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Date: Tue, 7 Jul 2009 20:20:43 +0800 (CST)
From: Andy <lamfeeling@126.com>
To: common-user <common-user@hadoop.apache.org>,
	"shravan.mahankali" <shravan.mahankali@catalytic.com>
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Subject: Re:how to use hadoop in real life?
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Hi, befor you resubmit your program, please make sure your output path is "=
valid". The valid condition depends on your outputformat. In the case of Fi=
leOutputFomrat, this means, your output dir should not exist. So try to del=
ete them first.
=20
you have various methods to initiate your hadoop program. try to refer to s=
ome "classic" hadoop programs, such as Nutch, a totally hadoop based search=
 engine. Find how many ways that you can deploy and run a hadoop program.

to my knowledge, you can submit your hadoop program anywhere, as long as yo=
u can access the "master" machine through network.
=20
what kind of report?
not a good idea to replace your database with hadoop storage. the design of=
 hadoop aims the high I/O utility when dealing a large scale of data. So, m=
aybe it is not appropriate to treat hadoop as distributed database. BTW, th=
e hbase project may be useful for you.
this is simple, use the HDFS APIs, you can do any file operation on HDFS re=
motely.
Java is a powerful language for most hadoop programmer, again, try to get f=
amiliar with some Java written hadoop projects, you will find it is convien=
ent to do your things.
Best wishes
Song
=D4=DA2009-07-06?20:25:49=A3=AC"Shravan?Mahankali"?<shravan.mahankali@catal=
ytic.com>?=D0=B4=B5=C0=A3=BA
>Hi?Group,
>
>?
>
>Finally?I?have?written?a?sample?Mapred?program,?submitted?this?job?to?Hado=
op
>and?got?the?expected?results.?Thanks?to?all?of?you!
>
>?
>
>Now?I?don't?have?an?idea?of?how?to?use?Hadoop?in?real?life?(am?sorry?if?am
>asking?wrong?question?at?wrong?time.!?(So,?am?right?;-)))?:
>
>?
>
>1)?If?I?re-submit?my?job,?Hadoop?responds?with?an?error?message?saying:
>org.apache.hadoop.mapred.FileAlreadyExistsException:?Output?directory
>hdfs://localhost:9000/user/root/impressions_output?already?exists
>
>2)?How?to?automatically?execute?Hadoop?jobs??let's?say?I?have?set?a?cron?j=
ob
>which?runs?various?Hadoop?jobs?at?specified?times.?Is?this?the?way?we?do?i=
n
>Hadoop?world?
>
>3)?Can?I?submit?jobs?to?Hadoop?from?a?different?machine/?network/?domain?
>
>4)?I?would?like?to?generate?reports?from?the?data?collected?in?the?Hadoop.
>How?can?I?do?that?
>
>5)?Am?thinking?of?replacing?data?in?my?database?with?Hadoop?and?query?Hado=
op
>for?various?information.?Is?this?correct?
>
>6)?How?can?I?access?analyzed?data?in?Hadoop?from?external?world,?external
>program?
>
>?
>
>NOTE:?I?would?like?to?use?Java?for?any?of?above?implementations.
>
>?
>
>Thanks?in?advance,
>
>Shravan?Kumar.?M?
>
>Catalytic?Software?Ltd.?[SEI-CMMI?Level?5?Company]
>
>-----------------------------
>
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>?
>

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