The CI failures that moved every time you reran them
How a moving set of Rails CI flakes exposed shared download state, Selenium stale-node retries, and specs asserting before the browser settled.
Tag: debugging
The callback that quietly doubled our database
A Rails after_save callback silently duplicated database rows: how the symptom appeared, why the obvious suspect was innocent, and the real root cause.
Rails UJS to Turbo: the event timing bug CI didn't catch
Migrating Rails UJS to Turbo can silently break submit buttons and resets in production, because Turbo's event timing and Promise handling differ from UJS.
Production Ruby Debugging: A Progressive Escalation Guide
A progressive escalation guide to debugging Ruby applications in Kubernetes production without restarting: rbspy, kubectl debug, signals, rbtrace, and gdb.
Tiny Puzzles for Testing and Debugging AI Agents
Small probe tasks for testing local AI agents: function calling, skill awareness, prompt-length pressure, cache behavior, and layer-by-layer debugging.
How I Finally Got Sentry to Create GitHub Issues (After 3 Hours of Clicking Around)
How to fix Sentry's GitHub integration when it shows connected but issues won't create, plus why linking Sentry errors to GitHub issues is worth the setup.
Fixing the Asia/Rangoon Postgres Error on Alpine Linux
If you recently updated your Docker images and were greeted by a PG::InvalidParameterValue: ERROR: time zone "Asia/Rangoon" not recognized, you aren't alone.
Why macOS ignores your manual DNS settings
On a managed MacBook, iCloud Private Relay and MDM scoped resolvers silently override manual DNS settings, and scutil --dns shows you which one is winning.
PostgreSQL on Ubuntu: install, user setup, and auth debugging
Install PostgreSQL from the PGDG repo on Ubuntu, set up a matching development role, and debug the password authentication failures Rails hits most.
Chrome's "blocked:other": why analytics scripts go silent
Chrome's "blocked:other" status silently kills analytics and error-tracking scripts, and proxying those requests through your own server is the fix.
Rails 8.1.1 + connection_pool 3.x: RedisCacheStore boot crash
A keyword-argument mismatch between Ruby 3.4 and connection_pool 3.x breaks RedisCacheStore at Rails 8.1.1 boot, fixed with a patch loaded before initializers run.
The Ghost in the Test Suite: Fixing Rails Database Cleanup
A flaky RSpec suite traced to a Rake task that commits data outside the per-test transaction, and how DatabaseCleaner's truncation strategy fixes it.
Ruby Debugging in VS Code: Shopify LSP, rdbg, and RSpec
How to wire up VS Code for Ruby debugging with the Shopify Liquid LSP, the rdbg debugger from Ruby's debug gem, and launch configs for RSpec, Minitest, and Cucumber.
Active Storage Variants: Multiple Sizes and Testing Pitfalls
Active Storage's variant API gets rough past the basic thumbnail case: multiple sizes, per-attachment metadata, and tests that break on file-not-found errors.
Troubleshooting pgpool Connection Termination in Kubernetes
Intermittent pgpool connection drops in Kubernetes usually trace to max_connections, idle timeouts, or NetworkPolicy issues, found layer by layer.
User Impersonation in Rails with the Pretender Gem
User impersonation lets an admin temporarily act as another user for debugging and support, and the pretender gem handles the current_user switch and session state.
GKE's Two Health Check Systems and the Premature 502
GKE deployments can pass every readiness probe and still serve 502s, because Kubernetes probes and the Cloud Load Balancer run two separate health checks.
When to Mock and When to Hit the Real Thing in Rails Tests
A practical breakdown of when to mock external dependencies in Rails tests versus using the real thing, built around the test pyramid, VCR, WebMock, and Pact.
How button_to Changed in Rails 7 (and Broke Our CSS)
Rails 7's button_to wraps a form around the button instead of rendering a plain input, which silently breaks existing CSS selectors and JavaScript click handlers.
How Rails Sessions Work with Warden and Cookies
Rails keeps users logged in by encrypting the whole session into a browser cookie, then lets Warden authenticate each request, which changes how you should test it.
Is Your Endpoint I/O Bound or CPU Bound?
