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From "Harsh J (JIRA)" <>
Subject [jira] [Updated] (HIVE-15908) OperationLog's LogFile writer should have autoFlush turned on
Date Tue, 14 Feb 2017 07:28:41 GMT


Harsh J updated HIVE-15908:
    Status: Patch Available  (was: Open)

> OperationLog's LogFile writer should have autoFlush turned on
> -------------------------------------------------------------
>                 Key: HIVE-15908
>                 URL:
>             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$LogFile class reads line-by-line on its input
stream, for any lines available from the OS's file input perspective.
> The writer inside the same class uses PrintStream to write to the file in parallel. However,
the PrintStream constructor used sets PrintStream's {{autoFlush}} feature in an OFF state.
This causes the BufferedWriter used by PrintStream to accumulate 8k worth of bytes in memory
as the buffer before flushing the writes to disk, causing a slowness in the logs streamed
back to the client. Every line must be ideally flushed entirely as-its-written, for a smoother
> I suggest changing the line inside {{OperationLog$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:,%20boolean)

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