Posts Tagged ‘Debugging’
[DotJs2024] Your App Crashes My Browser
Amid the ceaseless churn of web innovation, a stealthy saboteur lurks: memory leaks that silently erode browser vitality, culminating in the dreaded “Out of Memory” epitaph. Stoyan Stefanov, a trailblazing entrepreneur and web performance sage with roots at Facebook, confronted this scourge at dotJS 2024. Once a fixture in optimizing vast social feeds, Stoyan transitioned from crisis aversion—hard reloads post-navigation—to empowerment through diagnostics. His manifesto: arm developers with telemetry and sleuthing to exorcise these phantoms, ensuring apps endure without devouring RAM.
Stoyan’s alarm rang true via Nolan Lawson’s audit: a decade’s top SPAs unanimously hemorrhaged, underscoring leaks’ ubiquity even among elite codebases. Personal scars abounded—from a social giant’s browser-crushing sprawl, mitigated by crude resets—to the thrill of unearthing culprits sans autopsy. The panacea commences with candor: the Reporting API, a beacon flagging crashes in the wild, piping diagnostics to endpoints for pattern mining. This passive vigilance—triggered on OOM—unmasks field frailties, from rogue closures retaining DOM vestiges to event sentinels orphaned post-unmount.
Diagnosis demands ritual: heap snapshots bracketing actions, GC sweeps purifying baselines, diffs revealing retainers. Stoyan evangelized Memlab, Facebook’s CLI oracle, automating Puppeteer-driven cycles—load, act, revert—yielding lucid diffs: “1,000 objects via EventListener cascade.” For the uninitiated, his Recorder extension chronicles clicks into scenario scripts, demystifying Puppeteer. Leaks manifest insidiously: un-nullified globals, listener phantoms in React class components—addEventListener sans symmetric removal—hoarding callbacks eternally.
Remediation rings simple: sever references—null assignments, framework hooks like useEffect cleanups—unleashing GC’s mercy. Stoyan’s ethos: paranoia pays; leaks infest, but tools tame. From Memlab’s precision on map apps—hotel overlays persisting post-dismiss—to listener audits, vigilance yields fluidity. In an age of sprawling SPAs, this vigilance isn’t luxury but lifeline, sparing users frustration and browsers demise.
Unveiling Leaks in the Wild
Stoyan spotlighted Reporting API’s prowess: crash telemetry streams to logs, correlating OOM with usage spikes. Nolan’s Speedline probe affirmed: elite apps falter uniformly, from unpruned caches to eternal timers. Proactive profiling—snapshots pre/post actions—exposes retain cycles, Memlab automating to spotlight listener detritus or closure traps.
Tools and Tactics for Eradication
Memlab’s symphony: Puppeteer orchestration, intelligent diffs tracing leaks to sources—e.g., 1K objects via unremoved handlers. Stoyan’s Recorder eases entry, click-to-script. Fixes favor finality: removeEventListener in disposals, nulls for orphans. Paranoia’s yield: resilient apps, jubilant users.
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[DevoxxGR2024] The Art of Debugging Inside K8s Environment at Devoxx Greece 2024 by Andrii Soldatenko
At Devoxx Greece 2024, Andrii Soldatenko, a seasoned software engineer and tech evangelist at Dynatrace, delivered an engaging presentation on mastering the art of debugging within Kubernetes (K8s) environments. With a blend of humor, practical insights, and real-world strategies, Andrii illuminated the complexities of troubleshooting cloud-native applications. Drawing from his extensive experience, he provided actionable techniques to enhance debugging efficiency, making the session a valuable resource for developers navigating the intricacies of Kubernetes. His talk emphasized proactive design, robust tooling, and a systematic approach to resolving issues in distributed systems.
The Challenges of Debugging in Kubernetes
Andrii began by acknowledging the inherent difficulties of debugging in modern cloud-native environments. Unlike traditional development, where a local debugger suffices, Kubernetes introduces layers of complexity with containers, pods, and distributed architectures. He humorously outlined his “eight stages of debugging,” from denial (“this can’t happen”) to self-realization (“I wrote this code”), resonating with developers who face similar emotional journeys. These stages underscore the psychological and technical hurdles of troubleshooting in K8s, where issues often stem from accidental complexities like misconfigured resources or network policies.
The dynamic nature of Kubernetes, with its orchestration of pods, nodes, and services, demands a shift in debugging mindset. Andrii emphasized that while writing YAML manifests for K8s is straightforward, ensuring they function as intended is not. He highlighted the absence of comprehensive debugging guides, noting that most literature focuses on deployment rather than troubleshooting. This gap inspired his talk, which aimed to equip developers with practical strategies to diagnose and resolve issues effectively.
