...
- If the only server that saves a copy of this segment is destroyed and at the same time the other replicas are unable to catch up, then we may completely lose this segment. In this case, we need to do a segment recovery (either from Kafka or from an offline source). One way to get around this is to upload the segment to the controller as it happens in the current protocol and expose this segment via some HTTP URL. This gives additional redundancy without drastically changing the protocol.
b) Quorum:
We can further improve the availability of this design by requiring the controller to wait for a quorum of servers to finish ingesting the current segment before updating segment metadata and transitioning on an ONLINE state. In this case, the Segment metadata (segment location) will point to a list of HTTP endpoints (for the different replicas that successfully ingested this segment).
...