CloudKit extension: Tips on recovering from CKError.LimitExceeded

[heiberg]

When using YapDatabaseCloudKit, the extension will accumulate changes for upload. A change set can be arbitrarily large and will result in a single CKModifyRecordsOperation.

In some cases, for example during a database maintenance or migration operation, a significant number of objects could be modified. Resulting in a CKModifyRecordsOperation with a lot of records.

I'm seeing these operations fail with CKError.LimitExceeded, resulting in a suspended extension, and I'm currently looking for the best way to recover from this.

Without a way to break the pending change set up into smaller batches for upload, the extension will just encounter the same CKError.LimitExceeded when resumed, and sync will permanently cease to function for that particular installation.

One possible solution could be the introduction of a configurable operation batch size on the CloudKit extension. The application, or the extension itself, could reduce this when a LimitExceeded is encountered. Such a batch size would likely have to be dynamic, as the acceptable CloudKit operation size is not specified. An approach similar to the TCP protocol's exponential backoff could be used to home in on an acceptable operation size.

Is there some way to recover from this situation with the current version of YDBCK?

[SofteqDG]

Read discussion in #212.
I have also added a PR #268 with one possible solution (works fine in my app).

[heiberg]

Thanks, @SofteqDG! Excellent point about preserving CKReference integrity when splitting batches. My data model is very simple, just a pool of separate objects with no references, so your open PR was just what I needed. 👍