Jps, jstat, jstack and jmap are commonly used tools to analyze problems encountered by tomcat when analyzing jvm in operation and maintenance.

The common problems of tomcat are:

  OOM, lock dead, lock contention, Java consumes too much CPU

  The above tools can be used for analysis.

Fast Entry of Common Analytical Methods in Production:

  # JPS --> View running java processes

  # jstat-gc process PID - > Check the memory usage of the process, the number and time of garbage collection in the younger generation and the older generation

  # jstat -gccause process PID - > View process garbage collection reasons

  # jmap -heap process PID - > View process heap memory usage

  # jstack-l process PID - > View Thread information for analysis of the situation of tomcat dummy death caused by deadlock

jps:java virtual machine process viewing tool

  jps [options] [hostid]

   - m: Output parameters of the incoming main method

   - l: Displays the complete class name of main

   -v: Displays the parameters specified for the jvm virtual machine

  Commonly used combinations:

   #jps -m -l

   #jps -m -l -v  

[gcct1@localhost bin]$ jps -m -l -v
5966 org.apache.catalina.startup.Bootstrap start -Djava.util.logging.config.file=/mnt/tomcat/conf/logging.properties -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djava.endorsed.dirs=/mnt/tomcat/endorsed -Dcatalina.base=/mnt/tomcat -Dcatalina.home=/mnt/tomcat -Djava.io.tmpdir=/mnt/tomcat/temp
7006 sun.tools.jps.Jps -m -l -v -Denv.class.path=.:/usr/java/jdk1.7.0_79/lib/dt.jar:/usr/java/jdk1.7.0_79/lib/tools.jar -Dapplication.home=/usr/java/jdk1.7.0_79 -Xms8m

Jstat: Monitoring of memory usage and garbage collection at runtime of JVM virtual machine

  Jstat - < option > pid:(< Options > is a necessary option)

   - options: See which options are available

   - gc: When using this option, add the java process number after it; example jstat -gc 27564 [1s] (which can also be displayed as many times as possible)

     S0C,S1C: Represents the capacity of the first and second survivors
     S0U,S1U: Represents the used capacity of the first and second survival areas
     EC,EU: Indicates the capacity and usage of the eden region
     OC,OU: Indicates the capacity and usage of the geriatric area.
     PC,PU: Represents the memory capacity and usage of the persistent generation
     YGC,YGT: Represents the number and time-consuming occurrence of the Cenozoic GC
     FGCT,FGCT: Represents the frequency and time-consuming occurrence of Full GC in the elderly
     GCT: Represents the total GC time-consuming

   -gccause:
    LGCC: Reasons for Last GC
    GCC: Reasons for Current GC

[gcct1@localhost bin]$ jstat -gc 5966
 S0C    S1C    S0U    S1U      EC       EU        OC         OU       PC     PU    YGC     YGCT    FGC    FGCT     GCT   
40960.0 36864.0  0.0   36850.3 253952.0 161159.5  109056.0   74574.4   53248.0 45852.6     19    1.672   3      2.193    3.865
[gcct1@localhost bin]$ jstat -gccause 5966
  S0     S1     E      O      P     YGC     YGCT    FGC    FGCT     GCT    LGCC                 GCC                 
  0.00  99.96  63.76  68.38  86.11     19    1.672     3    2.193    3.865 Allocation Failure   No GC

jmap: View heap memory usage, similar to jstat

  - heap: Detailed output heap memory usage
  - histo[:live]: Detailed display of the number of objects in the entire java heap memory, size statistics;
  - histo: Displays all object information
  - histo:live: Shows only surviving object information
  - h: Getting Help Information
   Example: jmap-heap 5966 - > View heap memory usage in detail

[gcct1@localhost bin]$ jmap -heap 5966
Attaching to process ID 5966, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 24.79-b02

using thread-local object allocation.
Parallel GC with 2 thread(s)

Heap Configuration:
   MinHeapFreeRatio = 0
   MaxHeapFreeRatio = 100
   MaxHeapSize      = 1019215872 (972.0MB)
   NewSize          = 1310720 (1.25MB)
   MaxNewSize       = 17592186044415 MB
   OldSize          = 5439488 (5.1875MB)
   NewRatio         = 2
   SurvivorRatio    = 8
   PermSize         = 21757952 (20.75MB)
   MaxPermSize      = 85983232 (82.0MB)
   G1HeapRegionSize = 0 (0.0MB)
......

jstack: View thread stack information in a java process

  jstack [options] pid
  - l: long listings (which output complete lock information); jstack -l process number
  -m: Hybrid mode, which outputs java stack and C/C++ stack information

  Thread contention, thread deadlock and other information can be viewed through jstack