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https://issues.apache.org/jira/browse/ZOOKEEPER-4681?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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krystal he updated ZOOKEEPER-4681:
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Attachment: (was: zookeeper-divergence3.txt)
> 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: Critical
>
> 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. By adding relevant
> code to the zookeeper source code，my tool can drop the PROPOSAL, ACK and
> COMMIT messages and collect the values of some variables of each server at
> the end of each round. Except affecting message reception, my code will not
> affect other actions of Zookeeper.
>
> Setup:
> Replace directory called "zookeeper-server" in Zookeeper 3.5.8 with the
> "zookeeper-server" in [my github repo|https://github.com/kry4tall/CC-ZOO358].
> Ant the modified Zookeeper 3.5.8 to get zookeeper-3.5.8.jar. Replace
> zookeeper-3.5.8.jar downloaded by maven.
> Create a directory called "states" and a file called
> "[scenarios|https://github.com/kry4tall/CC-ZOO358/blob/krystal/zoo-tester/test/scenarios]";.
> Write the path to test.properties in zoo-tester's resource directory.
> Use "-s divergence-2" as the startup parameter to run the main method of
> ZooTester.
> OS: ubuntu 22.04.2.
>
> Base scenario:
> 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 followers.
> # (Optional) Read /key0 and /key1.
> # Request to set /key0 to 1001 on 3 servers.
> # (Optional) Read /key0 and /key1.
> Surprisingly, both requests worked，reading /key0 == 1000, /key1 == 1001 from
> C and /key0 == 0, /key1 == 1001 from A,B.
> However, value 1000 and 1001 should not appear in any znode, because the
> proposal of the first request cannot obtain enough ack, it cannot be
> committed. And servers will also not commit the proposal of the second
> request, because there is a pending proposal that has not been committed
> before, according to the source code of Zookeeper.
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