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From "radai rosenblatt (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (AVRO-1704) Standardized format for encoding messages with Avro
Date Thu, 13 Oct 2016 16:40:20 GMT

    [ https://issues.apache.org/jira/browse/AVRO-1704?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15572449#comment-15572449
] 

radai rosenblatt commented on AVRO-1704:
----------------------------------------

Also, since this is somewhat Kafka related, i would like to point to this kafka proposal for
headers in the kafka wire format - https://cwiki.apache.org/confluence/display/KAFKA/KIP-82+-+Add+Record+Headers
discussion thread is here - http://mail-archives.apache.org/mod_mbox/kafka-dev/201609.mbox/%3C1474572662302.81658%40ig.com%3E

> Standardized format for encoding messages with Avro
> ---------------------------------------------------
>
>                 Key: AVRO-1704
>                 URL: https://issues.apache.org/jira/browse/AVRO-1704
>             Project: Avro
>          Issue Type: Improvement
>          Components: java, spec
>            Reporter: Daniel Schierbeck
>            Assignee: Niels Basjes
>             Fix For: 1.9.0, 1.8.3
>
>         Attachments: AVRO-1704-2016-05-03-Unfinished.patch, AVRO-1704-20160410.patch,
AVRO-1704.3.patch, AVRO-1704.4.patch
>
>
> I'm currently using the Datafile format for encoding messages that are written to Kafka
and Cassandra. This seems rather wasteful:
> 1. I only encode a single record at a time, so there's no need for sync markers and other
metadata related to multi-record files.
> 2. The entire schema is inlined every time.
> However, the Datafile format is the only one that has been standardized, meaning that
I can read and write data with minimal effort across the various languages in use in my organization.
If there was a standardized format for encoding single values that was optimized for out-of-band
schema transfer, I would much rather use that.
> I think the necessary pieces of the format would be:
> 1. A format version number.
> 2. A schema fingerprint type identifier, i.e. Rabin, MD5, SHA256, etc.
> 3. The actual schema fingerprint (according to the type.)
> 4. Optional metadata map.
> 5. The encoded datum.
> The language libraries would implement a MessageWriter that would encode datums in this
format, as well as a MessageReader that, given a SchemaStore, would be able to decode datums.
The reader would decode the fingerprint and ask its SchemaStore to return the corresponding
writer's schema.
> The idea is that SchemaStore would be an abstract interface that allowed library users
to inject custom backends. A simple, file system based one could be provided out of the box.



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