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1. Refactor the log implementations by abstracting the log and log segment, allowing all managers like LogManager and LogCleaner to depend on the abstract log class instead of the specific UnifiedLog implementation.

2. Define a new abstraction to mask the differences between various shared storage services, called ' Stream. ' We will use Stream to implement a SharedLog that extends the AbstractLog. Just as a File API bridges the gap between LocalLog and a hard disk, Stream will bridge the gap between SharedLog and shared storage services like S3.

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1. AbstractLog and AbstractLogSegment are basic abstract classes containing common interfaces and logic methods for both bog file logs and shared logs.

2. All managers relying on UnifiedLog should be refactored to depend on AbstractLog.

3. UnifiedLog and LogSegment will implement AbstractLog and AbstractLogSegment. This is the core of the current classic storage engine.

4. A new log implementation, SharedLog and SharedLogSegment, will also depend on AbstractLog and AbstractLogSegment. We recommend using 'Stream' APIs for shared log implementation, which can then be applied to S3 or other storage services. However, 'Stream' is  is optional.

Optional Stream layer

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