Michael Smith has posted comments on this change. ( http://gerrit.cloudera.org:8080/21803 )
Change subject: IMPALA-915: Support cancel queries in frontend ...................................................................... Patch Set 42: (1 comment) http://gerrit.cloudera.org:8080/#/c/21803/41/fe/src/main/java/org/apache/impala/service/Canceller.java File fe/src/main/java/org/apache/impala/service/Canceller.java: http://gerrit.cloudera.org:8080/#/c/21803/41/fe/src/main/java/org/apache/impala/service/Canceller.java@94 PS41, Line 94: public static void cancel(TUniqueId queryId) { > What happens if a query is cancelled twice with the second cancel coming in I think: 1. cancelledThreads_.add may be called twice; it either ignores the 2nd add because it's already present, or adds it back 2. queryThread.interrupt() is called twice; this should be fine, interrupt either halts a system call or sets the interrupt flag on the thread, so the 2nd call will do nothing If the 2nd cancel reaches queryThreads_.containsKey before unregister, it will do nothing else. Unregister will then remove the key from cancelledThreads_. If the 2nd cancel reaches queryThreads_.containsKey during unregister, we'll get two calls to cancelledThreads_.remove, which is fine, 2nd one is a noop. If the 2nd cancel reaches queryThreads_.containsKey after unregister, it will call cancelledThreads_.remove, which either cleans up its earlier add or is a noop. So: 1. cancelledThreads_.add is basically idempotent; either unregister or cancel will clean it up later. 2. queryThread.interrupt is idempotent, we can call it multiple times without an issue. 3. cancelledThreads_.remove is idempotent; it either removes the queryThread or is a noop. I can add a test where multiple cancels are sent at the same time. -- To view, visit http://gerrit.cloudera.org:8080/21803 To unsubscribe, visit http://gerrit.cloudera.org:8080/settings Gerrit-Project: Impala-ASF Gerrit-Branch: master Gerrit-MessageType: comment Gerrit-Change-Id: I0d25d4c7fb0b8dcc7dad9510db1e8dca220eeb86 Gerrit-Change-Number: 21803 Gerrit-PatchSet: 42 Gerrit-Owner: Michael Smith <michael.sm...@cloudera.com> Gerrit-Reviewer: Andrew Sherman <asher...@cloudera.com> Gerrit-Reviewer: Impala Public Jenkins <impala-public-jenk...@cloudera.com> Gerrit-Reviewer: Jason Fehr <jf...@cloudera.com> Gerrit-Reviewer: Joe McDonnell <joemcdonn...@cloudera.com> Gerrit-Reviewer: Michael Smith <michael.sm...@cloudera.com> Gerrit-Reviewer: Quanlong Huang <huangquanl...@gmail.com> Gerrit-Reviewer: Riza Suminto <riza.sumi...@cloudera.com> Gerrit-Comment-Date: Thu, 17 Apr 2025 21:49:21 +0000 Gerrit-HasComments: Yes
