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exactly_once_semantics

ABSTRACT

In the context of stream-processing, it Means that

Definition​

  • Each piece of data (event) in a stream is processed exactly one time even in the presence of failures like node crashes or network interruptions
  • Ensures that the state of the application and the results are correct, consistent, and not duplicated or lost.

Why Exactly-Once Semantics Matters​

  1. Correctness:

    • In applications like financial transactions, order processing, or user analytics, processing data multiple times or losing data can lead to incorrect results.
    • For example, counting a purchase twice or missing a user action could have significant consequences.

  2. Fault Tolerance:

    • Stream processing systems like Flink operate in distributed environments, where failures (e.g., machine crashes, network issues) are common. Exactly-once semantics ensures consistency even in such scenarios.

References