Tools and commands that may be useful for Java troubleshooting

Tools and commands that may be useful for Java troubleshooting

――I put it together for myself

• https://qiita.com/YN0314/items/5e5c57d52ac1379daf6d
• https://qiita.com/i_matsui/items/4997ebedbdd7a6495509
• https://qiita.com/i_matsui/items/aabbdaa169c6ae51ecb3
• https://qiita.com/i_matsui/items/0d1ae2c7e9d17b6c04e0 -↑ I saw it with reference to the article

Java process list (jps)

You can see the process list of java

$JAVA_HOME/bin/jps

# -See more details in v. Options passed at startup, etc.

97312 RemoteMavenServer
97399 WSSampleMain
97398 Launcher
97403 Jps
81229 sbt-launch.jar
97005
97324 NailgunRunner

Stack trace (Thread dump) (jstack)

$JAVA_HOME/bin/jstack $Process number

# -You can get it even in the process that hangs in F

heap dump(jmap) Can be taken with the jmap command

$JAVA_HOME/bin/jmap -histo $Process number
#What and how many objects are in memory? What is the size? Get out

$JAVA_HOME/bin/jmap -heap $Process number
#You can see the situation of heap

• Java application stops while getting heapdump *

jcmd

The guy who put it together

https://www.ibm.com/developerworks/jp/java/library/j-5things8.html

Convenient tool

JMC ――You can see the stack, heap, etc. in GUI.

jvm-mon --Graphical view of CPU usage, processes, Threads and heap specifications on the terminal

Java option

When the JVM crashes in OOM, heap dump is issued without permission

java -XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=$Discharge destination directory

Drop the GC log

How to read the log

--When you say GC, other than Full GC --Full GC is as its name suggests --~~ K-> ~~ K is the amount of memory used before and after

Output to standard output

java -verbose:gc

Issued to a file

java -Xloggc:./gclog/gc.log

option

• Times of Day
  • -XX:+PrintGCDateStamps --Details
  • -XX:+PrintGCDetails --Log rotation
  • -XX:+UseGCLogFileRotation
  • -XX:GCLogFileSize=N --If N is 1K, 1M, 1G, you can set the rotation threshold of the log file.
  • -XX:NumberOfGCLogFiles=N --N Log files are rotated as 0, 1, 2 ... for the number of files --When output up to N, it is overwritten from 0