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Coder Trainee

Experienced in Java and Python, we share and learn together. For submissions or collaborations, DM us.

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Latest from Coder Trainee

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Coder Trainee

Aug 31, 2026 · Artificial Intelligence

From Beginner to Pro: Mastering ComfyUI’s Node‑Based AI Image Generation

This article explains why ComfyUI outperforms traditional WebUI by offering a node‑based visual programming workflow, details its three core advantages, provides step‑by‑step installation and a first text‑to‑image pipeline, introduces essential plugins, high‑resolution commercial techniques, and shows how Java developers can use its API as a backend.

AI image generationComfyUIJava API

0 likes · 8 min read

From Beginner to Pro: Mastering ComfyUI’s Node‑Based AI Image Generation

Coder Trainee

Aug 29, 2026 · Backend Development

When @Transactional Goes Wrong: Misusing Transaction Propagation Leads to Deadlocks

A real‑world case shows that using @Transactional with the default REQUIRED propagation caused a long‑running transaction, frequent deadlocks, data inconsistency and higher timeout rates, and the article walks through the root cause, investigation steps, and practical fixes such as REQUIRES_NEW, self‑proxy calls, and async eventual consistency.

@TransactionalJavaSpring

0 likes · 9 min read

When @Transactional Goes Wrong: Misusing Transaction Propagation Leads to Deadlocks

Coder Trainee

Aug 28, 2026 · Backend Development

I Almost Got Fired Using Parallel Stream in Production

A production outage caused by Java 8 parallel streams exposed the dangers of the default commonPool, unlimited task queuing, and long‑running API calls, leading to 100% CPU, 30+ GC events per hour, and a near‑service collapse, which was resolved by custom thread pools, timeouts, and CompletableFuture alternatives.

CompletableFutureForkJoinPoolJava

0 likes · 7 min read

I Almost Got Fired Using Parallel Stream in Production

Coder Trainee

Aug 27, 2026 · Operations

How a DNS Resolution Failure Prompted a Full Network Layer Investigation

An intermittent DNS resolution failure caused third‑party API timeouts, leading to a step‑by‑step investigation that revealed an unstable public DNS server, and resulted in four practical solutions including switching DNS servers, adjusting JVM cache settings, adding hosts entries, and implementing retry logic.

DNSJVM cachehosts file

0 likes · 6 min read

How a DNS Resolution Failure Prompted a Full Network Layer Investigation

Coder Trainee

Aug 26, 2026 · Operations

How a Single Git Mistake Rolled Back Three Days of Production Code

A developer mistakenly ran a hard reset and forced push on the main branch, rolling back three days of production code; the article walks through the incident timeline, impact assessment, emergency recovery steps, root‑cause analysis, and preventive measures such as branch protection and safer Git commands.

Branch ProtectionDevOpsGit

0 likes · 7 min read

How a Single Git Mistake Rolled Back Three Days of Production Code

Coder Trainee

Aug 25, 2026 · Artificial Intelligence

Step-by-Step Guide to Installing DeepSeek Harness (dsh)

This tutorial walks you through installing DeepSeek Harness (dsh), covering Node.js version checks, quick one‑command setup, source‑code installation with pnpm, Docker options, and initial API key configuration for the web UI on your local machine.

DSHDeepSeekDocker

0 likes · 5 min read

Step-by-Step Guide to Installing DeepSeek Harness (dsh)

Coder Trainee

Aug 24, 2026 · Backend Development

How a Silent Infinite Loop Drained Our Database Connection Pool

The article walks through a real incident where a scheduled batch job contained an infinite while‑true loop, causing all 500 HikariCP connections to be held, slowing the application dramatically; it details the investigation steps, root‑cause analysis, and both emergency and long‑term fixes, plus a checklist to avoid similar bugs.

HikariCPJavaSpring

0 likes · 7 min read

How a Silent Infinite Loop Drained Our Database Connection Pool

Coder Trainee

Aug 21, 2026 · Operations

When Logs Fill the Disk: How I Cleared Three Days of Log Files

A production server hit 100% disk usage, prompting the author to use df, du and find to locate oversized log files, uncover missing rotation, excessive debug logging and a looping exception, then perform urgent cleanup and implement logrotate, log level adjustments, and Prometheus alerts to prevent recurrence.

LinuxLog ManagementTroubleshooting

0 likes · 7 min read

When Logs Fill the Disk: How I Cleared Three Days of Log Files

Coder Trainee

Aug 20, 2026 · Backend Development

How I Resolved a 1‑Million‑Message Kafka Consumer Backlog

When a Kafka topic’s consumer lag suddenly spiked to over one million messages, the author traced the issue to improper acknowledgment handling, implemented emergency scaling, corrected exception processing, added a dead‑letter queue, and created a reusable checklist to prevent future backlogs.

Consumer LagDead Letter QueueKafka

0 likes · 7 min read

How I Resolved a 1‑Million‑Message Kafka Consumer Backlog

Coder Trainee

Aug 19, 2026 · Backend Development

The “Ghost” Distributed Lock Issue: 3‑Day Debugging of Lock Failure

The article walks through a real production incident where a Redis‑based distributed lock silently failed, causing duplicate point awards, and details the step‑by‑step investigation, root‑cause analysis of transaction‑lock ordering, and three concrete remediation strategies.

RedisRedissonSpring @Transactional

0 likes · 9 min read

The “Ghost” Distributed Lock Issue: 3‑Day Debugging of Lock Failure