steveloughran commented on a change in pull request #2801:
URL: https://github.com/apache/hadoop/pull/2801#discussion_r618655930
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File path:
hadoop-tools/hadoop-aws/src/site/markdown/tools/hadoop-aws/troubleshooting_s3a.md
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@@ -1036,6 +1036,39 @@
This includes resilient logging, HBase-style journaling
and the like. The standard strategy here is to save to HDFS and then copy to
S3.
+### <a name="syncable"></a> `UnsupportedOperationException` "S3A streams are
not Syncable. See HADOOP-17597."
+
+The application has tried to call either the `Syncable.hsync()` or
`Syncable.hflush()`
+methods on an S3A output stream. This has been rejected because the
+connector isn't saving any data at all. The `Syncable` API, especially the
+`hsync()` call, are critical for applications such as HBase to safely
+persist data.
+
+The S3A connector throws an `UnsupportedOperationException` when these API
calls
+are made, because the guarantees absolutely cannot be met: nothing is being
flushed
+or saved.
+
+* Applications which intend to invoke the Syncable APIs call
`hasCapability("hsync")` on
+ the stream to see if they are supported.
+* Or catch and downgrade `UnsupportedOperationException`.
+
+These recommendations _apply to all filesystems_.
+
+To downgrade the S3A connector to simplying warning of the use of
Review comment:
fixed
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