How to tell whether a slow endpoint is I/O bound or CPU bound, using system monitors, timing, and cProfile, and why the fix differs for each.
Debugging Exceptions: Break on Throw, Not Catch-All
Catch-all exception handlers hide the real bug. Debuggers that pause on every thrown exception, caught or not, find it faster than logging ever will.
Frontend Error Handling: Catching What try/catch Misses
Why Sentry and Bugsnag catch more JavaScript errors than custom try/catch logic, and how to close the gap with global handlers and rejection listeners.
Nokogiri vs libxml2: Debugging a Dynamic Library Conflict
Why Nokogiri XPath queries failed in Docker but not on an M1 Mac: a libxml2 version mismatch caused by indirect dynamic library loading in Ruby.
Xiaomi "No Signal": Dialer Codes to ADB Logs
How to debug a "No Signal" or "No SIM" error on a Xiaomi phone, from dialer diagnostic codes through ADB logcat filters to EFS partition failures.
Debugging Transaction Deadlocks in Rails Tests: A Case Study
A Rails test suite hung intermittently until transactional tests, ActiveJob, and ActiveStorage turned out to be racing over the same locked rows.
Debugging in Ruby, Python, and PHP: byebug, pdb, and Xdebug
Compares Ruby's byebug, Python's pdb, and PHP's Xdebug side by side, with the core commands and a working example for each language.
Retry Strategies in Ruby: Exceptions vs. Conditional Checks
Comparing Ruby retry patterns, exception-based retry, conditional checks, and exponential backoff, and when each keeps performance acceptable.
5 Parameter Code Smells and How to Refactor Them
Five parameter-related code smells, from boolean flags to long argument lists, and the refactor that turns each function into one that does one thing.
Ordering by an Associated Column Without Breaking includes
Why ordering ActiveRecord results by an associated table's column breaks with includes, and how references, Arel, and left_joins fix it for good.
N+1 Queries in Rails: What Silently Breaks `includes`
How ActiveRecord's includes prevents N+1 queries in Rails, and the common mistakes with order, filtering, and pluck that silently break it.
Building a Test Suite: Pyramid, Layers, and What to Skip
A framework for deciding how much to test: the testing pyramid, layered test responsibility by architecture tier, and what makes test data good.
Testing Non-ASCII Fonts with Prawn and PDF::Inspector
How to debug Unicode font rendering in Ruby's Prawn PDF library and work around PDF::Inspector's limits when testing non-ASCII characters like it.
Android build and debug tips: jenv, ADB, and wireless debugging
Practical notes on Android build and debug workflow: managing Java versions with jenv, wireless ADB debugging, release signing, and logcat filtering.
Ruby object IDs, anonymous modules, and Rails cache errors
A Rails.cache TypeError on an anonymous module led into Ruby's Marshal restrictions and the relationship between object_id and C-level memory addresses.
Docker Buildx --on-error: drop into a shell when a build fails
The --on-error flag in Docker Buildx drops you into a shell inside the failing build step so you can inspect state instead of guessing from logs.
How to Debug Docker Image Builds
Practical techniques for debugging Docker image builds: BuildKit output flags, inspecting intermediate layers, nsenter tricks, and multi-stage build targets.
Running Multiple Processes in a Single Container
Six ways to run multiple processes in one Docker container, from GNU Parallel and Foreman to a custom entrypoint script, Supervisord, and tmux, with trade-offs.
Why Kaminari's Anonymous Modules Break Rails Caching
Why Rails caching raises TypeError: can't dump anonymous module with Kaminari-paginated collections, and how to trace and fix the module causing it.
Passing Sass Variables at Build Time with Webpack
How to inject a Sass variable, like a theme's primary color, at build time using a SASS_OPTIONS environment variable and a custom webpack additionalData function.
Upgrading React 16 to 17: Dependencies, Jest, and ESLint Fixes
A practical walkthrough of upgrading a React 16 app to React 17, covering dependency updates, Jest and Enzyme test fixes, and new ESLint warnings.
