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From Stuti Awasthi <stutiawas...@hcl.com>
Subject RE: Issue in access static object in MapReduce
Date Wed, 12 Sep 2012 04:30:29 GMT
Thanks Bejoy,
I try to implement and if face any issues will let you know.

Thanks
Stuti

From: Bejoy Ks [mailto:bejoy.hadoop@gmail.com]
Sent: Tuesday, September 11, 2012 8:39 PM
To: user@hadoop.apache.org
Subject: Re: Issue in access static object in MapReduce

Hi Stuti

You can pass the json object as a configuration property from your main class then Initialize
this static json object on the configure() method. Every instance of map or reduce task will
have this configure() method executed once before the map()/reduce() function . So all the
executions of map()/reduce() on each record can have a look up into the json object.

public void configure(JobConf job)

Regards
Bejoy KS
On Tue, Sep 11, 2012 at 8:23 PM, Stuti Awasthi <stutiawasthi@hcl.com<mailto:stutiawasthi@hcl.com>>
wrote:


Hi,

I have a configuration JSON file which is accessed by MR job for every input.So , I created
a class with a static block, load the JSON file in static Instance variable.

So everytime my mapper or reducer wants to access configuration can use this Instance variable.
But on a single node cluster,when I run this as a jar, my mapper is executing fine,

But in reducer static Instance variable is retuning "null".



I get this mainly because mapper and reducer runs on separate jvms. How can I handle this
situation gracefully. There are few ways that I can think of:



1.  Serialize the JSON load object and store it on HDFS and then deserialize and use in the
code. Problem is obj is not too large so not be useful to store on HDFS

2. I load the JSON for every Input line of map reduce call. This is highly inefficient and
 as Il be loading JSON for so many lines again and again.



How to resolve this issue.. Any Inputs  are welcome.



Note , same code works with eclipse well. :(



Thanks

Stuti



Regards,
Stuti Awasthi
HCL Comnet Systems and Services Ltd



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