Essential Linux and Java Debugging Tools for Rapid Issue Diagnosis

Introduction

In daily work many obscure issues arise, and a set of handy tools can dramatically speed up troubleshooting. This article records useful commands and utilities as a personal notebook and a shared resource.

Linux Command Tools

tail – most commonly used as tail -300f shopbase.log to view the last 300 lines and follow new writes.

grep – various examples for searching files, multiple files, directories, case‑insensitive, include/exclude patterns, and range matching.

awk – basic printing, record numbers, field numbers, and pattern matching examples.

find – examples for searching by name, type, size, permissions, and time attributes across multiple directories.

Specialized Tools

pgm – batch query logs, e.g.,

pgm -A -f vm-shopbase 'cat /home/admin/shopbase/logs/shopbase.log.2017-01-17|grep 2069861630'

.

tsar – Alibaba’s own data collection tool for historical and live metrics. Commands: tsar, tsar --live, tsar -d 20161218, and metric‑specific options such as tsar --mem, tsar --cpu.

top – combined with ps -ef | grep java and top -H -p pid to inspect threads.

Java Debugging Utilities

btrace – production‑grade tracing. Example shows how to print stack traces when ArrayList.add is called and the list size exceeds 500.

Greys – provides commands like sc -df xxx for class details and trace class method for method‑level timing.

JProfiler – commercial profiler for deep performance analysis (link provided).

eclipse MAT – memory analysis plugin for Eclipse.

Additional Java Tools

jps – list Java processes with command sudo -u admin /opt/taobao/java/bin/jps -mlvV.

jstack – obtain thread dumps, both standard and native+java stack.

jinfo – view JVM startup flags.

jmap – heap inspection and dump generation.

jstat – monitor GC utilization with jstat -gcutil pid 1000.

jdb – command‑line debugger for remote debugging.

CHLSDB – low‑level JVM debugging tool.

Other Helpful Utilities

maven helper – commands to display dependency trees and resolve conflicts.

VM options – use -XX:+TraceClassLoading or -verbose to trace class loading.

RateLimiter – Guava utility to limit QPS, useful when an upstream service requires a maximum request rate.

System‑Level Checks

When a Java process disappears, sudo dmesg | grep -i kill can reveal OOM‑killer activity. The log shows the process being killed due to memory pressure, and the command to convert dmesg timestamps to real time is provided.