[ https://issues.apache.org/jira/browse/ZOOKEEPER-4681?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
krystal he updated ZOOKEEPER-4681: ---------------------------------- Attachment: restart-all-server.patch > Uncommitted requests have been executed > ---------------------------------------- > > Key: ZOOKEEPER-4681 > URL: https://issues.apache.org/jira/browse/ZOOKEEPER-4681 > Project: ZooKeeper > Issue Type: Bug > Components: quorum > Affects Versions: 3.5.8 > Reporter: krystal he > Priority: Major > Attachments: no-restart.patch, restart-all-server.patch > > > Using a [tool|https://github.com/kry4tall/CC-ZOO358] that I modifyed from > [Filip Niksic's zootester|https://github.com/fniksic/zootester] for testing > ZooKeeper, I discovered the following scenario which causes uncommitted > requests to be executed. > Zab protocol has three rounds: PROPOSE, ACK, and COMMIT. My tool can isolate > the PROPOSAL, ACK and COMMIT messages and collect the values of some > variables of each server at the end of each round. > Initially, start an ensemble with 3 servers called A, B, and C, and > initialize 2 znodes called /key0 and /key1, and set them to 0 and 1 > respectively. > # Request to set /key0 to 1000 on 3 servers. > # Isolate the ack messages of 2 servers. > # Request to set /key0 to 1001 on 3 servers. > # Stop all servers and restart them. > # Check the contents of /key0 and /key1. Surprisingly, both requests > worked,reading /key0 == 1000, /key1 == 1001. > If we skip step 4, we can read "/key0 == null, /key1 == null" from A and B, > and read "/key0 == 0, /key1 == 1001" from C. Value null is because the > "ConnectionLoss" with znodes. > However, 1000 and 1001 should not appear in any znode, because the first > proposal cannot obtain enough ack, it cannot be committed. According to the > source code of Zookeeper, the server will not commit the proposal of the > second request, because there is a proposal that has not been committed > before. -- This message was sent by Atlassian Jira (v8.20.10#820010)