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  1. What happens when the segment upload fails but the preceding metadata commit succeeds ?
    • In this case, if a server needs to download the segment, it needs to download from the commit server which has a copy of the data.
    • We in fact If users want to minimize the chances of downloading from peer servers: so the segment completion mode should can be set as DEFAULT instead of DOWNLOAD.
    • In the background, RealtimeValidationManager will fix the upload failure by periodically asks the server to upload missing segments.
  2. What happens if another server gets a "download" but the committer has not gotten to ONLINE state yet?  
    • To account for the fact that the metadata commit happens before the segment upload, another server should do retries (with exponential backoff) when downloading.
    • The retries with wait can greatly reduce the issues caused by the above race condition.

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