Apache9 commented on a change in pull request #390: HBASE-22623 - Add
RegionObserver coprocessor hook for preWALAppend
URL: https://github.com/apache/hbase/pull/390#discussion_r311968129
##########
File path:
hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/RegionObserver.java
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@@ -1104,4 +1104,16 @@ default DeleteTracker postInstantiateDeleteTracker(
throws IOException {
return delTracker;
}
+
+ /**
+ * Called just before the WAL Entry is appended to the WAL. Implementing
this hook allows
+ * coprocessors to add extended attributes to the WALKey that then get
persisted to the
+ * WAL, and are available to replication endpoints to use in processing WAL
Entries.
+ * @param ctx the environment provided by the region server
+ * @param key the WALKey associated with a particular append to a WAL
+ */
+ default void preWALAppend(ObserverContext<RegionCoprocessorEnvironment> ctx,
WALKey key,
Review comment:
Phoenix already uses lots of deprecated methods in HBase, and I believe you
can not find alternate solutions, for example, this one
```
/**
* Called before creation of Reader for a store file.
* Calling {@link
org.apache.hadoop.hbase.coprocessor.ObserverContext#bypass()} has no
* effect in this hook.
*
* @param ctx the environment provided by the region server
* @param fs fileystem to read from
* @param p path to the file
* @param in {@link FSDataInputStreamWrapper}
* @param size Full size of the file
* @param cacheConf
* @param r original reference file. This will be not null only when
reading a split file.
* @param reader the base reader, if not {@code null}, from previous
RegionObserver in the chain
* @return a Reader instance to use instead of the base reader if
overriding
* default behavior, null otherwise
* @deprecated For Phoenix only, StoreFileReader is not a stable interface.
*/
@Deprecated
// Passing InterfaceAudience.Private args FSDataInputStreamWrapper,
CacheConfig and Reference.
// This is fine as the hook is deprecated any way.
default StoreFileReader
preStoreFileReaderOpen(ObserverContext<RegionCoprocessorEnvironment> ctx,
FileSystem fs, Path p, FSDataInputStreamWrapper in, long size,
CacheConfig cacheConf,
Reference r, StoreFileReader reader) throws IOException {
return reader;
}
```
You can add javadoc to say that now it is only supposed to be used in
Phoenix, but I still think we should mark it as deprecated, otherwise it will
be confusing that why in WALObserver, we say that WALEdit is private and should
not be used, but then in RegionObserver, we allow users to use it.
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