Lars Hofhansl created HBASE-11667:
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Summary: Simplify ClientScanner logic for NSREs.
Key: HBASE-11667
URL: https://issues.apache.org/jira/browse/HBASE-11667
Project: HBase
Issue Type: Improvement
Reporter: Lars Hofhansl
Assignee: Lars Hofhansl
Fix For: 0.99.0, 2.0.0, 0.94.23, 0.98.6
We ran into an issue with Phoenix where a RegionObserver coprocessor intercepts
a scan and returns an aggregate (in this case a count) with a fake row key. It
turns out this does not work when the {{ClientScanner}} encounters NSREs, as it
uses the last key it saw to reset the scanner to try again (which in this case
would be the fake key).
While this is arguably a rare case and one could also argue that a region
observer just shouldn't do this... While looking at {{ClientScanner}}'s code I
found this logic not necessary.
A NSRE occurred because we contacted a region server with a key that it no
longer hosts. This is the start key, so it is always correct to retry with this
same key. That simplifies the ClientScanner logic and also make this sort of
coprocessors possible,
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