Production Bugs

Yearly seasonality with only 12 monthly points leads to different results due to version dependencies

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Summary Yearly seasonality with only 12 monthly data points leads to under-identified models in Prophet, causing version-dependent results. Different versions of Prophet and cmdstanpy converge to varying trend-seasonality decompositions, resulting in unstable forecasts. No warning or safeguard exists for this scenario, posing risks in production. Root Cause Under-identification: 12 monthly points (one annual cycle) are … Read more

Can I do this in Tkinter? Change text-format of numbers in cells excel-like?

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Summary This incident examines a common UI‑design misunderstanding: trying to apply Excel‑style per‑cell text formatting inside a Tkinter Listbox, which fundamentally does not support that capability. The engineering failure wasn’t in the code but in the assumption that the widget could do something it was never designed to do. Root Cause The root cause was … Read more

MongoDB only stays running for a few days. Why? Main process exited, code=dumped, status=6/ABRT

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Summary MongoDB v8.0.17 on Ubuntu 24.04 crashes after a few days with core dump (signal=ABRT). The issue is caused by memory corruption leading to a segmentation fault, triggered by intensive write operations or large dataset handling. Root Cause Memory corruption in the MongoDB process, resulting in a segmentation fault. Triggered by high write throughput or … Read more

VS Code blue status bar appears when running my custom theme extension

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Summary The blue status bar issue in VS Code occurs when a custom theme extension is activated, despite no statusBar colors being defined in colors.json. This behavior is specific to the extension’s activation and does not occur with default themes. Root Cause The root cause is an unintended contribution in the extension’s package.json or an … Read more

Can System.Text.Json tolerate an unrecognized type discriminator during deserialization?

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Summary A deserialization failure occurred when System.Text.Json rejected an unknown type discriminator in a polymorphic payload. Instead of gracefully ignoring the unrecognized subtype, the serializer threw a NotSupportedException, preventing the object graph from being materialized. Root Cause The failure stems from how System.Text.Json enforces strict polymorphic type resolution: The interface IBar is marked with [JsonPolymorphic(IgnoreUnrecognizedTypeDiscriminators … Read more

analytics().logScreenView, custom definition not working in GA4

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Summary A custom eid parameter sent through analytics().logScreenView() appeared correctly in DebugView and in raw event payloads, but GA4 reports and Explorations showed incorrectly low counts. The issue was caused by sending a numeric parameter for a field that GA4 treats as a string, combined with GA4’s strict rules for custom dimensions and event-scoped parameters. … Read more

Colourful artifacts in browsers and plotting libraries

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Summary A long‑standing issue on Windows 7 can cause colourful rendering artifacts in browsers and plotting libraries. These artifacts typically appear as unexpected bands, gradients, or corrupted pixel regions—especially in GPU‑accelerated applications. This postmortem explains why this happens, why it persists across hardware vendors, and how senior engineers diagnose and resolve it. Root Cause The … Read more

SpringBoot Model Advice (already got the solution)

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Summary This incident examines a common early‑career design mistake in Spring Boot: modeling hierarchical data incorrectly. The engineer attempted to represent categories and subcategories using either two separate models or a single model with a parent_id. The confusion led to inconsistent behavior, difficulty saving entities, and unclear domain boundaries. Root Cause The root cause was … Read more

Is there a way to bypass hashes in the Databricks CLI when installing packages?

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Summary This incident centers on a pip hash‑mismatch failure when installing the Databricks Lakebridge transpiler (BladeBridge Transpile). Even though Lakebridge itself installed successfully, the transpiler installation failed because pip refused to install a wheel whose computed hash did not match the expected hash. This is a classic integrity‑verification failure triggered by strict hash‑pinning in the … Read more