Strategies for Effective Debugging
To tackle Kubernetes debugging, Andrii proposed a structured approach, starting with a high-level mind map for assessing pod states. For instance, a pod in a “Pending” state might indicate resource shortages or port conflicts, while a “Crashing” pod could signal health probe failures. He focused on scenarios where pods are running but behaving unexpectedly, a common yet challenging issue. Andrii advocated revisiting init containers, which perform setup tasks like data migrations. By temporarily replacing their commands with a sleep directive, developers can use kubectl exec to inspect the container’s state, checking volumes, permissions, or network access.
For containers lacking debugging tools, Andrii introduced ephemeral containers, a Kubernetes feature since version 1.8 designed for interactive troubleshooting. By launching an ephemeral container with tools like netcat or a debugger, developers can inspect a pod’s state without altering its primary container. He shared a practical example of debugging a Go application by sharing process namespaces, allowing access to the application’s processes. This approach enables setting breakpoints and navigating code, even in minimal, distroless containers.
Leveraging Tools for Enhanced Debugging
Andrii showcased several tools to streamline Kubernetes debugging. He recommended building custom debug containers tailored to specific needs, such as including sqlite, python, or network utilities, and shared his own debug container on GitHub. For network-related issues, he highlighted a pre-existing container with tools like tcpdump, which simplifies packet inspection without requiring manual installations. Andrii also praised Stern, a CLI tool for tailing logs across multiple pods in a replica set, making it easier to trace requests and identify exceptions.
For developers using Visual Studio Code, Andrii demonstrated remote debugging by configuring a launch.json file to connect to a Kubernetes pod. By exposing a debug port and using tools like Telepresence, developers can intercept cluster traffic and test changes locally, bypassing slow CI/CD cycles. He also highlighted K9s, a terminal-based UI for Kubernetes, with a custom plugin for initiating debug sessions via kubectl debug. These tools collectively enhance efficiency, allowing developers to focus on problem-solving rather than manual configuration.
Best Practices for Proactive Debugging
Andrii concluded with actionable best practices to prevent and address debugging challenges. He stressed embedding version information, like Git commit SHAs, into container images to synchronize codebases during remote debugging. Scaling down traffic to a single pod ensures consistent debugging sessions, avoiding request distribution across replicas. He also advocated for a blameless culture, where developers use debuggers to slow down and analyze issues methodically rather than rushing to fix symptoms.
By sharing his GitHub repository and additional resources, Andrii encouraged attendees to experiment with these techniques. His talk was a compelling call to action for developers to embrace robust debugging practices, ensuring resilience and reliability in Kubernetes environments. Through practical demonstrations and a lighthearted approach, he demystified the complexities of cloud-native debugging, empowering developers to tackle issues with confidence.
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[NodeCongress2021] Instrumenting Node.js Internals – Alejandro Oviedo
Delving into the intricacies of runtime diagnostics reveals a persistent challenge for Node.js developers: unraveling opaque behaviors in live applications without invasive alterations. Alejandro Oviedo, a backend specialist from Buenos Aires, confronts this head-on by unveiling “instrument,” an open-source utility he crafted to illuminate network flows, filesystem interactions, and module loadings. This innovation stems from his encounters with elusive glitches, where conventional logging falls short, compelling a quest for non-disruptive observability.
Alejandro’s journey underscores a universal frustration—debugging sans exceptions or traces leaves one adrift, akin to navigating fog-shrouded waters. Even in controlled dev setups, grasping async invocations or dependency chains demands more than intuition. His tool intervenes subtly, wrapping native modules like HTTP, HTTPS, or FS to log invocations without reshaping source code, thus preserving original outputs while appending diagnostic summaries.
Enhancing Visibility Through Modular Wrappers
At the heart of instrument lies a configuration-driven approach, where users specify modules in an instrument.config.js file—HTTP for endpoint reconnaissance, REQUIRE for dynamic imports. Alejandro demonstrates with npm’s version query: invoking via instrument yields the anticipated 8.2.1 for Mocha, trailed by a concise report on GET requests to registry.npmjs.org, complete with user-agent headers and CI flags. This granularity exposes externalities, from URL patterns to payload details, sans performance penalties in non-prod realms.
