ipfs-cluster-service now has a migration subcommand that upgrades
persistant state snapshots with an out-of-date format version to the
newest version of raft state. If all cluster members shutdown with
consistent state, upgrade ipfs-cluster, and run the state upgrade command,
the new version of cluster will be compatible with persistent storage.
ipfs-cluster now validates its persistent state upon loading it and exits
with a clear error in the case the state format version is not up to date.
Raft snapshotting is enforced on all shutdowns and the json backup is no
longer run. This commit makes use of recent changes to libp2p-raft
allowing raft states to implement their own marshaling strategies. Now
mapstate handles the logic for its (de)serialization. In the interest of
supporting various potential upgrade formats the state serialization
begins with a varint (right now one byte) describing the version.
Some go tests are modified and a go test is added to cover new ipfs-cluster
raft snapshot reading functions. Sharness tests are added to cover the
state upgrade command.
