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Fixing a kubelet memory leak in Kubernetes 1.36
5 days ago
- The author discovered a memory leak in Kubernetes 1.36 on a small test cluster, revealed due to high memory pressure.
- Investigation showed the kubelet process itself was growing in memory usage, not the application pods.
- Heap profiling using Go's pprof identified nearly a million leaked contexts as the primary cause, consuming most memory.
- A code change in Kubernetes 1.36 introduced a context leak by overwriting cancel functions without canceling old contexts in the pod reconciliation loop.
- AI tooling (Codex) helped pinpoint the regression in the codebase, specifically in the startPodSync function.
- A patch was developed and submitted; it was simplified to revert the immediate leak after integration test failures revealed additional context issues.
- The Kubernetes team was responsive, with the fix merged into the master branch for v1.37 and backported to v1.36.
- Restarting kubelet temporarily resolved memory pressure, but the underlying leak persisted until patched.
- Lessons include the value of heap profiling, the time dimension in long-running systems, and infrastructure-level issues.
- A one-liner command to monitor kubelet memory usage showed a significant drop from 974 MiB to 110 MiB after restart.
DLL that was not present in memory despite not being formally unloaded
7 days ago
- A bug reported that shell32.dll was causing crashes in a third-party program, but investigation revealed shell32 was a victim.
- Crash dumps showed a stack overflow due to a recursive exception handling death spiral, starting from an access violation in combase!CoTaskMemFree.
- Analysis found that combase.dll had been forcibly unloaded from memory (likely via VirtualFree), not by FreeLibrary, causing subsequent calls to fail.
- Shell32 was blamed as it was the first to call into the unloaded combase.dll during process termination, triggering the crash loop.
- Reviewing 100 recent crashes showed 46% were due to similar rogue DLL force-unloads, with different DLLs affected, indicating a bucket spray issue.
- The root cause is unknown, but theories point to memory corruption or uninitialized variables in the third-party program or other components.
- Wil comments suggest avoiding static object destruction during shutdown and note existing shutdown-aware types in Microsoft code.
Underappreciated Builtin: Grand Unified Debugger
5 days ago
- The Grand Unified Debugger (GUD) in Emacs is an underappreciated built-in feature that supports multiple debuggers like GDB, LLDB, Perl, Java, Python, and others.
- A demo using GDB with a Fibonacci program shows how to set breakpoints via fringe clicks, use toolbar buttons (Run, Next Line, Step Line, Up/Down Stack), and manage breakpoints in a dedicated window.
- GUD provides features like an I/O window for output, variable inspection by hovering, a locals window, and variable watching for automatic updates when values change.
It's not me, it's the compiler
5 days ago
- A programmer discovered a compiler bug in Rust while refactoring a JavaScript engine's parser.
- The bug was in a function where using 'x as u32' for boolean addition caused incorrect behavior, but using an explicit if-else worked.
- Assembly inspection confirmed the compiler omitted an increment instruction, leading to a miscompilation.
- The issue was reported as 'Suspected miscompilation' and quickly fixed within 18 hours by the Rust community.
- The bug was classified as p-critical and i-miscompile, highlighting rare but serious compiler errors.
No laptop? No problem. Code on the Go brings the debugger to your phone
3 days ago
- Code on the Go (CoGo™) enables debugging on a single Android device without a PC, cable, or external connections.
- It uses a local socket-based approach with Java Debug Wire Protocol (JDWP) instead of the traditional ADB bridge model.
- Privileged access is bootstrapped via a modified version of Shizuku, leveraging wireless debugging pairing for shell-level access.
- The target app is launched in debug mode using the --attach-agent flag to inject libjdwp.so, establishing a debug connection.
- The IDE communicates via JDI using sun-jdi.jar from AOSP, enabling breakpoints, stepping, variable inspection, and editing.
- Current limitations include Java-only debugging, primitive variable editing only, user-dependent bootstrapping, and reliance on system JDWP.
- Future plans include Kotlin support, conditional breakpoints, expression evaluation, and attaching to running processes.
The Safari MCP server for web developers
3 days ago
- Safari MCP server introduced in Safari Technology Preview 247.
- Enables agents to access browser data (DOM, network requests, screenshots, console logs).
- Speeds up debugging by reducing context switching between browser and terminal.
- Use cases include checking rendering, improving Safari compatibility, analyzing performance, and verifying accessibility.
- Available tools include console messages, network requests, page interactions, screenshots, and JavaScript evaluation.
- Setup requires installing Safari Technology Preview and enabling developer features.
- Local-only operation ensures data privacy and no external network calls.
- Goal is to enhance AI-assisted web development workflows for Safari.
Game Boy Advance Dev: Logging to the Console
a day ago
- mGBA allows GBA developers to use printf-like functionality for debugging by writing to specific memory-mapped registers.
- Logging is enabled by writing 0xC0DE to REG_LOG_ENABLE, writing the message to REG_LOG_BUFFER, and then sending a log level to REG_LOG_SEND.
- The log levels include ERROR, WARNING, INFO, and DEBUG, with each corresponding to a specific value for the REG_LOG_SEND register.
- Logs can be viewed in mGBA's Tools > View logs... window or output to the terminal if launched from the command line with --log-level.
- Advanced logging features include printf-style formatting using vsnprintf and conditional compilation with a macro to exclude logging from release builds.

Hasty Briefsbeta

#debugging

Fixing a kubelet memory leak in Kubernetes 1.36

DLL that was not present in memory despite not being formally unloaded

Underappreciated Builtin: Grand Unified Debugger

It's not me, it's the compiler

No laptop? No problem. Code on the Go brings the debugger to your phone

The Safari MCP server for web developers

Game Boy Advance Dev: Logging to the Console