EnricoMi opened a new issue, #1433:
URL: https://github.com/apache/incubator-uniffle/issues/1433

   ### Code of Conduct
   
   - [X] I agree to follow this project's [Code of 
Conduct](https://www.apache.org/foundation/policies/conduct)
   
   
   ### Search before asking
   
   - [X] I have searched in the 
[issues](https://github.com/apache/incubator-uniffle/issues?q=is%3Aissue) and 
found no similar issues.
   
   
   ### Describe the bug
   
   The ShuffleServer state transitions are subject to race conditions. In 
unlikely but possible situations, states can transition undesirably, e.g.
   - `DECOMMISSIONING` -> `UNHEALTHY` -> `ACTIVE` (though still unhealthy)
   - `DECOMMISSIONING` -> `UNHEALTHY` (decommissioning stopped)
   - `ACTIVE` -> any non-`ACTIVE` -> `DECOMMISSIONING` (not allowed by code)
   
   Example:
   ```Java
   if (!ServerStatus.ACTIVE.equals(serverStatus.get())) {
     throw new InvalidRequestException(
         "Shuffle Server is processing other procedures, current status:" + 
serverStatus);
   }
   serverStatus.set(ServerStatus.DECOMMISSIONING);
   ```
   Just before line `serverStatus.set(ServerStatus.DECOMMISSIONING);`, the 
state could change, so it is not guaranteed that `ACTIVE` state turns into 
`DECOMMISSIONING`.
   
   Having an `AtomicReference<ServerStatus>`, this should look like:
   ```Java
   boolean wasActive = serverStatus.compareAndSet(ServerStatus.ACTIVE, 
ServerStatus.DECOMMISSIONING);
   if (!wasActive) {
     throw new InvalidRequestException(
         "Shuffle Server is processing other procedures, current status:" + 
serverStatus);
   }
   ```
   
   Ideally, you would use `compareAndExchange`, so that the state in the 
exception is accurate (that could change in the meantime as well), but I get 
such a warning for that: `Usage of API documented as @since 1.9+`:
   ```Java
   ServerStatus before = serverStatus.compareAndExchange(ServerStatus.ACTIVE, 
ServerStatus.DECOMMISSIONING);
   if (!ServerStatus.ACTIVE.equals(before)) {
     throw new InvalidRequestException(
             "Shuffle Server is processing other procedures, current status:" + 
before);
   }
   ```
   
   ### Affects Version(s)
   
   master
   
   ### Uniffle Server Log Output
   
   _No response_
   
   ### Uniffle Engine Log Output
   
   _No response_
   
   ### Uniffle Server Configurations
   
   _No response_
   
   ### Uniffle Engine Configurations
   
   _No response_
   
   ### Additional context
   
   _No response_
   
   ### Are you willing to submit PR?
   
   - [X] Yes I am willing to submit a PR!


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