Hi,

  I wrote a simple map reduce job in hadoop streaming.

I am wondering if I am doing something wrong ..

While number of mappers are projected to be around 1700.. reducers.. just 1?

It’s couple of TB’s worth of data.

What can I do to address this.

Basically mapper looks like this

For line in sys.stdin:

    Print line

Reducer

For line in sys.stdin:

    New_line = process_line(line)

    Print new_line

Thanks

Hi Sasha

By default the number or reducers are set to be 1. If you want more you need to specify it as

hadoop jar myJar.jar myClass -D mapred.reduce.tasks=20 ...
Regards
Bejoy KS

Sent from handheld, please excuse typos.

-----Original Message-----
From: jamal sasha <[EMAIL PROTECTED]>
Date: Tue, 20 Nov 2012 14:38:54
To: <[EMAIL PROTECTED]>
Reply-To: [EMAIL PROTECTED]
Subject: number of reducers

Hi,

  I wrote a simple map reduce job in hadoop streaming.

I am wondering if I am doing something wrong ..

While number of mappers are projected to be around 1700.. reducers.. just 1?

It’s couple of TB’s worth of data.

What can I do to address this.

Basically mapper looks like this

For line in sys.stdin:

    Print line

Reducer

For line in sys.stdin:

    New_line = process_line(line)

    Print new_line

Thanks

I specify mine inside mapred-site.xml

<property>
    <name>mapred.reduce.tasks</name>
    <value>20</value>
  </property>

Rgds,
AK47
From: Bejoy KS [mailto:[EMAIL PROTECTED]]
Sent: Tuesday, November 20, 2012 3:10 PM
To: [EMAIL PROTECTED]
Subject: Re: number of reducers

Hi Sasha

By default the number or reducers are set to be 1. If you want more you need to specify it as

hadoop jar myJar.jar myClass -D mapred.reduce.tasks=20 ...
Regards
Bejoy KS

Sent from handheld, please excuse typos.
________________________________
From: jamal sasha <[EMAIL PROTECTED]>
Date: Tue, 20 Nov 2012 14:38:54 -0500
To: <[EMAIL PROTECTED]>
ReplyTo: [EMAIL PROTECTED]
Subject: number of reducers

Hi,

  I wrote a simple map reduce job in hadoop streaming.

I am wondering if I am doing something wrong ..

While number of mappers are projected to be around 1700.. reducers.. just 1?

It's couple of TB's worth of data.

What can I do to address this.

Basically mapper looks like this

For line in sys.stdin:

    Print line

Reducer

For line in sys.stdin:

    New_line = process_line(line)

    Print new_line

Thanks

NOTICE: This e-mail message and any attachments are confidential, subject to copyright and may be privileged. Any unauthorized use, copying or disclosure is prohibited. If you are not the intended recipient, please delete and contact the sender immediately. Please consider the environment before printing this e-mail. AVIS : le pr?sent courriel et toute pi?ce jointe qui l'accompagne sont confidentiels, prot?g?s par le droit d'auteur et peuvent ?tre couverts par le secret professionnel. Toute utilisation, copie ou divulgation non autoris?e est interdite. Si vous n'?tes pas le destinataire pr?vu de ce courriel, supprimez-le et contactez imm?diatement l'exp?diteur. Veuillez penser ? l'environnement avant d'imprimer le pr?sent courriel

 What is the relationship between number of reducers and cpu cores in your setup? I read somewhere that it must be .5 of number of cpu cores.

Thanks.
Alex.

 

 

-----Original Message-----
From: Kartashov, Andy <[EMAIL PROTECTED]>
To: user <[EMAIL PROTECTED]>; bejoy.hadoop <[EMAIL PROTECTED]>
Sent: Tue, Nov 20, 2012 1:51 pm
Subject: RE: number of reducers

I specify mine inside mapred-site.xml
 
<property>
    <name>mapred.reduce.tasks</name>
    <value>20</value>
  </property>
 
Rgds,
AK47

From: Bejoy KS [mailto:[EMAIL PROTECTED]]
Sent: Tuesday, November 20, 2012 3:10 PM
To: [EMAIL PROTECTED]
Subject: Re: number of reducers

 
Hi Sasha

By default the number or reducers are set to be 1. If you want more you need to specify it as

hadoop jar myJar.jar myClass -D mapred.reduce.tasks=20 ...

