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From Wai Yip Tung ...@tungwaiyip.info>
Subject Re: Schema exclusion from Avro message
Date Tue, 28 Jan 2014 01:09:24 GMT
I'm planning to stream it via Kafka.

I think I've sorted it out. The Object Container Files is not an 
essential part of the Avro. Instead of using 
DataFileReader/DataFileWriter, I can use DatumReader/DatumWriter to 
encode and decode the binary data and store the schema separately.

Wai Yip



> Doug Cutting <mailto:cutting@apache.org>
> Monday, January 27, 2014 11:50 AM
> If you're using Avro's RPC mechanism, schemas are only sent when the
> client and server do not already have each other's schema. Each
> client request is preceded by a hash of the clients schema and the
> schema it thinks the server is using. If the server already has the
> client's schema, and the client already has the server's, then the
> server can directly respond. If they do not have the other's schema
> then schemas are transmitted and cached. This way the server's schema
> is only transmitted for the first request from a given client, and the
> client's schema is only transmitted to the server the first time a
> client with that schema connects.
>
> Avro Python does support RPC.
>
> If you're not using Avro RPC but some other messaging mechanism, then
> AVRO-1124 as you mention might be useful, but it also has not yet been
> released.
>
> If you're storing Avro data in a file, then the Schema is included in
> the file, as you mention.
>
> Doug
>
> Wai Yip Tung <mailto:wy@tungwaiyip.info>
> Monday, January 27, 2014 11:00 AM
> I found Deepesh's question back in December. I have joined the mailing 
> list later. So don't have the message in my inbox and I do not know 
> the proper way to reply. Anyway I have include the original message 
> below.
>
> I have the similar issue. In addition I'm interested to find out about 
> Python and Node js library support.
>
> From what I understand, the avro specification requires avro.schema. 
> So I am quite unsure of the status of have the schema in an external 
> repository.
>
> -  avro.schema contains the schema of objects stored in the file, as 
> JSON data (required).
>
> http://avro.apache.org/docs/1.7.6/spec.html#Object+Container+Files
>
> Wai Yip
>
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