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HBASE-20349 [DOC] upgrade guide should call out removal of prefix-tree data block encoding

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Michael Stack 2018-04-11 15:07:27 -07:00
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4
src/main/asciidoc/_chapters/troubleshooting.adoc
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@ -102,9 +102,9 @@ To disable, set the logging level back to `INFO` level.
=== JVM Garbage Collection Logs
[NOTE]
----
====
All example Garbage Collection logs in this section are based on Java 8 output. The introduction of Unified Logging in Java 9 and newer will result in very different looking logs.
----
====
HBase is memory intensive, and using the default GC you can see long pauses in all threads including the _Juliet Pause_ aka "GC of Death". To help debug this or confirm this is happening GC logging can be turned on in the Java virtual machine.

11
src/main/asciidoc/_chapters/upgrading.adoc
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@ -409,6 +409,17 @@ A brief summary of related changes:
The Distributed Log Replay feature was broken and has been removed from HBase 2.y+. As a consequence all related configs, metrics, RPC fields, and logging have also been removed. Note that this feature was found to be unreliable in the run up to HBase 1.0, defaulted to being unused, and was effectively removed in HBase 1.2.0 when we started ignoring the config that turns it on (link:https://issues.apache.org/jira/browse/HBASE-14465[HBASE-14465]). If you are currently using the feature, be sure to perform a clean shutdown, ensure all DLR work is complete, and disable the feature prior to upgrading.
[[upgrade2.0.prefix-tree.removed]]
._prefix-tree_ encoding removed
The prefix-tree encoding was removed from HBase 2.0.0 (link:https://issues.apache.org/jira/browse/HBASE-19179[HBASE-19179]).
It was (late!) deprecated in hbase-1.2.7, hbase-1.4.0, and hbase-1.3.2.
This feature was removed because it as not being actively maintained. If interested in reviving this
sweet facility which improved random read latencies at the expensive of slowed writes,
write the HBase developers list at _dev at hbase dot apache dot org_.
[[upgrade2.0.metrics]]
.Changed metrics