[jira] [Commented] (HIVE-15908) OperationLog's LogFile writer should have autoFlush turned on

["Harsh J (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-15908?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15865281#comment-15865281 ] 

Harsh J commented on HIVE-15908:
--------------------------------

(H/T to Lingesh Radhakrishnan for the discovery)

> 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
>    Affects Versions: 0.13.0
>            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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