[jira] [Comment Edited] (AVRO-1704) Standardized format for encoding messages with Avro

["Niels Basjes (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/AVRO-1704?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15234304#comment-15234304 ] 

Niels Basjes edited comment on AVRO-1704 at 4/10/16 10:10 PM:
--------------------------------------------------------------

During the last few weeks I spent some time figuring out what I think the format should be. I created this patch which includes specification for the new format, code generators for Java and unit tests that validate the format in light of schema evolution and corrupt data.

I documented the new format as follows:
{quote}
Schema tagged Binary Encoding specification

The wrapper format consists of a header and a body.
The header is always the 4 bytes representing the UTF-8 of the word "Avro" followed by a single byte indicating the version of the body format.

Version 0 of the body (currently the ONLY body format that has been defined) consists of:
#  the finger print (see the section about Schema Fingerprints of the schema (a 64 bit long) that was written in the same byte order as a long is when written if it was a field in a record.
# the record serialized to byte using the binary encoding.
{quote}

Although I think this is already "pretty good" I really think this needs your comments and improvement suggestions.

Thanks.


was (Author: nielsbasjes):
During the last few weeks I spent some time figuring out what I think the format should be. I created this patch which includes specification for the new format, code generators for Java and unit tests that validate the format in light of schema evolution and corrupt data.

I documented the new format as follows:
{quote}
Schema tagged Binary Encoding specification

The wrapper format consists of a header and a body.
The header is always the 4 bytes representing the UTF-8 of the word "Avro" followed by a single byte indicating the version of the body format.

Version 0 of the body (currently the ONLY body format that has been defined) consists of:
#  the finger print (see the section about Schema Fingerprints of the schema (a 64 bit long) that was written in the same byte order as a long is when written if it was a field in a record.
# the record serialized to byte using the binary encoding.
{quote}

Although I thing this is already "pretty good" I really think this needs your comments and improvement suggestions.

Thanks.

> Standardized format for encoding messages with Avro
> ---------------------------------------------------
>
>                 Key: AVRO-1704
>                 URL: https://issues.apache.org/jira/browse/AVRO-1704
>             Project: Avro
>          Issue Type: Improvement
>            Reporter: Daniel Schierbeck
>            Assignee: Niels Basjes
>         Attachments: AVRO-1704-20160410.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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