[jira] [Created] (KAFKA-13971) Atomicity violations caused by improper usage of ConcurrentHashMap

["Divij Vaidya (Jira)" <ji...@apache.org>]

Divij Vaidya created KAFKA-13971:
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             Summary: Atomicity violations caused by improper usage of ConcurrentHashMap
                 Key: KAFKA-13971
                 URL: https://issues.apache.org/jira/browse/KAFKA-13971
             Project: Kafka
          Issue Type: Bug
            Reporter: Divij Vaidya


*Code:* [https://github.com/apache/kafka/blob/trunk/connect/runtime/src/main/java/org/apache/kafka/connect/runtime/WorkerConfigTransformer.java#L81-L84] 

*Problem*
We are using a {{{}ConcurrentHashMap{}}}, but usage of {{{}get(){}}}, {{null}} check, and {{put()}} may not be thread-safe at lines: 81, 82, and 84. Two threads can perform this same check at the same time and one thread can overwrite the value written by the other thread.

*Fix*
Consider replacing {{put()}} with {{putIfAbsent()}} to help prevent accidental overwriting. {{putIfAbsent()}} puts the value only if the {{ConcurrentHashMap}} does not contain the key and therefore avoids overwriting the value written there by the other thread's {{{}putIfAbsent(){}}}.



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