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From Alan Miller <Alan.Mil...@synopsys.com>
Subject RE: streaming Avro to HDFS
Date Wed, 06 Feb 2013 18:20:30 GMT
Thanks Hari,

Are there any links to examples of how to use the RpcClient?


From: Hari Shreedharan [mailto:hshreedharan@cloudera.com]
Sent: Wednesday, February 06, 2013 7:16 PM
To: user@flume.apache.org
Subject: Re: streaming Avro to HDFS


I think this is probably because the AvroClient is not really very "smart." It is mainly useful
for testing the AvroSource. The AvroClient reads the file passed in, and sends one line per
event (in 1.2.0, in 1.3.0+ there is an option of sending all files in a directory). So the
events are not really sent as Avro files, and since you are using the text serializer they
are dumped as is. Since events can arrive out of order, your data is likely to be invalid
Avro. Also the new line character that is used to split the event may actually have been part
of the real avro serialization, removing it simply made it invalid avro.

My advice would be to use the RpcClient to read the file, and send the data such that you
send the data in a valid format, by making sure one avro "container" is in one event.


Hari Shreedharan

On Wednesday, February 6, 2013 at 9:58 AM, Alan Miller wrote:

Hi I’m just getting started with Flume and trying to understand the flow of things.

I have avro binary data files being generated on remote nodes and I want to use

Flume (1.2.0) to stream them to my HDFS cluster at a central location. It seems I can

stream the data but the resulting files on HDFS seem corrupt.  Here’s what I did:

For my “master” (on the NameNode of my Hadoop cluster)  I started this:

flume-ng agent -f agent.conf  -Dflume.root.logger=DEBUG,console -n agent

With this config:

agent.channels = memory-channel

agent.sources = avro-source

agent.sinks = hdfs-sink

agent.channels.memory-channel.type = memory

agent.channels.memory-channel.capacity = 1000

agent.channels.memory-channel.transactionCapacity = 100

agent.sources.avro-source.channels = memory-channel

agent.sources.avro-source.type = avro

agent.sources.avro-source.bind =

agent.sources.avro-source.port = 41414

agent.sinks.hdfs-sink.type = hdfs

agent.sinks.hdfs-sink.channel = memory-channel

agent.sinks.hdfs-sink.hdfs.path = hdfs://namenode1:9000/flume

On a remote node I streamed a test file like this:

flume-ng avro-client -H -p 41414 -F /tmp/test.avro

I can see the master is writing to HDFS


  13/02/06 09:37:55 INFO hdfs.BucketWriter: Creating hdfs://namenode1:9000/flume/FlumeData.1360172273684.tmp

  13/02/06 09:38:25 INFO hdfs.BucketWriter: Renaming hdfs://namenode1:9000/flume/FlumeData.1360172273684.tmp

  to hdfs://namenode1:9000/flume/FlumeData.1360172273684

But the data doesn’t seem right. The original file is 4551 bytes, the file written to

HDFS was only 219 bytes

  [localhost] $ ls –l FlumeData.1360172273684 /tmp/test.avro

  -rwxr-xr-x 1 amiller amiller  219 Feb  6 18:51 FlumeData.1360172273684

  -rwxr-xr-x 1 amiller amiller 4551 Feb 6 12:00 /tmp/test.avro

  [localhost] $ avro cat /tmp/test.avro

  {"system_model": null, "nfsv4": null, "ip": null, "site": null, "nfsv3": null, "export":
null, "ifnet": [{"send_bps": 1234, "recv_bps": 5678, "name": "eth0"}, {"send_bps": 100, "recv_bps":
200, "name": "eth1"}, {"send_bps": 0, "recv_bps": 0, "name": "eth2"}], "disk": null, "hostname":
"localhost", "total_mem": null, "ontapi_version": null, "serial_number": null, "cifs": null,
"cpu_model": null, "volume": null, "time_stamp": 1357639723, "aggregate": null, "num_cpu":
null, "cpu_speed_mhz": null, "hostid": null, "kernel_version": null, "qtree": null, "processor":

  [localhost] $ hadoop fs -copyToLocal /flume/FlumeData.1360172273684 .

  [localhost] $ avro cat FlumeData.1360172273684

  panic: ord() expected a character, but string of length 0 found


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