HDDS-7917. EC: ECBlockInputStream should try spare replicas on error #4253
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adoroszlai
approved these changes
Feb 7, 2023
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| // Now make the spare one error on the next read and we should get an | ||
| // error with two failed locations | ||
| streamFactory.getBlockStreams().get(3).setThrowException(true); |
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Can you please explain where index 3 is derived from?
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Yea I will add a comment for this. Its the order the streams are created in the streamFactory. Indexes 1, 2 and 3 will be read, creating streams 0, 1, and 2. Then when we create another stream to read the new index 1 it will be stream 3.
hemantk-12
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to hemantk-12/ozone
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Feb 16, 2023
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What changes were proposed in this pull request?
In ECBlockInputStream, it is possible to have multiple locations for a single replicaIndex, if, say one replica is decommissioned but still online and there is also an IN_SERVICE replica.
Similar for Maintenance - there can be maintenance and in_service replicas, or just over replicated replicas.
As things stand, if a read to an index fails, it causes a failover to reconstruction read, but there are occassions where it would be possible to read from the spare replica and no need to fall back to reconstruction.
This PR allows spare replicas to be tried before giving up with an error.
What is the link to the Apache JIRA
https://issues.apache.org/jira/browse/HDDS-7917
How was this patch tested?
Added a new unit test.