reverse-proxy/tasks/ops/body-size-limit.md

id, name, status, depends_on, scope, risk, impact, level

id	name	status	depends_on	scope	risk	impact	level
ops/body-size-limit	Implement global request body size limit with axum DefaultBodyLimit middleware	complete	config/dynamic-config	single	trivial	isolated	implementation

Description

Implement the global request body size limit using axum's DefaultBodyLimit middleware. The default limit is 100 MB (104,857,600 bytes), matching the current nginx configuration and accommodating Gitea's push operations with large pack files (ADR-018).

Implementation

• Set DefaultBodyLimit::max(body_limit_bytes) as axum middleware
• body_limit_bytes comes from DynamicConfig, so it can be changed at runtime via config reload
• When the limit is exceeded, axum returns 413 Payload Too Large with Payload Too Large body
• In Phase 1, the limit is global (not per-site)

Config Reload

Since body_limit_bytes is in DynamicConfig, it updates on config reload. However, axum's DefaultBodyLimit is typically set as a layer at router construction time. The implementation needs to ensure the current limit is read from DynamicConfig on each request, not cached at router construction time.

This may require a custom middleware that reads DynamicConfig via ArcSwap on each request, rather than relying solely on axum's DefaultBodyLimit.

Acceptance Criteria

• Body size limit enforced on all proxied requests
• Default: 100 MB (104,857,600 bytes)
• 413 Payload Too Large response when limit exceeded
• Limit is configurable via DynamicConfig
• Limit can be changed at runtime via config reload
• Config value is read from ArcSwap on each request (not cached)
• Integration test: request with body > limit receives 413
• Integration test: request with body < limit succeeds

References

• docs/architecture/proxy.md — body size limit section
• docs/architecture/config.md — DynamicConfig, body_limit_bytes
• docs/architecture/decisions/018-body-size-limit.md — 100 MB default rationale

Notes

The implementation agent should investigate whether axum's DefaultBodyLimit can be dynamically updated, or if a custom middleware reading from ArcSwap is needed. The important thing is that config reload changes the limit without restarting.

Summary

To be filled on completion