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https://issues.apache.org/jira/browse/HIVE-15908?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Harsh J updated HIVE-15908:
---------------------------
Attachment: HIVE-15908.000.patch
> OperationLog's LogFile writer should have autoFlush turned on
> -------------------------------------------------------------
>
> Key: HIVE-15908
> URL: https://issues.apache.org/jira/browse/HIVE-15908
> Project: Hive
> Issue Type: Improvement
> Components: HiveServer2
> Reporter: Harsh J
> Assignee: Harsh J
> Priority: Minor
> Attachments: HIVE-15908.000.patch
>
>
> The HS2 offers an API to fetch Operation Log results from the maintained
> OperationLog file. The reader used inside class OperationLog$LogFile class
> reads line-by-line on its input stream, for any lines available from the OS's
> file input perspective.
> The writer inside the same class uses PrintStream to write to the file in
> parallel. However, the PrintStream constructor used sets PrintStream's
> {{autoFlush}} feature in an OFF state. This causes the BufferedWriter used by
> PrintStream to accumulate 8k worth of bytes in memory as the buffer before
> flushing the writes to disk, causing a slowness in the logs streamed back to
> the client. Every line must be ideally flushed entirely as-its-written, for a
> smoother experience.
> I suggest changing the line inside {{OperationLog$LogFile}} that appears as
> below:
> {code}
> out = new PrintStream(new FileOutputStream(file));
> {code}
> Into:
> {code}
> out = new PrintStream(new FileOutputStream(file), true);
> {code}
> This will cause it to use the described autoFlush feature of PrintStream and
> make for a better reader-log-results-streaming experience:
> https://docs.oracle.com/javase/7/docs/api/java/io/PrintStream.html#PrintStream(java.io.OutputStream,%20boolean)
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