Example migration check: primary-only, never walk every pool - #8
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ActiveRecord::Migration.check_all_pending! iterates EVERY configured connection pool. In a Solid-Queue/Cache/Cable app the cache pool is hot on every request, so under load the check blocks on pool checkout and a healthy page drifts into check-timeout territory. Measured in production: 122ms idle, >10s under traffic — a false ❌ from the example everyone copies. The replacement checks the primary pool's migration context, read-only, ~7ms, and asks the question the tripwire actually means: did a deploy land with pending schema migrations. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Found live on licenseseat's /healthcheck within minutes of adding business checks: the example's
check_all_pending!walks every configured pool (queue/cache/cable), blocks on checkout under load, and times out a healthy page — 122ms idle vs >10s under traffic, measured in prod. Replacement is primary-onlymigration_context.needs_migration?(~7ms, read-only), which is also the question the check actually asks. Examples + README.