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https://issues.apache.org/jira/browse/NIFI-2854?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15677581#comment-15677581
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ASF subversion and git services commented on NIFI-2854:
-------------------------------------------------------
Commit 1be08714731f01347ac1f98e18047fe7d9ab8afd in nifi's branch
refs/heads/master from [~markap14]
[ https://git-wip-us.apache.org/repos/asf?p=nifi.git;h=1be0871 ]
NIFI-2854: Refactor repositories and swap files to use schema-based
serialization so that nifi can be rolled back to a previous version after an
upgrade.
NIFI-2854: Incorporated PR review feedback
NIFI-2854: Implemented feedback from PR Review
NIFI-2854: Ensure that all resources are closed on
CompressableRecordReader.close() even if an IOException is thrown when closing
one of them
This closes #1202
> Enable repositories to support upgrades and rollback in well defined scenarios
> ------------------------------------------------------------------------------
>
> Key: NIFI-2854
> URL: https://issues.apache.org/jira/browse/NIFI-2854
> Project: Apache NiFi
> Issue Type: Improvement
> Components: Core Framework
> Reporter: Mark Payne
> Assignee: Mark Payne
> Fix For: 1.1.0
>
>
> The flowfile, swapfile, provenance, and content repositories play a very
> important roll in NiFi's ability to be safely upgraded and rolled back. We
> need to have well documented behaviors, designs, and version adherence so
> that users can safely rely on these mechanisms.
> Once this is formalized and in place we should update our versioning guidance
> to reflect this as well.
> The following would be true from NiFi 1.2.0 onward
> * No changes to how the repositories are persisted to disk can be made which
> will break forward/backward compatibility and specifically this means that
> things like the way each is serialized to disk cannot change.
> * If changes are made which impact forward or backward compatibility they
> should be reserved for major releases only and should include a utility to
> help users with pre-existing data convert from some older format to the newer
> format. It may not be feasible to have rollback on major releases.
> * The content repository should not be changed within a major release cycle
> in any way that will harm forward or backward compatibility.
> * The flow file repository can change in that new fields can be added to
> existing write ahead log record types but no fields can be removed nor can
> any new types be added. Once a field is considered required it must remain
> required. Changes may only be made across minor version changes - not
> incremental.
> * Swap File storage should follow very similar rules to the flow file
> repository. Adding a schema to the swap file header may allow some variation
> there but the variation should only be hints to optimize how they're
> processed and not change their behavior otherwise. Changes are only permitted
> during minor version releases.
> * Provenance repository changes are only permitted during minor version
> releases. These changes may include adding or removing fields from existing
> event types. If a field is considered required it must always be considered
> required. If a field is removed then it must not be a required field and
> there must be a sensible default an older version could use if that value is
> not found in new data once rolled back. New event types may be added.
> Fields or event types not known to older version, if seen after a rollback,
> will simply be ignored.
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