libnetwork agent mode is a mode where libnetwork can act as a local
agent for network and discovery plumbing alone while the state
management is done elsewhere. This completes the support for making
libnetwork and its associated drivers to be completely independent of a
k/v store(if needed) and work purely based on the state information
passed along by some some external controller or manager. This does not
mean that libnetwork support for decentralized state management via a
k/v store is removed.
Signed-off-by: Jana Radhakrishnan <mrjana@docker.com>
When a node joins a network it sends out a gossip event before it
updates it's own in-memory state. This can create a race where the node
gets the event back from a remote node before we update in-memory state
and we treat that as latest state. To avoid this race, always generate
the gossip after updating local state.
Signed-off-by: Jana Radhakrishnan <mrjana@docker.com>
Network DB is a network scoped gossip database built
on top of hashicorp/memberlist providing an eventually
consistent state store.
It limits the scope of the gossip and periodic bulk syncing
for table entries to only the nodes which participate in the
network to which the gossip belongs. This designs make the
gossip layer scale better and only consumes resources for the
network state that the node participates in.
Since the complete state for a network is maintained by all nodes
participating in the network, all nodes will eventually converge
to the same state.
NetworkDB also provides facilities for the users of the package to
watch on any table (or all tables) and get notified if there are
state changes of interest that happened anywhere in the cluster when
that state change eventually finds it's way to the watcher's node.
Signed-off-by: Jana Radhakrishnan <mrjana@docker.com>
