[PR] CAMEL-23945: Fix producer race on shared agent field (backport to 4.18.x) [camel]

["gnodet (via GitHub)" <gi...@apache.org>]

gnodet opened a new pull request, #25063:
URL: https://github.com/apache/camel/pull/25063

   _Claude Code on behalf of gnodet_
   
   ## Summary
   
   Backport of the fix for CAMEL-23945 to the `camel-4.18.x` branch.
   
   On `main`, the race condition in `LangChain4jAgentProducer.process()` was inadvertently fixed by commit `03d8361bbb7` (CAMEL-23697), which refactored the method to use a local variable. On `camel-4.18.x`, the original race still exists: `agentFactory.createAgent(exchange)` writes to the shared `this.agent` instance field, so concurrent exchanges can see each other's agents.
   
   ### The race (before this PR)
   ```java
   if (agentFactory != null) {
       agent = agentFactory.createAgent(exchange);  // writes to shared field
   }
   AiAgentBody<?> aiAgentBody = agent.processBody(messagePayload, exchange);
   ```
   
   Between the write and the read, another thread can overwrite `this.agent` with a different exchange's agent, causing the first exchange to use the wrong agent.
   
   ### The fix
   ```java
   Agent agent = agentFactory != null ? agentFactory.createAgent(exchange) : this.agent;
   AiAgentBody<?> aiAgentBody = agent.processBody(messagePayload, exchange);
   ```
   
   A method-local variable ensures each exchange uses only its own factory-created agent.
   
   ### Changes
   - **`LangChain4jAgentProducer.java`**: Changed `process()` to use a local `Agent agent` variable instead of writing to the shared instance field
   - **`LangChain4jAgentProducerConcurrencyTest.java`**: Added regression test that sends 50 concurrent exchanges through a single producer endpoint, each with a distinct factory-created agent. Verifies that every exchange receives the response from its own agent, not from another exchange's agent.
   
   ## Test plan
   - [x] New `LangChain4jAgentProducerConcurrencyTest` passes (1 test)
   - [x] All existing unit tests in the module pass (7 total)
   - [ ] CI green
   
   🤖 Generated with [Claude Code](https://claude.com/claude-code)


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Re: [PR] CAMEL-23945: Fix producer race on shared agent field (backport to 4.18.x) [camel]

["davsclaus (via GitHub)" <gi...@apache.org>]

davsclaus merged PR #25063:
URL: https://github.com/apache/camel/pull/25063


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