Improve DataConflictException handling in case of partial local modification #409
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added 2 commits
June 28, 2016 11:25
…t, the maxPatchSyncCount will not reset the dataset sync count sufficiently.
… by the same device during sync. When a record is updated during the sync operation, it's meta data will not be updated, even though the prior local modification was written to the server, and the sync count was updated. During the next sync operation, the put to remote will fail, due to a data conflict exception (modifying a stale sync count). The data conflict exception handling will then fall back to an older sync count for the dataset and try again. This will lead to a case where the local change (with an older sync count) conflicts with a remote change (older, but with a more recent sync count). To avoid this conflict, update the local records meta data during the first push. This means that on a subsequent push, there will not be a data conflict exception, and ultimately there will not be a conflict-with-self where the sync counts reflect the opposite of what is actually true in terms of data recency. The goal is to make it look like the put operation succeeded, wrote the remote record to local storage, and *then* performed the update (instead of performing the update before the put send/receive had a chance to finish).
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PR merged, thanks for the contribution. |
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In the case where only some of the records in a patch are skipped by
ConditionallyPutRecords, maxPatchSyncCount will not cause the dataset sync count to be reset sufficiently to correct the skipped records when they experience aDataConflictExceptionon future sync attempts. (Especially likely if multiple records are always updated together.)Another possibility for this might be to have
ConditionallyPutRecordsreturn a flag for whether it skipped any records, and if it did, to not update the dataset sync count in theDataConflictExceptionhandler.Attempts to address issue #391