Extending to refactoring scenarios, imagine auditing dynamic loads in an HTTP server; static analyzers falter against runtime evaluations, but instrument excels, flagging module_a.js imports across probes. Alejandro stresses its dev-centric ethos: add as a devDependency, execute with npx instrument node app.js, and harvest insights effortlessly. Caveats abound—overhead precludes prod use, and nascent bugs invite community scrutiny via GitHub.
Yet, this simplicity belies profound utility. By demystifying internals, developers sidestep trial-and-error marathons, accelerating triage from hours to moments. Alejandro’s creation not only empowers solo coders but fosters collaborative ecosystems, where shared configs standardize diagnostics across teams. In an era of sprawling Node.js deployments, such tools bridge the observability chasm, ensuring applications hum reliably under scrutiny.
Fostering Community-Driven Refinements
Alejandro invites scrutiny, urging PRs and issues on the repository, while teasing a Q&A for deeper dives. His Buenos Aires roots and international contributions—local meetups to global forums—infuse the project with grassroots vigor, mirroring Node.js’s collaborative spirit. As environments evolve, instrument’s extensibility promises adaptations, perhaps integrating with APMs for holistic tracing.
Through this lens, troubleshooting morphs from art to science, equipping practitioners to dissect and mend with precision. Alejandro’s endeavor reminds us: true resilience blooms from visibility, not obscurity.
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[NodeCongress2021] Can You Change the Behavior of a Running Node.js Process From the Outside? – Vladimir de Turckheim
Runtime modifications to live applications represent a fascinating frontier in Node.js engineering, where traditional redeployments yield to dynamic interventions. Vladimir de Turckheim, a seasoned Node.js collaborator, delves into this realm, demonstrating techniques to alter process conduct without code alterations or restarts. His session reveals the debugger’s untapped potential, transforming it from a mere inspection tool into a conduit for real-time behavioral shifts.
Vladimir begins with a relatable scenario: a bare-bones HTTP server lacking logs, emblematic of hasty development oversights. Rather than refactoring and redeploying, he advocates injecting logging logic externally, leveraging Node.js’s signal-handling capabilities. By emitting SIGUSR1, the process enters debug mode, exposing a WebSocket endpoint for remote connections— a feature ripe for production diagnostics, as Vladimir notes in his Screen blog contributions on memory leak hunting.
Harnessing the DevTools Protocol for Introspection
Central to Vladimir’s methodology is the Chrome DevTools Protocol, the backbone of Node.js debugging. Forgoing graphical interfaces, he employs programmatic access via the inspector module, querying V8’s heap for object introspection. This low-level API enables pinpointing instances—like an HTTP server’s singleton—through prototype traversal and property enumeration, yielding object IDs as memory pointers.
Vladimir’s live demo exemplifies this: post-debug activation, a secondary Node.js injector script evaluates expressions remotely, first globalizing a patching function on the process object for universal accessibility. Subsequent calls invoke this function on the server instance, swapping ‘request’ event listeners with wrappers that prepend console logs—capturing methods and URLs—before delegating to originals. This monkey-patching preserves event emission order, ensuring seamless augmentation.
Such precision stems from protocol commands like Runtime.evaluate and Runtime.callFunctionOn, which execute snippets in the target’s context. Vladimir cautions on cleanup—releasing object IDs and closing sessions via inspector.close—to avert leaks, underscoring the approach’s suitability for controlled environments with SSH access, where administrative privileges mitigate security risks.
Practical Implications and Beyond Debugging
While ostensibly a code injection showcase, Vladimir reframes the talk as a tribute to DevTools’ extensibility. Beyond logging, it facilitates bespoke profilers or heap dumps for elusive issues, bypassing UI limitations in IDEs like VS Code. For production, this enables non-intrusive observability, aligning with Screen’s mission of code-agnostic server hardening.
Vladimir concludes by encouraging custom tool-building, from granular CPU sampling to event tampering, all grounded in the protocol’s robustness. His narrative not only equips attendees with actionable dark arts but also elevates debugging from reactive firefighting to proactive mastery, fostering resilient Node.js ecosystems.
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[DevoxxFR2015] Unlocking Chrome OS: Insights from Its Open-Source Code
François Beaufort, a Chromium Evangelist based in Paris, delivered an engaging session at Devoxx France 2015, sharing ten key lessons gleaned from diving into the open-source code of Chrome OS. Despite a last-minute rush to the stage, François captivated the audience with practical insights into Chrome OS’s architecture, emphasizing the power of exploring source code to understand and debug this web-centric operating system.
