i'm really just trying to emit "results" into an hdfs file at
different moments of the computation. I'm really just thinking at a
functionality like log.debug(), to give an example, where all the
messages are collected from different workers at different supersteps.
At the moment I've implemented this:

https://github.com/claudiomartella/graffiti/blob/master/src/main/java/org/acaro/graffiti/processing/GraffitiEmitter.java

which i assign to each vertex at preApplication() and close from each
vertex at postApplication(). I'm not super happy about this solution.
During this weekend though, I thought I might use an Aggregator to
send my ResultSet object and use the Aggregator to write to disk. That
would be a nice design and I could contribute the JIRA about storing
Aggregator results.

What do you think?

On Fri, Sep 23, 2011 at 1:40 AM, Avery Ching <avery.ch...@gmail.com> wrote:
> This is more of a limitation of the fact that files are immutable in HDFS.
>  Any more insight on what you're trying to do?  Perhaps we can think of a
> more general way to address the issue.
>
> Avery
>
> On 9/22/11 10:31 AM, Claudio Martella wrote:
>>
>> Hi Avery,
>>
>> thanks, yes it does. The question would be though how to share the
>> file handle between the vertices on the same node. i could open the
>> file on the preApplication() and close it on the postApplication() but
>> i would end up potentially with as many files as vertices in the
>> graph.
>>
>> Do you have any idea on this side? Maybe share somehow the handle and a
>> lock?
>>
>> On Thu, Sep 22, 2011 at 4:07 PM, Avery Ching<ach...@apache.org>  wrote:
>>>
>>> There are some methods in Vertex (i.e. preApplication(), preSuperstep(),
>>> postApplication(), postSuperstep()) that can be overidden to do anything
>>> you
>>> like, for instance write out some data to an HDFS file.  We have an open
>>> issue on outputting Aggregator values that is unassigned if you'd like to
>>> take a look at it as well
>>> (https://issues.apache.org/jira/browse/GIRAPH-10).
>>>
>>> Hope this helps,
>>>
>>> Avery
>>>
>>> On 9/22/11 7:34 AM, Claudio Martella wrote:
>>>>
>>>> Hello list,
>>>>
>>>> I have the need to emit to HDFS once in a while some Text. This
>>>> doesn't happen necessarily at the end of the computation and I might
>>>> need to emit something more complex than just the VertexValue, so I'd
>>>> like more control than what the VertexWriter gives me.
>>>>
>>>> What do you suggest I might do to obtain a handler to a HDFS file (it
>>>> can be in parts aswell) to write to?
>>>> Is there any code I can start looking at?
>>>>
>>>> Thanks!
>>>> Claudio
>>>>
>>>
>>
>>
>
>



-- 
    Claudio Martella
    claudio.marte...@gmail.com

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