Fixing Multi-Tab Session Bugs with JWT and sessionStorage
How cookie-based session state breaks when a user opens multiple tabs in a single-page app, and how splitting auth into JWT plus sessionStorage fixes it.
adb shell pm: Managing Android Packages from the Command Line
How to use adb shell pm to list, install, uninstall, disable, and inspect Android packages, including removing bloatware without root.
How to Debug React Applications
A rundown of debugging React apps: React Developer Tools in the browser, inspecting React Native, and running Jest tests under a real debugger.
Integer Overflow and Floating-Point Precision: Ruby vs JS
Why 0.1 + 0.2 doesn't equal 0.3, how Ruby's arbitrary-precision integers avoid overflow, and how JavaScript's BigInt does the same for large integers.
Round Is Not Always What You Expect
Rounding the same float, 2.675, to two decimal places gives different answers in C#, PHP, Go, Python, JavaScript, and Ruby, for concrete reasons.
Upgrading to Rails 7.2: Four Breaking Changes We Hit
Four breaking changes we hit upgrading to Rails 7.2: show_exceptions, array-containment SQL, connection pool locking, and assert_enqueued_email_with.
Ruby's GVL vs Ractor: What Actually Runs in Parallel
Ruby's Global VM Lock serializes threads for CPU-bound work, and Ractor works around it with isolated memory, benchmarked here against threads and processes.
fail vs raise in Ruby: They're the Same Method
Ruby's fail is a plain alias for raise, both dispatch to the same Kernel method, confirmed here in the C source and with an lldb backtrace.
delete_all vs destroy_all in Rails: Callbacks and Associations
delete_all skips callbacks and dependent associations while destroy_all runs them, and picking the wrong one silently breaks counter caches and cascades.
Floating-Point Precision in Ruby: Why 0.1 + 0.33 ≠ 0.43
Ruby's 0.1 + 0.33 does not equal 0.43 because of binary floating-point rounding, and Rational, BigDecimal, and tolerance comparisons each fix it differently.
Inspecting Sidekiq Jobs from the Rails Console
Console-ready Ruby snippets to inspect Sidekiq queues, scheduled jobs, retry and dead sets, and currently running workers when the dashboard is not enough.
Production Debugging Techniques for Rails Apps
Practical production debugging techniques for Rails: log analysis, replicating production data, rbtrace live injection, feature-flagged debug modes, and replica apps.
Redis Memory Spikes: Tracking Down a Runaway Sidekiq Queue
How I traced a Redis memory jump from 130MB to 800MB back to an unthrottled Sidekiq integration, and the maxmemory, eviction, and unique-job fixes that followed.
A .irbrc Full of Ruby Debugging and Introspection Helpers
A collection of .irbrc helpers for tracing method calls, logging SQL queries, profiling code, and inspecting Ruby objects during Rails console debugging.
How to Set a Breakpoint on Devise's current_user Method
Why byebug can't break on Devise's metaprogrammed current_user method, and several ways to debug or patch a method that isn't in your source.
GCP 502 Errors from GKE Readiness Probe Failures
A GKE 502 with 'failed_to_pick_backend' traced back to readiness probes failing on every pod at once, and the liveness probe and anti-affinity fixes that resolved it.
When the OOM Killer Silently Kills a Background Job
A missed notification email traced back to the Linux OOM killer terminating a Sidekiq job mid-run, leaving a stuck Redis lock and no error logged anywhere.
Soft Delete in Rails: Discard vs ActsAsParanoid
A comparison of Discard and ActsAsParanoid, the two common Rails soft-delete gems, and the query and unscope pitfalls each one introduces.
How Rails Loads Your App: Rake, Console, Server, and Tests
What Rails actually loads when you run a rake task, the console, the server, or tests, and how to load rake tasks in each environment when you need them.
最令PHP初学者头痛的十四个问题及解决方案
PHP是一门强大且流行的服务器端脚本语言，但初学者在学习过程中可能会遇到一些常见问题。本文将列举并提供这些问题的解决方案。
域名解析服务探究与nslookup工具使用指南
在互联网世界中，域名解析是一项基础服务，它将用户友好的域名转换为机器可识别的IP地址。本文将介绍如何使用nslookup工具来查找提供域名解析服务的实体。