This change allows the read request to specify the maximum time the node
receiving the request may have last heard from the cluster leader. It
only applies to a read consistency selection of None.
A non-voting node doesn't participate in Raft consensus, but does
subscribe to the committed log entries originating with the leader.
This means a non-voting node keeps up-to-date with the state machine,
without impacting write-latency. These non-voting nodes can provide
read scalability for the cluster.
With this change the cluster metadata (arbitrary key-value data associated with each node) is now broadcast across the cluster using the standard consensus mechanism. Specifically the use case for this metadata is to allow all nodes know the HTTP API address of all other nodes, for the purpose of redirecting requests to the leader.
This change removed the need for multiplexing two logical connections
over the single Raft TCP connection, which greatly simplifies the
networking code generally.
Original PR https://github.com/rqlite/rqlite/pull/434
The Query() and Execute() functions on the Store now take a complex type
that encapsulates the statements, and associated parameters. This will
make it easier to add more control parameters when making requests.
The main rqlite code needs this logic to check if the Discovery Service
should even be accessed. This code makes assumptions about how the Raft
module works, which is subject to change. The new unit tests should
capture that.
Philip O'Toole
wangfenjin
WanliTian