Zoltan Borok-Nagy has posted comments on this change. ( http://gerrit.cloudera.org:8080/24416 )
Change subject: IMPALA-15079: Cleanup Open/Close locking in SharedJdbcConnection ...................................................................... Patch Set 1: (2 comments) http://gerrit.cloudera.org:8080/#/c/24416/1/be/src/exec/data-source-scan-node.cc File be/src/exec/data-source-scan-node.cc: http://gerrit.cloudera.org:8080/#/c/24416/1/be/src/exec/data-source-scan-node.cc@126 PS1, Line 126: notify_all Since threads are contending for std::mutex, notify_one() could be called instead, since there will be exactly one winner anyway. Also, it should be called outside of the lock. http://gerrit.cloudera.org:8080/#/c/24416/1/be/src/exec/data-source-scan-node.cc@104 PS1, Line 104: { : std::unique_lock<std::mutex> lk(lock_); : ++ref_count_; : if (ref_count_ > 1) { : // Subsequent callers: wait for the first caller to finish, then reuse. : open_cv_.wait(lk, [this] { return open_done_; }); : result->__set_scan_handle(scan_handle_); : return open_status_; : } : } : : // First caller: initialize the executor and open the Java data source outside the lock. : // All N C++ scanner threads share this single connection. : Status s = executor_.Init(jar_path, class_name, api_version, init_string); : if (s.ok()) s = executor_.Open(params, result); : if (s.ok()) s = Status(result->status); : : { : std::unique_lock<std::mutex> lk(lock_); : if (s.ok()) scan_handle_ = result->scan_handle; : open_status_ = s; : open_done_ = true; : open_cv_.notify_all(); : } > I can remove it and in this case it shouldn't matter, but generally I think I think the simpler the better. std::mutex is completely fine to wait on slow things. I think condition_variable just adds complexity for this simple case. Probably the biggest problem is that if executor.Open() hangs indefinitely, then these threads hang forever. But it's probably true to a lot places thoughout the Impala code. -- To view, visit http://gerrit.cloudera.org:8080/24416 To unsubscribe, visit http://gerrit.cloudera.org:8080/settings Gerrit-Project: Impala-ASF Gerrit-Branch: master Gerrit-MessageType: comment Gerrit-Change-Id: Ic9f5c4ac71031b74b51bfa27ed04be10ed92e222 Gerrit-Change-Number: 24416 Gerrit-PatchSet: 1 Gerrit-Owner: Csaba Ringhofer <[email protected]> Gerrit-Reviewer: Csaba Ringhofer <[email protected]> Gerrit-Reviewer: Impala Public Jenkins <[email protected]> Gerrit-Reviewer: Noemi Pap-Takacs <[email protected]> Gerrit-Reviewer: Pranav Lodha <[email protected]> Gerrit-Reviewer: Zoltan Borok-Nagy <[email protected]> Gerrit-Comment-Date: Thu, 18 Jun 2026 14:39:17 +0000 Gerrit-HasComments: Yes