Exploring Chrome OS’s Open-Source Roots
François introduced Chrome OS, the operating system powering Chromebooks, built on the open-source Chromium OS project. He highlighted its web-based nature, where applications leverage HTML, CSS, and JavaScript. By enabling a specific flag, developers can right-click to inspect elements, revealing the underlying code of Chrome OS applications, such as the wallpaper app. This transparency allows direct debugging, transforming how developers interact with the system.
This accessibility, François noted, empowers developers to troubleshoot effectively.
Practical Debugging with Source Code
Through a real-world example, François recounted debugging a broken Linux distribution app, Gestan, on a Chromebook. By accessing the JavaScript console in the Dev Channel, he identified a compatibility issue with a Chrome update, enabling a swift fix. This approach bypasses traditional bug reporting, allowing developers to collaborate directly with maintainers. His session underscored the value of open-source code for rapid problem-solving.
François’s insights inspire hands-on exploration of Chrome OS.
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[DevoxxBE2013] Riddle Me This, Android Puzzlers
Stephan Linzner and Richard Hyndman, Google Android Developer Advocates, unravel enigmatic Android behaviors through interactive puzzles. Stephan, an automation aficionado and runner, teams with Richard, a 12-year mobile veteran from startups to operators, to probe component lifecycles, UI quirks, and KitKat novelties. Their session, blending polls and demos, spotlights content providers’ primacy, ViewStub pitfalls, and screen recording tools, arming developers with debugging savvy.
Android’s intricacies, they reveal, demand vigilance: from process spawning to WebView debugging. Live polls engage the audience, transforming head-scratchers into teachable moments.
Component Creation Order and Lifecycle
Stephan kicks off with a poll: which component initializes first post-process spawn? Hands favor activities, but content providers lead—crucial for data bootstrapping.
Richard demos service lifecycles, warning against onCreate leaks; broadcasts’ unregistered crashes underscore registration discipline.
UI Rendering Quirks and Optimizations
ViewStub inflation puzzles Stephan: pre-inflate for speed, but beware null children post-inflation. Richard explores ListView recycling, ensuring adapters populate recycled views correctly to avoid visual glitches.
These gotchas, they stress, demand profiler scrutiny for fluid UIs.
KitKat Innovations and Debugging Aids
KitKat’s screen recording, Richard unveils, captures high-res videos sans root—ideal for demos or Play Store assets. Stephan spotlights WebView debugging: Chrome DevTools inspect remote views, editing CSS live.
Monkey tool’s seeded crashes aid reproducible testing, simulating user chaos.
Interactive Polls and Community Insights
Polls gauge familiarity with overscan modes and transition animations, fostering engagement. The duo fields queries on SurfaceView security and WebView copies, clarifying limitations.
This collaborative format, they conclude, equips developers to conquer Android’s riddles.
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[DevoxxBE2012] The Chrome Dev Tools Can Do THAT
Ilya Grigorik, a Google web performance engineer and developer advocate, unveiled advanced capabilities of Chrome Developer Tools. Ilya, focused on accelerating the web, overwhelmed attendees with tips, dividing into inspection/debugging and performance analysis.
He encouraged hands-on exploration via online slides, emphasizing tools’ instrumentation for pinpointing bottlenecks.
Starting with basics, Ilya showed inspecting elements, modifying DOM/CSS live, and using console for JavaScript evaluation.
Advanced features included remote debugging for mobile, connecting devices to desktops for inspection.
Inspection and Debugging Essentials
Ilya demonstrated breakpoints on DOM changes, XHR requests, and events, pausing execution for analysis.
Color pickers, shadow DOM inspection, and computed styles aid UI debugging.
Console utilities like $0 for selected elements, querySelector, and table formatting enhance interactivity.
JavaScript Profiling and Optimization
CPU profilers capture call stacks, revealing hot spots. Ilya profiled loops, identifying inefficiencies.
Heap snapshots detect memory leaks by comparing allocations.
Source maps map minified code to originals, with pretty-printing for readability.
Network and Resource Analysis
Network panel details requests, with filters and timelines. Ilya explained columns like status, size, showing compression benefits.
WebSocket and SPDY inspectors provide low-level insights.
HAR exports enable sharing traces.
Timeline and Rendering Insights
Timeline records events, offering frame-by-frame analysis of layouts, paints.
Ilya used it to optimize animations, enabling GPU acceleration.
CSS selectors profile identifies slow rules.
Auditing and Best Practices
Audits suggest optimizations like minification, unused CSS removal.
Extensions customize tools further.
Low-Level Tracing and Customization
Chrome Tracing visualizes browser internals, instrumentable with console.time for custom metrics.
Ilya’s session equipped developers with powerful diagnostics for performant, debuggable applications.