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Doug Hoyte 2023-05-04 14:20:22 -04:00
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@ -94,7 +94,7 @@ The `IdListResponse` range contains a list of the IDs the server has (and the cl
* Because `IdList` and `IdListResponse` messages terminate processing for a given range, they are called *base case* messages.
* When the fingerprints on each side differ, the reciever should *split* its own range and send the results back in the next message. When splitting, the number of records within each sub-range should be considered. When small, an `IdList` range should be sent. When large, then the sub-range should itself be sent as a `Fingerprint` (this is the recursion).
* When a range is split, the sub-ranges should completely cover the original range's lower and upper bounds.
* How to split the range is implementation-defined. The simplest way is to divide the records that fall within the range into N equal-sized buckets, and emit an XOR-mode sub-range for each bucket. However, an implementation could choose different grouping criteria. For example, events with similar timestamps could be grouped into a single bucket. If the implementation believes the other side is less likely to have recent events, it could make the most recent bucket an `IdList`.
* How to split the range is implementation-defined. The simplest way is to divide the records that fall within the range into N equal-sized buckets, and emit a Fingerprint sub-range for each of these buckets. However, an implementation could choose different grouping criteria. For example, events with similar timestamps could be grouped into a single bucket. If the implementation believes the other side is less likely to have recent events, it could make the most recent bucket an `IdList`.
* Note that if alternate grouping strategies are used, an implementation should never reply to a range with a single `Fingerprint` range, otherwise the protocol may never terminate (if the other side does the same).
The initial message should cover the full universe, and therefore must have at least one range. The last range's upper bound should have the infinity timestamp (and the `id` doesn't matter, so should be empty also). How many ranges used in the initial message depends on the implementation. The most obvious implementation is to use the same logic as described above, either using the base case or splitting, depending on set size. However, an implementation may choose to use fewer or more buckets in its initial message, and/or may use different grouping strategies.