FAQ
Hi Jagaran,

Short answer: the append feature is not in any release. In this sense, it is
not stable. Below are more details on the Append feature status.

- 0.20.x (includes release 0.20.2)
There are known bugs in append. The bugs may cause data loss.

- 0.20-append
There were effort on fixing the known append bugs but there are no releases. I
heard Facebook was using it (with additional patches?) in production but I did
not have the details.

- 0.21
It has a new append design (HDFS-265). However, the 0.21.0 release is only a
minor release. It has not undergone testing at scale and should not be
considered stable or suitable for production. Also, 0.21 development has been
discontinued. Newly discovered bugs may not be fixed.

- 0.22, 0.23
Not yet released.


Regards,
Tsz-Wo




________________________________
From: jagaran das <jagaran_das@yahoo.co.in>
To: common-user@hadoop.apache.org
Sent: Fri, June 17, 2011 11:15:04 AM
Subject: Fw: HDFS File Appending URGENT

Please help me on this.
I need it very urgently

Regards,
Jagaran


----- Forwarded Message ----
From: jagaran das <jagaran_das@yahoo.co.in>
To: common-user@hadoop.apache.org
Sent: Thu, 16 June, 2011 9:51:51 PM
Subject: Re: HDFS File Appending URGENT

Thanks a lot Xiabo.

I have tried with the below code in HDFS version 0.20.20 and it worked.
Is it not stable yet?

public class HadoopFileWriter {
public static void main (String [] args) throws Exception{
try{
URI uri = new
URI("hdfs://localhost:9000/Users/jagarandas/Work-Assignment/Analytics/analytics-poc/hadoop-0.20.203.0/data/test.dat");



Path pt=new Path(uri);
FileSystem fs = FileSystem.get(new Configuration());
BufferedWriter br;
if(fs.isFile(pt)){
br=new BufferedWriter(new OutputStreamWriter(fs.append(pt)));
br.newLine();
}else{
br=new BufferedWriter(new OutputStreamWriter(fs.create(pt,true)));
}
String line = args[0];
System.out.println(line);
br.write(line);
br.close();
}catch(Exception e){
e.printStackTrace();
System.out.println("File not found");
}
}
}

Thanks a lot for your help.

Regards,
Jagaran




________________________________
From: Xiaobo Gu <guxiaobo1982@gmail.com>
To: common-user@hadoop.apache.org
Sent: Thu, 16 June, 2011 8:01:14 PM
Subject: Re: HDFS File Appending URGENT

You can merge multiple files into a new one, there is no means to
append to a existing file.
On Fri, Jun 17, 2011 at 10:29 AM, jagaran das wrote:
Is the hadoop version Hadoop 0.20.203.0 API

That means still the hadoop files in HDFS version 0.20.20 are immutable?
And there is no means we can append to an existing file in HDFS?

We need to do this urgently as we have do set up the pipeline accordingly in
production?

Regards,
Jagaran



________________________________
From: Xiaobo Gu <guxiaobo1982@gmail.com>
To: common-user@hadoop.apache.org
Sent: Thu, 16 June, 2011 6:26:45 PM
Subject: Re: HDFS File Appending

please refer to FileUtil.CopyMerge
On Fri, Jun 17, 2011 at 8:33 AM, jagaran das wrote:
Hi,

We have a requirement where

There would be huge number of small files to be pushed to hdfs and then use
pig
to do analysis.
To get around the classic "Small File Issue" we merge the files and push a
bigger file in to HDFS.
But we are loosing time in this merging process of our pipeline.

But If we can directly append to an existing file in HDFS we can save this
"Merging Files" time.

Can you please suggest if there a newer stable version of Hadoop where can go
for appending ?

Thanks and Regards,
Jagaran

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