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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: zookeeper-no-drop.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: Critical
> Attachments: zookeeper-no-drop.patch, zookeeper-scenario1.patch,
> zookeeper-scenario2.patch, zookeeper-scenario3.patch,
> zookeeper-scenario4.patch, zookeeper-scenario5.patch,
> zookeeper-scenario6.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. 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
> instance at the end of each round. Except affecting message reception, my
> code will not affect other actions of Zookeeper.
>
> Setup:
> ubuntu 22.04.2, maven 3.9.0, ant 1.10.13.
> 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" or "-s divergence-X"(X = 2,3,4,5,6) as the startup
> parameter to run the main method of ZooTester.
>
> 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) Stop all servers and then restart them.
> # (Optional) Read /key0 and /key1 in all servers respectively.
> # Request to set /key0 to 1001 on 3 servers.
> # (Optional) Stop all servers and then restart them.
> # Read /key0 and /key1 in all servers respectively.
> Mark the execution step list [1,2,4,5,7] as scenario1, [1,2,3,4,5,7] as
> scenario2, [1,2,4,5,6,7] as scenario3, [1,2,3,4,5,6,7] as scenario4,
> [1,2,5,7] as scenario5 and [1,2,5,6,7] as scenario6.
> The output of these 6 scenarios is placed in the attachment. Surprisingly,
> key0 is set to 1000 and key1 is set to 1001 in some scenarios and restarting
> all servers affects the value of znodes. For comparison, I also put the
> output without losing the ack message in the attachment. Everything is fine
> when no ack is dropped.
> 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. From the values of the variables of the server instance I
> collected, it is true that the proposal of the first request was uncommitted.
> And servers will also not commit the proposal of the second request if there
> is a pending proposal that has not been committed before, according to the
> source code of Zookeeper.
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