Mark Zhu's Blog

Digital Zen: How I Tamed the Chaos of My Gadgets with Homebox

labile.zhu@gmail.com (Mark Zhu) — Tue, 20 Jan 2026 08:12:15 +0800

As a software engineer, my life has always been a blend of the digital and the physical. By day, I build complex architectures for large corporations, helping them manage their vast digital assets and streamline operations. By night (and on weekends), I’m a tinkerer. Whether it’s writing a custom script to automate my lighting, setting up a cluster of Raspberry Pi servers in my basement, or performing a DIY oil change on my car, I find immense joy in hands-on projects.

Linux: Everything is a file; peekfd: peek write/read of every file

labile.zhu@gmail.com (Mark Zhu) — Sat, 06 Jul 2024 23:12:15 +0800

Overview

Introduction

Most of the data flows in Linux, including inter-process communication, sockets, etc., are implemented through file descriptors (fd) reading and writing. When troubleshooting, if you can peek at the flow of fd, many problems can be quickly proved/falsified. This article introduces an old tool peekfd, which can complete this task in a certain environment.

Problems I encountered

I talked about a scenario in 《I Lost to AI - A Brief Note on a Parent-Child Process Interlocking Trap, I Digged It Myself》. The following is a diagram of the parent-child relationship of the process. I want to use kill -QUIT $ (Why not jstack?) to view the jvm stack. Ideally, kill -QUIT $test_case_jvm will make test cases jvm print a stack dump to stdout, and then maven jvm will also copy and print it out. But the reality is that maven jvm eats the stack dump output of test cases jvm and does not spit it out.

How an Asian Dad Keeps Learning English After a Layoff from an English-Speaking Workplace

labile.zhu@gmail.com (Mark Zhu) — Sat, 20 Jan 2024 08:12:15 +0800

I’m an Asian Dad living in Mainland China. I was recently laid off from an English-speaking workplace due to geopolitical factors. However, I am determined to continue improving my English skills, even without the daily immersion of a professional English environment.

Why keep learning English?

English skills are crucial for my career growth and personal development for several reasons:

Global Job Opportunities
English is the lingua franca of the global tech industry. Proficiency opens doors to international teams, global job markets, and collaborative projects that span multiple countries.

A Complete Guide of 'ss' Command Output Metrics - TCP Connection Inspecting Tool

labile.zhu@gmail.com (Mark Zhu) — Sun, 10 Sep 2023 01:12:15 +0800

Introduction

Understanding metrics from Linux ss command output.

I am not a network expert, but after years of troubleshooting network problems in production and test environments, I no longer want to muddle through, so I record what I have learned. Due to limited understanding of TCP stack implementation, the content is for reference only.

ss is a perfect tool to inspect TCP connection level statistics. But it is not well-documented. This article tries to explain the output of ss and how to read the metrics from the ss output.

Envoy WASM Network Filter to fix illegal HTTP Header

labile.zhu@gmail.com (Mark Zhu) — Sat, 11 Jun 2022 23:12:15 +0800

The story

The story takes place in the summer of 2022 AD. God (pseudonym) found that the normal HTTP request before the introduction of Istio was responded with HTTP status code 400 after the introduction of Istio Gateway. The traffic in question has HTTP headers that do not comply to the HTTP 1.1 specification. For example, there is an extra space before the colon:

GET /headers HTTP/1.1\r\n
Host: httpbin.org\r\n
User-Agent: curl/7.68.0\r\n
Accept: */*\r\n
SpaceSuffixHeader : normalVal\r\n

After begging God to fix the problem, “innocent” programmers prepared for the worst, trying to build a Noah’s Ark.