Thank you Verardi!

Sorry for my poor English that making my question ambiguously. =A0You= r answer is so clearly.=A0=A0Now I know that the byte arrays can be = used as "values" for the field "tuple".

One more question, In my project, = I emit byte array tuples in KafakSpout like this:

=A0 =A0 List<Object> tup =3D _spoutConfig.= scheme.deserialize(Utils.toByteArray(toEmit.msg.payload())); =A0// byte arr= ay

=A0 =A0 collector.emit= (tup), new KafkaMessageId(_partition, toEmit.offset));

But when I tried to get tuple in ShellB= olt, readMsgs() got an exception. And I write the emitting JSON message to = file, it looks like:

{"id":"7617035644= 022584549","stream":"default","comp":&qu= ot;KafkaSpout","tuple":[[B@6d695bcc],"task":1}=

It looks very weird fo= r me. What is the=A0[[B@= 6d695bcc]? Is it a byte = array's object address? Can It be read by Python?

Going even further, If = I insist on emitting byte arrays in KafkaSpout, What should I do to readMsg= s in Python Bolt?=A0

2014/1/9 Antonio Verardi <antonio@yelp.com>

Hi,
=
I am extensively using the multilang interface for Python. JSON i= s the way you serialize things for communication. It adds a fairly amount o= f overhead, but it is a reasonable design choice in terms of a multilang in= terface.

If your question is: can I read byte array messages from a bolt (made u= p by command, id, stream, task and tuple), the answer is "that's n= ot that easy, you should implement something in order to do that".

If your question is: can I serialize byte arrays in JSON with Pyt= hon and use them as "values" for the field "tuple", the= answer is: "yes, even though JSON always produce string objects"= . [http://docs.python.org/3.3/library/json.html#basic-usage= ]. You may want to modify storm.py, in order to do that, or simply encode a= nd decode your data within your own bolt, it depends on your needs.

This is something I found just googling about encoding binary data in J= SON:
http://bytes.com/topic/python/answers/6= 81314-simplejson-pack-binary-data

I hope it was what you were looking for,
Antonio Uccio V= erardi
On= Tue, Jan 7, 2014 at 11:24 PM, churly lin <churylin@gmail.com> wrote:

Hi all,
<= br>

I am trying to write a topolo= gy with a KafkaSpout and a ShellBolt(implemented by python ).

According to the=A0Multilang-protocol, multilang=A0uses json messages over stdin/stdout to communicate with= the subprocess. Specially, both ends of this protocol use a line-readin= g mechanism. Does it mean that, in multilang, we could not emit message= as byte array? If not, how to read a byte array tuple in a python bolt ?

the json which was read by python bolt is look like= :
{ "command": = "emit", // The id = for the tuple. Leave this out for an unreliable emit. The id can // be a string= or a number. "id": "= ;1231231", // The id = of the stream this tuple was emitted to. Leave this empty to emit to defaul= t stream. "stream": &= quot;1", // If doin= g an emit direct, indicate the task to send the tuple to "task": 9, // All the= values in this tuple "tuple": [&= quot;field1", 2, 3]}
This example shows that, the &quo= t;tuple" can be String("field1") and number(2, 3). Could it = be a byte array?