Architectural Breakdown: Installing Flask on Ubuntu 24.04
# Flask on Ubuntu 24.04: Why Your Simple Install Broke at 2 AM It was 2:47 AM when the alert hit. Our uWSGI workers on the new Ubuntu 24.04 staging box had started swapping. Not throttling, not complaining, full memory-pressure swap thrashing that turned a simple health check into a 12-second GET request. Load average read 8.4 on a 2-core instance with 8GB RAM, and half of that was occupied by a…
At 2:47 AM, an alert signaled trouble with the staging box running Ubuntu 24.04. The issue was uWSGI workers swapping due to excessive memory pressure, causing a 12-second GET request instead of a simple health check. The load average reached 8.4 on a 2-core instance with 8GB RAM, primarily due to an unnecessary dependency graph.
Inspecting the installed packages with `pip freeze` revealed 47 packages, despite the application's codebase being limited to three files. The culprit was Werkzeug 2.3.x, incompatible with Flask 3.0.3, which was pulled in from an outdated middleware package. Werkzeug's 2.x version is incompatible with Flask's 3.x API layer, leading to an import chain resolving to the wrong package. This mistake was only discovered after the OOM killer started writing to syslog.
Ubuntu 24.04 ships Python 3.12, but Flask 3.x requires Werkzeug 3.0, Jinja2, click, itsdangerous, blinker, and importlib-metadata. The official installation method, `apt install python3-flask`, installs a distro-pinned Werkzeug 2.x, causing routing issues under production load. The correct installation path involves explicitly setting Python 3.12, upgrading the resolver, creating a virtual environment, and installing Flask with specific version constraints.
This ensures the virtual environment remains isolated from system packages, preventing conflicts and ensuring proper functionality.
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