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From "Filipe Manana (JIRA)" <>
Subject [jira] Updated: (COUCHDB-639) Make replication profit of attachment compression and improve push replication for large attachments
Date Sat, 20 Feb 2010 11:53:27 GMT


Filipe Manana updated COUCHDB-639:

    Attachment: rep-att-comp-and-multipart-trunk-2.patch

Ok, now I'm no longer using a replication specific URI API. Definitely, it was a bad idea.

For multipart docs, I simply use now a PUT /somedb/docId?new_edits=false.  This is an API
that exists already. Dunno why, but previously I was associating new_edits to _bulk_docs only.

So, for docs without attachments, I upload them to the remote target DB using _bulk_docs,
exactly like before. For docs with attachments, I upload them using PUT /somedb/docId?new_edits=false
and sending the doc as a multipart stream.

Simple enough imho.

> Make replication profit of attachment compression and improve push replication for large
> ----------------------------------------------------------------------------------------------------
>                 Key: COUCHDB-639
>                 URL:
>             Project: CouchDB
>          Issue Type: Improvement
>          Components: Replication
>    Affects Versions: 0.11
>         Environment: trunk
>            Reporter: Filipe Manana
>         Attachments: rep-att-comp-and-multipart-trunk-2.patch, rep-att-comp-and-multipart-trunk.patch
> At the moment, for compressed attachments, the replication uncompresses and then compresses
again the attachments. Therefore, a waste of CPU time.
> The push replication is also not reliable for very large attachments (500mb + for example).
Currently it sends the attachments in-lined in the respective JSON doc. Not only this requires
too much ram memory, it also wastes too much CPU time doing the base64 encoding of the attachment
(and also a decompression if the attachment is compressed).
> The following patch (rep-att-comp-and-multipart-trunk*.patch) addresses both issues.
Docs containing attachments are now streamed to the target remote DB using the multipart doc
streaming feature provided by couch_doc.erl, and compressed attachments are not uncompressed
and re-compressed during the replication
> JavaScript tests included.
> Previously doing a replication of a DB containing 2 docs with attachments of 100mb and
500mb caused the Erlang VM to consume near 1.2GB of ram memory in my system. With that patch
applied, it uses about 130Mb of ram memory.

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