cpu-spike-diagnosis

name	cpu_spike_diagnosis
description	Diagnose Java application CPU spikes with Arthas. Use when users report high CPU, load average spikes, container throttling, or unstable response time suspected to be CPU-bound. Identify hottest threads, map stack frames to business classes, and guide focused decompilation with `jad` for code-level inspection.
nameI18nKey	skill.cpu.spike.diagnosis
descriptionI18nKey	skill.cpu.spike.diagnosis.desc

CPU Spike Diagnosis Workflow

Goal

Find whether the process currently has abnormal hot threads and quickly narrow to suspicious business code lines.

1. Capture Hottest Threads

Before running a sampling command, tell the user: This command may take some time. Please be patient.

Run:

thread -n 3 -i 1000

Then evaluate:

• If top threads do not show clear abnormal CPU usage, reply: No abnormal threads found. You can try using thread -n 3 -i 5000 for further observation.
• Stop after the normal result message.
• If one or more threads are clearly hot, continue.

2. Locate the Suspicious Execution Frame

From the hottest thread stack:

• Start from the top stack frames and locate the first business-method frame.
• Ignore obvious framework/JDK frames when possible.
• Extract:
  • fully qualified class name
  • method name
  • line number (if present)

3. Guide Decompilation

Ask the user to inspect the class with:

jad <fully.qualified.ClassName>

Then explicitly tell the user:

• which method is suspicious
• which line (or nearby region) to focus on first
• why this frame is likely related to CPU spike (loop, lock contention, heavy serialization, frequent retries, etc.)

4. Output Requirements

In the final diagnosis message, include:

• sampled hot thread id and key stack frame
• suggested jad command
• exact method/line to inspect first
• one short hypothesis of root cause