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Add a new Size Limits section specifying that Cloud Controller must enforce a configurable maximum size (default: 1 KB) for route options to prevent excessive NATS bandwidth consumption. - Default limit: 1024 bytes - Configurable via cc.max_route_options_size BOSH property - CC returns HTTP 422 when limit is exceeded - Documents relationship with route emit interval for tuning This addresses feedback from the App-to-App mTLS RFC (PR #1438) where concerns were raised about NATS bandwidth impact of per-route options.
maxmoehl
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Mar 6, 2026
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Thanks for preparing this amendment. I like it overall, just 1.5 small comments.
Co-authored-by: Maximilian Moehl <44866320+maxmoehl@users.noreply.github.com>
- Remove duplicate 'Operator guidance' line from suggestion merge - Change 'bandwidth usage' to 'resource usage' for consistency - Add note that lowering size limit doesn't affect existing routes
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Summary
Adds a Size Limits section to RFC-0027 (Generic Per-Route Features) specifying that Cloud Controller must enforce a configurable maximum size for route options.
Changes
cc.max_route_options_sizeBOSH propertyContext
This addresses feedback from the App-to-App mTLS RFC (PR #1438) where @maxmoehl raised concerns about NATS bandwidth impact of per-route options. The discussion concluded that a global size limit enforced at the Cloud Controller level (with immediate user feedback) is the appropriate solution.
Rationale
Route registration messages are transmitted via NATS at a configurable interval from each app instance to each GoRouter instance. Large route options can significantly impact NATS bandwidth in deployments with many app instances. A 1 KB default accommodates most use cases (e.g., ~25 app GUIDs in an mTLS allowlist) while protecting platform stability.
cc @maxmoehl