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From Fabio <anyte...@gmail.com>
Subject Re: Timestamp reliability (log4j in Hadoop)
Date Mon, 26 Jan 2015 12:54:22 GMT
Thanks Gary, indeed I forced a timestamp into the string passed to the 
log and, comparing it with the log timestamp itself, the difference is 
within 1 ms.

Regards

Fabio

On 01/26/2015 01:44 PM, Gary Gregory wrote:
> On Mon, Jan 26, 2015 at 3:44 AM, Fabio <anytek88@gmail.com> wrote:
>
>> Hi everyone,
>> I am using Hadoop, that uses log4j as logging system.
>> Since I don't know anything about how log4j works, and since I am relying
>> on the logs for my work, I would like to ask you how reliable is the
>> timestamp I see in the logs.
>> Is each timestamp I see the exact real system time at which each
>> "LOG.info(...)" function is called within the Hadoop code?
>
> Yes. The info() call creates a log event object which includes a timestamp.
> Exactly when the log event is used and how is up to each appender
> implementation.
>
> Gary
>
>
>> Or is the log request enqueued in some buffer so that the timestamp
>> includes some delay to process the entries in this buffer?
>> I asked this in the Hadoop mailing list but with no answer, hope to have
>> more luck here.
>>
>> Thanks in advance
>>
>> Fabio
>>
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>


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