It takes as paramters the replication factor and the zone redundancy, computes the
largest partition size reachable with these constraints, and among the possible
assignation with this partition size, it computes the one that moves the least number
of partitions compared to the previous assignation.
This computation uses graph algorithms defined in graph_algo.rs
- change the terminology: the network configuration becomes the role
table, the configuration of a nodes becomes a node's role
- the modification of the role table takes place in two steps: first,
changes are staged in a CRDT data structure. Then, once the user is
happy with the changes, they can commit them all at once (or revert
them).
- update documentation
- fix tests
- implement smarter partition assignation algorithm
This patch breaks the format of the network configuration: when
migrating, the cluster will be in a state where no roles are assigned.
All roles must be re-assigned and commited at once. This migration
should not pose an issue.
- Explicit "replication_mode" configuration parameters that takes
either "none", "2" or "3" as values, instead of letting user configure
replication factor themselves. These are presets whose corresponding
replication/quorum values can be found in replication/mode.rs
- Explicit support for single-node and two-node deployments
(number of nodes must be at least "replication_mode", with "none"
we can have only one node)
- Ring is now stored much more compactly with 256*8 + n*32 bytes,
instead of 256*32 bytes
- Support for gateway-only nodes that do not store data
(these nodes still need a metadata_directory to store the list
of bucket and keys since those are stored on all nodes; it also
technically needs a data_directory to start but it will stay
empty unless we have bugs)
