Add top-level Fastify error handler that logs full stack on 5xx (#312)#314
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Without this, 500 responses carried only the 91-byte Fastify default body and nothing hit stdout/pm2 — the #309 investigation had to infer the exception from the response-body size. Now every 5xx logs err.stack plus method/url/hostname via request.log.error. 4xx errors are unaffected. Response body shape is preserved (reply.send(err) delegates to Fastify's default serialization), so no existing consumer sees a behavior change.
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Pull request overview
Adds a centralized Fastify error handler so unhandled 5xx responses reliably emit stack traces (with request context) to logs, improving production debugging for intermittent internal errors (per #309/#312) without changing the existing error response body contract.
Changes:
- Introduces
registerErrorHandler(fastify)that logs fullerr.stack+ method/url/hostname for 5xx and delegates response serialization to Fastify. - Registers the new error handler during server creation (
createServer) so it applies globally. - Adds a focused test verifying 5xx logging/response shape and that 4xx errors do not trigger stack logging.
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
| test/error-handler.test.js | Adds coverage to ensure 5xx stack logging + request context and preserves Fastify default error body shape; verifies 4xx doesn’t trigger 5xx logging. |
| src/utils/error-handler.js | Implements the top-level Fastify setErrorHandler with conditional 5xx stack logging. |
| src/server.js | Wires the handler into server initialization so it runs for all routes/plugins. |
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Summary
Test plan
Fixes #312