、 Aggregate capacity

Example ：

5、jhat： Virtual machine heap dump snapshot analysis tool

And jamp Use it with , It's used to analyze jmap Generated heap dump snapshot .jhat Built in a small server , After generating the analysis results of the heap dump snapshot , It can be viewed directly in the browser .
Command format ：jhat <filename>
Screen display "Server is ready." Then enter... In the browser ,http://localhost:7000/ You can see the analysis results .
notes ： There is one saying. , The result is not very intuitive . I usually use more jamp Medium -histo, It looks more intuitive .

Example ：

6、jstack：Java Stack trace tool

Used to generate the current Java Thread snapshot of the current time of the process . Thread snapshot is a collection of method stacks being executed by all threads in the current virtual machine . It is often used to check thread deadlock , Dead cycle , Thread blocking for a long time .
Command format ：
jstack [option] pid

Common options ：
-l： In addition to stack information , Additional information about the lock is also displayed . You can also output to the corresponding file , example ：jstack -l <pid> > stack.log
-F： When the normal output request is not reflected , This option can force the output of thread stack information .

Because of me linux The server is not running Java Program , So the examples are all in window Upper .
In addition to some of the above , There are many other tools .
Such as ：jar（ Create and manage jar file ）,java（Java Run the tool ）,javac（Java compiler ）,javap（ Bytecode analysis tool ） wait .
Interested partners can have an in-depth understanding of a wave of , By the way, share a wave with me .

Example ：

stack.log In file , Related thread information can also be printed

 

Two 、 Visual fault handling tool

1、JConsole：Java Monitoring and management console

Is based on JMX Visual monitoring of 、 Management tools . The main function is through JMX Of MBean Collect information and adjust parameters dynamically .
The tool is installed before we jdk Of bin Under the table of contents , You can see that there is a jconsole.exe file .
Open the tool , When we have Java Program runtime , He will automatically detect this machine Java process , Then we choose the corresponding process , You can enter the visual interface to view the corresponding information .
Mainly memory 、 Threads 、 Number of class loads 、VM Summary 、MBean A few chunks of information . If you are interested, you can run one on your computer Java Program , Then order a little by yourself , Have a look .
Memory monitoring ： Equivalent to what we introduced before jstat The command is visualized . Used to monitor the change trend of virtual machine memory managed by the collector .
Thread monitoring ： Equivalent to what we introduced before jstack The command is visualized . For monitoring Java Process thread running status . It's also very considerate to have a special button to detect deadlock .

2、VisualVM： Fault handling collection tools

It is one of the powerful operation monitoring and fault handling programs . In addition to regular operation monitoring 、 Troubleshooting , There are also tools such as performance analysis .
function ：
 1) Show Java Process and related configuration environment information of the process , amount to jps,jinfo.
 2) Monitor the application's processor , garbage collection , Pile up , Thread and other information , amount to jstas,jstack
 3)dump And analyze heap dump snapshot , amount to jmap,jhat
 4) Analysis of program performance
 5) You can install plug-ins , More functions can be expanded

  Offline official plug-in address ：https://visualvm.github.io/pluginscenters.html
  On-line java visualvm Installing a plug-in . Pictured ：

stay Profiler Page , You can view method level processor execution time analysis and memory analysis during runtime .

Btrace Dynamic log tracking , This is a VisualVM Plug in for , It's very powerful . You can do this without interrupting the target program , adopt HotSpot The virtual machine allows you to follow the code function of newly loaded classes without downtime , Dynamically add debugging code that does not exist .
When the program has abnormal problems , You can use this plug-in , To add some debugging log code , And it's different to stop the service .

JMC(Java Mission Control)： Sustainable online monitoring tools

Used for remote monitoring and management JVM The virtual machine .
You need to add the following parameters when the service process at the remote end starts ：
-Dcom.sun.management.jmxremote.port=9999 
-Dcom.sun.management.jmxremote.ssl=false 
-Dcom.sun.management.jmxremote.authenticate=false 
-Djava.rmi.server.hostname=192.168.31.31

-XX:+UnlockCommercialFeatures -XX:+FlightRecorder

And then in VisualVM In the tools , choice " file "->" Add remote host ", Fill in the address and port we configured, and connect to the interface . Subsequent operations are consistent locally .

 

In our usual development process ,Linux Servers are used more , Therefore, compared with the visual interface , Personally, I think the relevant virtual machine commands should be used more .