Implement RFC 9213 Targeted HTTP Cache Control #12679
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Pull Request Overview
This PR implements RFC 9213 Targeted HTTP Cache Control, allowing cache directives to be targeted at specific caches through custom headers (e.g., CDN-Cache-Control). When configured, these targeted headers take precedence over standard Cache-Control for caching decisions, while still being passed through to downstream caches.
Key changes:
- Added configurable, priority-ordered list of targeted cache control headers via
proxy.config.http.cache.targeted_cache_control_headers - Modified cache control parsing logic to check targeted headers first before falling back to standard Cache-Control
- Made configuration overridable per-remap rule for flexible deployment scenarios
Reviewed Changes
Copilot reviewed 18 out of 18 changed files in this pull request and generated 1 comment.
Show a summary per file
| File | Description |
|---|---|
src/proxy/hdrs/MIME.cc |
Core cache control parsing logic updated to check targeted headers in priority order |
src/proxy/http/HttpSM.cc |
Integration point where targeted headers config is passed to cache control recomputation |
include/proxy/hdrs/MIME.h |
Added flag to track if cache control came from targeted header; updated signature |
src/records/RecordsConfig.cc |
Added new configuration record for targeted headers |
src/proxy/http/HttpConfig.cc |
Config initialization and reconfiguration handling with proper memory management |
include/proxy/http/HttpConfig.h |
Added char* field for targeted headers config |
src/shared/overridable_txn_vars.cc |
Made config overridable for per-transaction use |
src/api/InkAPI.cc |
API support for reading/writing targeted headers config; added char** converter |
src/api/InkAPITest.cc |
Added new config key to API test list |
plugins/lua/ts_lua_http_config.cc |
Added Lua plugin support for the new config |
include/ts/apidefs.h.in |
Added enum value for new config key |
tests/gold_tests/cache/targeted-cache-control.test.py |
Test harness for RFC 9213 functionality |
tests/gold_tests/cache/replay/targeted-cache-control.replay.yaml |
Comprehensive test scenarios covering priority, fallback, and per-remap override |
doc/admin-guide/files/records.yaml.en.rst |
Configuration reference documentation |
doc/admin-guide/configuration/cache-basics.en.rst |
User guide with examples and use cases |
doc/developer-guide/api/types/TSOverridableConfigKey.en.rst |
API enum documentation |
doc/developer-guide/api/functions/TSHttpOverridableConfig.en.rst |
API function documentation |
doc/admin-guide/plugins/lua.en.rst |
Lua plugin constant documentation |
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bneradt
commented
Nov 20, 2025
Comment on lines
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| field = nullptr; | ||
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| // Check for targeted cache control headers first (in priority order). | ||
| if (targeted_headers_str && *targeted_headers_str) { | ||
| swoc::TextView config_view{targeted_headers_str}; | ||
| while (config_view) { | ||
| swoc::TextView header_name = config_view.take_prefix_at(',').trim_if(&isspace); | ||
| if (!header_name.empty()) { | ||
| field = mime_hdr_field_find(this, std::string_view{header_name.data(), header_name.size()}); | ||
| if (field) { | ||
| // Found a targeted header! Mark it and stop searching. | ||
| m_cooked_stuff.m_cache_control.m_from_targeted_header = true; | ||
| break; | ||
| } | ||
| } | ||
| } | ||
| } | ||
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| // If no targeted header was found, fall back to standard Cache-Control. | ||
| if (!field) { | ||
| field = mime_hdr_field_find(this, static_cast<std::string_view>(MIME_FIELD_CACHE_CONTROL)); | ||
| } |
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This is the actualy interesting production change (part 1).
bneradt
commented
Nov 20, 2025
Comment on lines
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| // Recompute cooked cache control with targeted headers (pass nullptr if not configured). | ||
| const char *targeted_headers = | ||
| (t_state.txn_conf->targeted_cache_control_headers && t_state.txn_conf->targeted_cache_control_headers[0] != '\0') ? | ||
| t_state.txn_conf->targeted_cache_control_headers : | ||
| nullptr; | ||
| t_state.hdr_info.server_response.m_mime->recompute_cooked_stuff(nullptr, targeted_headers); | ||
|
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Contributor
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This is the other interesting production change (part 2).
This is "recooked" here to avoid intermingling the targeted cache control configuration into the MIME/parser interface. The recompute should be cheap, so I think this is OK. But if wanted, I can look into trying to get the parse to happen initially at parse_resp.
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This adds support for targeted Cache-Control headers (like CDN-Cache-Control) that allow cache directives to be targeted at specific caches. The implementation includes a configurable, priority-ordered list of targeted headers via proxy.config.http.cache.targeted_cache_control_headers, which is overridable per-remap rule. When a targeted header is present, it takes precedence over the standard Cache-Control header for caching decisions. Targeted headers are passed through downstream to allow proper cache hierarchy behavior. Fixes: apache#9113
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This adds support for targeted Cache-Control headers (like CDN-Cache-Control) that allow cache directives to be targeted at specific caches. The implementation includes a configurable, priority-ordered list of targeted headers via proxy.config.http.cache.targeted_cache_control_headers, which is overridable per-remap rule. When a targeted header is present, it takes precedence over the standard Cache-Control header for caching decisions. Targeted headers are passed through downstream to allow proper cache hierarchy behavior.
Fixes: #9113