After sleeping on this, I now wonder whether this preconverted object can be extended further to cache these results internally, in the ATS core. Then the users of the API wouldn't need this interface to manually manage this object themselves. I plan to spend some time today investigating this.
On Thu, Dec 4, 2025 at 10:59 PM Brian Neradt <[email protected]> wrote: > Hi [email protected], > > I'd like to propose a new public API to address a performance issue > identified in GitHub issue #12292: > https://github.com/apache/trafficserver/issues/12292 > > > *The Problem*Some overridable string configurations require parsing > before they can be applied to a transaction. For example, > proxy.config.hostdb.ip_resolve needs to parse a string like "ipv4;ipv6" > into a host resolution preference order, and > proxy.config.http.negative_caching_list needs to parse "204 305 403" into a > status code bitset. > > Currently, when plugins like conf_remap use TSHttpTxnConfigStringSet() to > apply these configurations, the parsing happens on every request. For > high-traffic deployments applying the same configuration value repeatedly, > this is expensive. > > > *Proposed Solution*Add three new functions to ts.h that allow plugins to > pre-convert string values once at load time: > > // Pre-convert a string value (or nullptr for NULL/unset). > TSReturnCode TSConfigStringPreconvert(TSOverridableConfigKey conf, const > char *value, int length, TSPreconvertedConfigValue *result); > > // Apply the pre-converted value to a transaction. > TSReturnCode TSHttpTxnConfigPreconvertedValueSet(TSHttpTxn txnp, > TSOverridableConfigKey conf, TSPreconvertedConfigValue value); > > // Free the pre-converted value. > void TSPreconvertedConfigValueDestroy(TSPreconvertedConfigValue value); > > The TSPreconvertedConfigValue is an opaque handle that stores either the > pre-parsed representation (for configs that need special parsing) or the > original string (for configs that don't). > Passing nullptr as the value represents a NULL/unset configuration, which > is distinct from an empty string. > > > *Example Usage* > > // At plugin initialization (called once). > TSPreconvertedConfigValue g_preconverted = nullptr; > > TSReturnCode > TSRemapNewInstance(int argc, char* argv[], void** ih, ...) > { > TSConfigStringPreconvert( > TS_CONFIG_HTTP_NEGATIVE_CACHING_LIST, > "400 404 500", > -1, // The implementation will use strlen on the above string. > &g_preconverted); > return TS_SUCCESS; > } > > // At remap time (called on every matching request). > TSRemapStatus > TSRemapDoRemap(void* ih, TSHttpTxn rh, TSRemapRequestInfo* rri) > { > // Pass the preconverted value - no string parsing needed > // for each transaction. > TSHttpTxnConfigPreconvertedValueSet( > rh, > TS_CONFIG_HTTP_NEGATIVE_CACHING_LIST, > g_preconverted); > return TSREMAP_NO_REMAP; > } > > // At plugin destruction (called once). > void > TSRemapDeleteInstance(void* ih) > { > TSPreconvertedConfigValueDestroy(g_preconverted); > } > > For more details, see the following draft PR: > https://github.com/apache/trafficserver/pull/12734 > > Please let me know if you have any concerns. > > Thanks, > Brian Neradt > > -- > "Come to Me, all who are weary and heavy-laden, and I will > give you rest. Take My yoke upon you and learn from Me, for > I am gentle and humble in heart, and you will find rest for > your souls. For My yoke is easy and My burden is light." > > ~ Matthew 11:28-30 > -- "Come to Me, all who are weary and heavy-laden, and I will give you rest. Take My yoke upon you and learn from Me, for I am gentle and humble in heart, and you will find rest for your souls. For My yoke is easy and My burden is light." ~ Matthew 11:28-30
