[JENKINS-34979] Port allocation duplicate on "Concurrent builds"

When configuring a "Pooled TCP port", the pool assignment is not unique when the build is performed concurrently (see "Execute concurrent builds if necessary").

Never had an issue before and problem seems to be introduced after we updated to Jenkins 2.0.

Easy repro:

• create new job with "Pooled TCP port" and "Execute concurrent builds if necessary" options


• execute build multiple times


• see console output: same port is assigned multiple times

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Originally reported by ricktw, imported from: Port allocation duplicate on "Concurrent builds"

• assignee: andresrc
  
• status: Open
  
• priority: Major
  
• component(s): port-allocator-plugin
  
• resolution: Unresolved
  
• votes: 0
  
• watchers: 3
  
• imported: 20251216-225446
  

Raw content of original issue

When configuring a "Pooled TCP port", the pool assignment is not unique when the build is performed concurrently (see "Execute concurrent builds if necessary").


Never had an issue before and problem seems to be introduced after we updated to Jenkins 2.0.


Easy repro:



	
create new job with "Pooled TCP port" and "Execute concurrent builds if necessary" options

	
execute build multiple times

	
see console output: same port is assigned multiple times

environment

```
Jenkins Version: 2.5

OS: Ubuntu

Guess it is introduced in Jenkins 2.0?

Was there a rewrite in how plugins are loaded when running concurrent? Its own classloader?
```

Start by reproducing the pooled TCP port allocation with concurrent builds in the port-allocator-plugin, using the configuration and steps in the issue. Trace the pooled port handling and verify that repeated concurrent builds receive unique ports; done means the console output no longer shows duplicate assignments.

Written by the indexing model from the issue text.