Potential Issues
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Switching between unencrypted and encrypted repositories
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If a user has an existing repository (
WriteAheadProvenanceRepositoryonly - notPersistentProvenanceRepository) that is not encrypted and switches their configuration to use an encrypted repository, the application writes an error to the log but starts up. However, previous events are not accessible through the provenance query interface and new events will overwrite the existing events. The same behavior occurs if a user switches from an encrypted repository to an unencrypted repository. Automatic roll-over is a future effort (https://issues.apache.org/jira/browse/NIFI-3722) but NiFi is not intended for long-term storage of provenance events so the impact should be minimal. There are two scenarios for roll-over:-
Encrypted → unencrypted - if the previous repository implementation was encrypted, these events should be handled seamlessly as long as the key provider available still has the keys used to encrypt the events (see Provenance Repository Key Rotation)
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Unencrypted → encrypted - if the previous repository implementation was unencrypted, these events should be handled seamlessly as the previously recorded events simply need to be read with a plaintext schema record reader and then written back with the encrypted record writer
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There is also a future effort to provide a standalone tool in NiFi Toolkit to encrypt/decrypt an existing provenance repository to make the transition easier. The translation process could take a long time depending on the size of the existing repository, and being able to perform this task outside of application startup would be valuable (https://issues.apache.org/jira/browse/NIFI-3723).
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Multiple repositories - No additional effort or testing has been applied to multiple repositories at this time. It is possible/likely issues will occur with repositories on different physical devices. There is no option to provide a heterogenous environment (i.e. one encrypted, one plaintext repository).
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Corruption - when a disk is filled or corrupted, there have been reported issues with the repository becoming corrupted and recovery steps are necessary. This is likely to continue to be an issue with the encrypted repository, although still limited in scope to individual records (i.e. an entire repository file won't be irrecoverable due to the encryption).