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Posted to oak-issues@jackrabbit.apache.org by "Michael Dürig (JIRA)" <ji...@apache.org> on 2015/02/16 16:44:11 UTC
[jira] [Updated] (OAK-2527) Update SegmentMK header format
[ https://issues.apache.org/jira/browse/OAK-2527?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Michael Dürig updated OAK-2527:
-------------------------------
Fix Version/s: 1.1.8
1.0.12
> Update SegmentMK header format
> ------------------------------
>
> Key: OAK-2527
> URL: https://issues.apache.org/jira/browse/OAK-2527
> Project: Jackrabbit Oak
> Issue Type: Improvement
> Components: segmentmk
> Reporter: Michael Dürig
> Assignee: Michael Dürig
> Fix For: 1.0.12, 1.1.8
>
>
> Even though the Oak's [segment header format | http://jackrabbit.apache.org/oak/docs/nodestore/segmentmk.html] defines a version, that version is not checked when running Oak. In effect this means current Oak versions pretend to be infinitely forward compatible.
> To prevent older versions of Oak to run with incompatible, newer storage formats we need to devise a way for Oak to fail fast in that scenario.
> One thing we could do to introduce versions checking retroactively is to redefine the segment header format from:
> {noformat}
> +--------+--------+--------+--------+--------+--------+--------+--------+
> | magic bytes: "0aK\n" in ASCII |version |idcount |rootcount |
> +--------+--------+--------+--------+--------+--------+--------+--------+
> {noformat}
> to:
> {noformat}
> +--------+--------+--------+--------+--------+--------+--------+--------+
> | magic bytes: "0aK" ASCII |version |reserved|idcount |rootcount |
> +--------+--------+--------+--------+--------+--------+--------+--------+
> {noformat}
> where version would be {{10}} for the current storage format and {{11}} for the next storage format.
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