Regards
Bejoy KS

Sent from handheld, please excuse typos.

From: jamal sasha <[EMAIL PROTECTED]>

Date: Tue, 20 Nov 2012 14:38:54 -0500

To: <[EMAIL PROTECTED]>

ReplyTo: [EMAIL PROTECTED]

Subject: number of reducers

 

Hi,

  I wrote a simple map reduce job in hadoop streaming.

 

I am wondering if I am doing something wrong ..

While number of mappers are projected to be around 1700.. reducers.. just 1?

It’s couple of TB’s worth of data.

What can I do to address this.

Basically mapper looks like this

 

For line in sys.stdin:

    Print line

 

Reducer

For line in sys.stdin:

    New_line = process_line(line)

    Print new_line

 

 

Thanks
NOTICE: This e-mail message and any attachments are confidential, subject to copyright and may be privileged. Any unauthorized use, copying or disclosure is prohibited. If you are not the intended recipient, please delete and contact the sender immediately. Please consider the environment before printing this e-mail. AVIS : le présent courriel et toute pièce jointe qui l'accompagne sont confidentiels, protégés par le droit d'auteur et peuvent être couverts par le secret professionnel. Toute utilisation, copie ou divulgation non autorisée est interdite. Si vous n'êtes pas le destinataire prévu de ce courriel, supprimez-le et contactez immédiatement l'expéditeur. Veuillez penser à l'environnement avant d'imprimer le présent courriel
 

Awesome thanks . Works great now

On Tuesday, November 20, 2012, Bejoy KS <[EMAIL PROTECTED]> wrote:
> Hi Sasha
>
> By default the number or reducers are set to be 1. If you want more you
need to specify it as
>
> hadoop jar myJar.jar myClass -D mapred.reduce.tasks=20 ...
>
> Regards
> Bejoy KS
>
> Sent from handheld, please excuse typos.
> ________________________________
> From: jamal sasha <[EMAIL PROTECTED]>
> Date: Tue, 20 Nov 2012 14:38:54 -0500
> To: <[EMAIL PROTECTED]>
> ReplyTo: [EMAIL PROTECTED]
> Subject: number of reducers
>
>
> Hi,
>
>   I wrote a simple map reduce job in hadoop streaming.
>
>
>
> I am wondering if I am doing something wrong ..
>
> While number of mappers are projected to be around 1700.. reducers.. just
1?
>
> It’s couple of TB’s worth of data.
>
> What can I do to address this.
>
> Basically mapper looks like this
>
>
>
> For line in sys.stdin:
>
>     Print line
>
>
>
> Reducer
>
> For line in sys.stdin:
>
>     New_line = process_line(line)
>
>     Print new_line
>
>
>
>
>
> Thanks
>
>
>

Hey Jamal,

I'd recommend first going over the whole tutorial to get a good grip
on how Hadoop MR is designed to work:
http://hadoop.apache.org/docs/stable/mapred_tutorial.html

On Wed, Nov 21, 2012 at 1:08 AM, jamal sasha <[EMAIL PROTECTED]> wrote:
>
>
> Hi,
>
>   I wrote a simple map reduce job in hadoop streaming.
>
>
>
> I am wondering if I am doing something wrong ..
>
> While number of mappers are projected to be around 1700.. reducers.. just 1?
>
> It’s couple of TB’s worth of data.
>
> What can I do to address this.
>
> Basically mapper looks like this
>
>
>
> For line in sys.stdin:
>
>     Print line
>
>
>
> Reducer
>
> For line in sys.stdin:
>
>     New_line = process_line(line)
>
>     Print new_line
>
>
>
>
>
> Thanks
>
>

--
Harsh J