Production Bugs

Why can’t an iframe be used to selectively display only specific elements (e.g., titles) from a cross-origin HTML page using HTML/CSS alone?

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# Why can’t an iframe selectively display specific elements (like titles) from a cross-origin page with HTML/CSS alone? ## Summary * * User attempted to embed a cross-origin webpage via `<iframe>` into a fixed container while hiding non-title content using HTML/CSS only * Allowed constraints: Only HTML, CSS, and iframe elements * Disallowed constraints: JavaScript, … Read more

webclient proxy – connection time out error

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# WebClient Proxy Configuration Leading to Connection Timeout ## Summary A timeout error occurred when using Spring WebClient configured with an HTTP proxy. Despite correctly setting the proxy host and port, requests consistently failed with connection timeouts. The issue arose in a Java application leveraging Project Reactor’s HttpClient. ## Root Cause – **Proxy configuration wasn’t … Read more

Batch crop a folder of videos?

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# Postmortem: Batch Video Cropping Failure via FFmpeg Script ## Summary An automation attempt to crop multiple videos using FFmpeg in a Windows batch script failed due to unresolved placeholders in filter parameters and improper variable handling. The script executed without error detection but produced incorrect outputs. ## Root Cause – **Undefined crop parameters**: Placeholders … Read more

Twilio application delay

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# Twilio Application Hangup Synchronization Delay ## Summary – Users reported voice calls disconnecting immediately on cell phones when ended via the app UI, but the app UI continued showing an active call for ~20 seconds – The app correctly sent hangup requests to Twilio, but UI state updates were delayed – Twilio’s webhook response … Read more

nodriver chrome profile issue

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# Technical Postmortem: nodriver Chrome Profile Navigation Failure ## Summary User script launches a Chrome profile with `nodriver` but fails to navigate to the target URL. The browser process remains open indefinitely without triggering navigation or cleanup. ## Root Cause – Using `await` with synchronous `print()` function, causing an unhandled `TypeError` – Lack of error … Read more

site hosts and contact forms

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Technical Postmortem: Analysis of Limited Contact Form Support in Web Hosting Services Summary Web hosts frequently offer limited native contact form solutions despite their ubiquity Insufficient form functionality stems from security, cost, and architectural constraints Customers experience friction between convenience and customization needs Industry alternatives favor third-party integrations over native implementations Root Cause Technical constraints … Read more

Best practices to harden a Python experiment hook that triggers an external quota increase

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Best practices to harden a Python experiment hook that triggers an external quota increase Summary A minimal Python experiment hook randomly assigned users to control/treatment groups and called an external quota service. Production incidents occurred where duplicate quota increases, inconsistent assignment state, and traffic spikes caused: Permanent quota over-allocation to treated users Experiment group contamination … Read more

Method not found: ‘Void Microsoft.IdentityModel.Tokens.TokenValidationResult..ctor

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# Technical Postmortem: MissingMethodException in Blazor Web App During OIDC Token Validation ## Summary A Blazor Web App targeting .NET 9.0 failed during authentication with a `System.MissingMethodException` when calling `OpenIdConnectHandler.ValidateTokenUsingHandlerAsync()`. The application crashed at startup due to an incompatible version of `Microsoft.IdentityModel.Tokens`, specifically related to the `TokenValidationResult` constructor signature. Key details: – Exception: `Method not … Read more

Is robot framework able to test that something is *not* happening?

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# Postmortem: Handling Negative Assertions in Robot Framework for MQTT Event Verification ## Summary A critical gap was identified in automated tests for an IoT lighting system: Robot Framework had no explicit mechanism to confirm the **absence** of an expected MQTT message within a defined time window during night-mode operations. This led to incomplete verification … Read more

How to make a SQL query on a field which can be NULL and values, and only chose the largest value if possible

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# Postmortem: Incorrect Handling of NULL in SQL MAX Queries ## Summary An incorrect SQL query attempted to retrieve records with the largest non-NULL value in column `fd`, falling back to NULL values when no non-NULL data existed. The query failed due to improper NULL handling in comparison logic, yielding no results when NULL values … Read more