When a process joins a cluster it fetches the cluster
interface. However, not the whole interface is exposed
to the client. This mechanism relies on the fact that
the serializer keeps the field ordering and doesn't
verify the message before parsing it.
To make this work, we provide a client type with one
member (the ClusterInterface which is exposed to the
client and the server). This client interface has the
same FileIdentifier as the ClusterControllerFullInterface
which has the same first member. This works because
FlatBuffers allows for members to be missing.
A client will always try to connect all coordinators.
This commit let Status track the number of connected coordinators
for each client.
This allows us to do canary in coordinators. For example,
when we switch from non-TLS to TLS, we can switch 1 coordinator
from non-TLS to TLS. This can help check if a client has the ability
to connect through TLS.
We can make the non-TLS to TLS switch for each coordinators
one by one. This avoid the risk of losing connection in the switch.
Remove the use of relative paths. A header at foo/bar.h could be included by
files under foo/ with "bar.h", but would be included everywhere else as
"foo/bar.h". Adjust so that every include references such a header with the
latter form.
Signed-off-by: Robert Escriva <rescriva@dropbox.com>
