Copilot commented on code in PR #13209: URL: https://github.com/apache/trafficserver/pull/13209#discussion_r3320863497
########## example/plugins/c-api/redo_cache_lookup/redo_cache_lookup.cc: ########## @@ -0,0 +1,91 @@ +/** @file + + An example plugin to redo cache lookups with a fallback URL. + + @section license License + + Licensed to the Apache Software Foundation (ASF) under one + or more contributor license agreements. See the NOTICE file + distributed with this work for additional information + regarding copyright ownership. The ASF licenses this file + to you under the Apache License, Version 2.0 (the + "License"); you may not use this file except in compliance + with the License. You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + + Unless required by applicable law or agreed to in writing, software + distributed under the License is distributed on an "AS IS" BASIS, + WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + See the License for the specific language governing permissions and + limitations under the License. + */ + +#include <string> +#include <string_view> + +#include "ts/ts.h" +#include "redo_cache_lookup_config.h" + +#define PLUGIN_NAME "redo_cache_lookup" + +namespace +{ +DbgCtl dbg_ctl{PLUGIN_NAME}; + +struct RedoCacheLookupConfig { + RedoCacheLookupConfig(std::string_view fallback) : fallback(fallback) {} + + std::string fallback; +}; + +int +handle_cache_lookup_complete(TSCont contp, TSEvent event, void *edata) +{ + if (event != TS_EVENT_HTTP_CACHE_LOOKUP_COMPLETE) { + return 0; + } + + TSHttpTxn txnp = static_cast<TSHttpTxn>(edata); + auto *config = static_cast<RedoCacheLookupConfig *>(TSContDataGet(contp)); + int status = TS_CACHE_LOOKUP_MISS; + + if (TSHttpTxnCacheLookupStatusGet(txnp, &status) != TS_SUCCESS || status == TS_CACHE_LOOKUP_MISS || + status == TS_CACHE_LOOKUP_SKIPPED) { + Dbg(dbg_ctl, "rewinding to check for fallback url: %s", config->fallback.c_str()); + TSHttpTxnRedoCacheLookup(txnp, config->fallback.c_str(), static_cast<int>(config->fallback.size())); + } + + TSHttpTxnReenable(txnp, TS_EVENT_HTTP_CONTINUE); + return 0; +} +} // namespace + +void +TSPluginInit(int argc, const char *argv[]) +{ + TSPluginRegistrationInfo info; + + Dbg(dbg_ctl, "Init"); + info.plugin_name = PLUGIN_NAME; + info.vendor_name = "Apache Software Foundation"; + info.support_email = "[email protected]"; + + if (TSPluginRegister(&info) != TS_SUCCESS) { + TSError("[%s] Plugin registration failed", PLUGIN_NAME); + return; + } + + auto fallback = redo_cache_lookup::parse_fallback_url(argc, argv); + + if (!fallback) { + Dbg(dbg_ctl, "Missing fallback option."); + TSError("[%s] Missing fallback option", PLUGIN_NAME); + return; + } + Dbg(dbg_ctl, "Initialized with fallback: %s", fallback->c_str()); + + TSCont contp = TSContCreate(handle_cache_lookup_complete, nullptr); + TSContDataSet(contp, new RedoCacheLookupConfig(*fallback)); Review Comment: `RedoCacheLookupConfig` is allocated with `new` and stored via `TSContDataSet()`, but it is never freed. Even though this is an example plugin, it’s easy to avoid the leak by storing the config in plugin-lifetime storage (e.g., a `static`/global `RedoCacheLookupConfig` or `std::unique_ptr` with a lifecycle shutdown hook) or by adding a cleanup hook that deletes the config on shutdown. ########## example/plugins/c-api/redo_cache_lookup/redo_cache_lookup.cc: ########## @@ -0,0 +1,91 @@ +/** @file + + An example plugin to redo cache lookups with a fallback URL. + + @section license License + + Licensed to the Apache Software Foundation (ASF) under one + or more contributor license agreements. See the NOTICE file + distributed with this work for additional information + regarding copyright ownership. The ASF licenses this file + to you under the Apache License, Version 2.0 (the + "License"); you may not use this file except in compliance + with the License. You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + + Unless required by applicable law or agreed to in writing, software + distributed under the License is distributed on an "AS IS" BASIS, + WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + See the License for the specific language governing permissions and + limitations under the License. + */ + +#include <string> +#include <string_view> + +#include "ts/ts.h" +#include "redo_cache_lookup_config.h" + +#define PLUGIN_NAME "redo_cache_lookup" + +namespace +{ +DbgCtl dbg_ctl{PLUGIN_NAME}; + +struct RedoCacheLookupConfig { + RedoCacheLookupConfig(std::string_view fallback) : fallback(fallback) {} + + std::string fallback; +}; + +int +handle_cache_lookup_complete(TSCont contp, TSEvent event, void *edata) +{ + if (event != TS_EVENT_HTTP_CACHE_LOOKUP_COMPLETE) { + return 0; + } + + TSHttpTxn txnp = static_cast<TSHttpTxn>(edata); + auto *config = static_cast<RedoCacheLookupConfig *>(TSContDataGet(contp)); + int status = TS_CACHE_LOOKUP_MISS; + + if (TSHttpTxnCacheLookupStatusGet(txnp, &status) != TS_SUCCESS || status == TS_CACHE_LOOKUP_MISS || + status == TS_CACHE_LOOKUP_SKIPPED) { + Dbg(dbg_ctl, "rewinding to check for fallback url: %s", config->fallback.c_str()); + TSHttpTxnRedoCacheLookup(txnp, config->fallback.c_str(), static_cast<int>(config->fallback.size())); + } Review Comment: `TSHttpTxnRedoCacheLookup()` rewinds the state machine and will lead to another `TS_EVENT_HTTP_CACHE_LOOKUP_COMPLETE` callback. As written, if the fallback URL also results in `TS_CACHE_LOOKUP_MISS`/`_SKIPPED`, this hook will call `TSHttpTxnRedoCacheLookup()` again with the same URL and can loop indefinitely for a transaction. Consider adding a per-transaction guard (e.g., reserve a `TS_USER_ARGS_TXN` index via `TSUserArgIndexReserve` and set a flag on first redo, or compare the current cache-lookup URL against the fallback and only redo when they differ). Also, check the return code from `TSHttpTxnRedoCacheLookup()` and avoid redoing when `TSHttpTxnCacheLookupStatusGet()` fails (treat that as an error rather than assuming MISS). -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
