Swiss Java Knife (SJK)

SJK is a command line tool for JVM diagnostic, troubleshooting and profiling.

SJK exploits standard diagnostic interfaces of JVM (such as JMX, JVM attach and perf counters) and add some more logic on top to be useful for common troubleshooting case. SJK is also can be used as library for building application specific diagnostic tools or to enhance your code with self monitoring features.

What you can do with SJK?

Monitor Java threads in real time
Analyze head dynamics with advanced class histograms
Access MBean attributes and operation from command line
Create flame graphs and over reports from snapshots created VisualVM, Java Flight Recorder or SJK's own sampler

See full command reference.

Download

Latest prebuild binaries

wget https://bit.ly/2YNDZfg -O sjk.jar -> sjk.jar - all commands without mxdump
wget https://bit.ly/2H3Uqck -O sjk.jar -> sjk-plus.jar - all commands

Starting sjk

java -jar sjk.jar <cmd> <arguments>
java -jar sjk.jar --commands
java -jar sjk.jar --help <cmd>

Below a few command from SJK (full command reference).

ttop

Pools thread CPU usage of target JVM and periodically report to console.

can attach via PID or open JMX port
display thread memory allocation rate and cumulative process allocation rate
display safe point time consumption (only if attache via PID)

More details

hh

Similar to jmap -histo.

plus can show histogram of dead objects (histograms of all and live requested, then difference is calculated)
plus can show N top buckets in histogram

More details

stcap, stcpy, ssa and flame

These commands provide basic sample profiler capabilities. stcap produces hyper-dense stack trace dump (about 1000 compression rate compared to text format) and ssa provides few reports over dump files. stcpy can copy data in archives produced by stcap (e.g. merging dumps or filtering selected threads).

So far following reports are available

sophisticated filtering (time, stack trace, thread name)
stack frame histogram with advanced filtering options
flame graph visualization (SVG or interactive HTML)
per thread summary (CPU usage, memory allocation, etc)
converting back to text format

Dump file can be also processed programatically.

More details

mx

This command allow you to do basic operations with MBean from command line.

It can

read MBean attributes
update MBean writeable attributes
invoke MBean operations (arguments are supported)
displays composite and tabular data in human readable format
use wild cards to shorten MBean names (e.g. *:*,name=CodeCacheManager instead of java.lang:type=MemoryManager,name=CodeCacheManager)
connect to local JVM processes by PID (e.i. any Java process, you do not need to enable JMX server)
connect to JMX using host:port (password authentication is supported)

More details