The patch series introduces linearisable topology changes using
raft protocol. The state machine driven by raft is described in
"service: Introduce topology state machine". Some explanations about
the implementation can be found in "storage_service: raft topology:
implement topology management through raft".
The code is not ready for production. There is not much in terms of error
handling and integration with the rest of the system is not even started.
For full integration request fencing will need to be implemented and
token_metadata has to be extended to support not just "pending" nodes
but concepts of "read replica set" and "write replica set".
The code may be far from be usable, but it is hidden behind the
"experimental raft" flag and having it in tree will relieve me from
constant rebase burden.
* 'raft-topology-v6' of github.com:scylladb/scylla-dev:
storage_service: fix indentation from previous patch
storage_service: raft topology: implement topology management through raft
service: raft: make group0_guard move assignable
service: raft: wire up apply() and snapshot transfer for topology in group0 state machine
storage_service: raft topology: introduce a function that applies topology cmd to local state machine
storage_service: raft topology: introduce a raft monitor and topology coordinator fibers
storage_service: raft topology: introduce snapshot transfer code for the topology table
raft topology: add RAFT_TOPOLOGY_CMD verb that will be used by topology coordinator to communicated with nodes
bootstrapper: Add get_random_bootstrap_tokens function
service: raft: add support for topology_change command into raft_group0_client
service: raft: introduce topology_change group0 command
system_keyspace: add a table to persist topology change state machine's state
service: Introduce topology state machine data structures
storage_proxy: not consult topology on local table write
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