script

Some Shell for console problem

Java Thread CPU Monitor Script

script mointor_java_cpu.sh

Purpose

This script monitors a Java process and automatically captures thread dumps when CPU usage exceeds athreshold. It provides:

• Full thread stack traces
• Top N high CPU consuming threads
• Thread statistics report (states, types, deadlock detection)

Usage

./monitor_cpu.sh <Java_PID> [CPU_Threshold] [Check_Interval] [Top_Threads] [Stack_Lines]

Parameters

Parameter	Required	Default	Description
Java_PID	Yes	-	Java process ID
CPU_Threshold	No	50	CPU threshold percentage to trigger snapshot
Check_Interval	No	5	Check interval in seconds
Top_Threads	No	10	Number of top CPU threads to capture
Stack_Lines	No	20	Stack trace lines per thread

Examples

Basic Usage (Default Settings)

# Monitor PID 12345, capture when CPU > 50%
./monitor_cpu.sh 12345

Custom Threshold

# Trigger snapshot when CPU > 80%
./monitor_cpu.sh 12345 80

Custom Check Interval

# Check every 3 seconds, trigger at 60% CPU
./monitor_cpu.sh 12345 60 3

Capture More Threads

# Capture top 20 threads with 30 lines of stack trace
./monitor_cpu.sh 12345 50 5 20 30

Low Threshold Monitoring

# Sensitive monitoring: trigger at 30% CPU
./monitor_cpu.sh 12345 30 2 15 25

Output Files

When CPU exceeds threshold, 3 files are generated in ./thread_snapshots/:

1. jstack_TIMESTAMP_cpuXX.X.txt

Complete thread dump from jstack

2. threads_TIMESTAMP_cpuXX.X.txt

Top N high CPU threads with stack traces === High CPU Threads at Thu Feb 12 15:47:00 CST 2026 === Total Process CPU: 78.5% Top 10 threads by CPU usage

┌─────────────────────────────────────────────
│ Thread ID: 4168 (0x1048) - CPU: 45.2%
└─────────────────────────────────────────────
"http-nio-2012-exec-205" #542 daemon prio=5...

3. stats_TIMESTAMP_cpuXX.X.txt

Thread statistics report === Thread Statistics Report === Total Threads: 542

Thread States: RUNNABLE 12 ( 2.2%) TIMED_WAITING 480 ( 88.6%) WAITING 45 ( 8.3%) BLOCKED 5 ( 0.9%)

Thread Types (Top 10): http-nio-2012-exec 200 RabbitListener 10

Deadlock Detection: ✓ No deadlock detected

Real-World Scenarios

Production Issue Investigation

# Aggressive monitoring for troubleshooting
./monitor_cpu.sh 12345 40 2 15 30

Performance Baseline

# Capture only severe cases
./monitor_cpu.sh 12345 90 10 5 15

Memory Leak Detection

## Frequent checks with detailed stacks
./monitor_cpu.sh 12345 50 3 20 50

Tips

• Run in background: nohup ./monitor_cpu.sh 12345 &
• Stop monitoring: Press Ctrl+C or kill <script_pid>
• View latest snapshot: ls -t thread_snapshots/stats_*.txt | head -1 | xargs cat
• Find Java PID: jps -l or ps aux | grep java