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MapReduce >> mail # user >> Why LineRecordWriter.write(..) is synchronized


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Re: Why LineRecordWriter.write(..) is synchronized
Then is this a bug?  Synchronization in absence of any race condition is normally considered "bad".

In any case id like to know why this writer is synchronized whereas the other one are not.. That is, I think, then point at issue: either other writers should be synchronized or else this one shouldn't be - consistency across the write implementations is probably desirable so that changes to output formats or record writers don't lead to bugs in multithreaded environments .

On Aug 8, 2013, at 6:50 AM, Harsh J <[EMAIL PROTECTED]> wrote:

> While we don't fork by default, we do provide a MultithreadedMapper implementation that would require such synchronization. But if you are asking is it necessary, then perhaps the answer is no.
>
> On Aug 8, 2013 3:43 PM, "Azuryy Yu" <[EMAIL PROTECTED]> wrote:
>> its not hadoop forked threads, we may create a line record writer, then call this writer concurrently.
>>
>> On Aug 8, 2013 4:00 PM, "Sathwik B P" <[EMAIL PROTECTED]> wrote:
>>> Hi,
>>> Thanks for your reply.
>>> May I know where does hadoop fork multiple threads to use a single RecordWriter.
>>>
>>> regards,
>>> sathwik
>>>
>>> On Thu, Aug 8, 2013 at 7:06 AM, Azuryy Yu <[EMAIL PROTECTED]> wrote:
>>>> because we may use multi-threads to write a single file.
>>>>
>>>> On Aug 8, 2013 2:54 PM, "Sathwik B P" <[EMAIL PROTECTED]> wrote:
>>>>> Hi,
>>>>>
>>>>> LineRecordWriter.write(..) is synchronized. I did not find any other RecordWriter implementations define the write as synchronized.
>>>>> Any specific reason for this.
>>>>>
>>>>> regards,
>>>>> sathwik