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Functions runtime lifecycle

Rule ID: check_functions_runtime_lifecycle · Category: configuration · Section: runtime Severity: error (gating) on v1/v2/v3 · Profiles: deploy, full · Tier: core

What it checks

The Azure Functions runtime major version (FUNCTIONS_EXTENSION_VERSION) for a Python app:

Runtime Verdict
v1 Incompatible with Python — fails outright
v2 / v3 Out of support — fails
v3 on Linux Consumption Out of support and stops running on a published date — emphasized failure
v4 Current GA runtime — passes
Undeterminable Skips

The runtime is resolved from infra config / app settings via the deploy-config ingestion pipeline; lifecycle dates come from the version-controlled compatibility catalog.

Why it matters

Running on a legacy or out-of-support Azure Functions runtime loses security updates and eventually the ability to run; runtime v1 cannot host a Python app at all.

Symptoms

Host fails to start on an unsupported runtime; v3 Linux Consumption apps stop running after the published date; v1 rejects Python apps outright.

Example finding

Azure Functions runtime v3 is out of support; migrate to runtime v4.

How to fix

Target the v4 Azure Functions runtime (FUNCTIONS_EXTENSION_VERSION=~4). The v1/v2/v3 runtimes are legacy or out of support; v1 does not support Python at all.

Reference