Merge pull request 'cluster: initial import' (#332) from cluster into v3

Reviewed-on: #332

cluster/cluster.go

@@ -0,0 +1,41 @@
+package cluster
+
+import (
+	"context"
+
+	"go.unistack.org/micro/v3/metadata"
+)
+
+// Message sent to member in cluster
+type Message interface {
+	// Header returns message headers
+	Header() metadata.Metadata
+	// Body returns broker message may be []byte slice or some go struct or interface
+	Body() interface{}
+}
+
+type Node interface {
+	// Name returns node name
+	Name() string
+	// Address returns node address
+	Address() string
+	// Metadata returns node metadata
+	Metadata() metadata.Metadata
+}
+
+// Cluster interface used for cluster communication across nodes
+type Cluster interface {
+	// Join is used to take an existing members and performing state sync
+	Join(ctx context.Context, addr ...string) error
+	// Leave broadcast a leave message and stop listeners
+	Leave(ctx context.Context) error
+	// Ping is used to probe live status of the node
+	Ping(ctx context.Context, node Node, payload []byte) error
+	// Members returns the cluster members
+	Members() ([]Node, error)
+	// Broadcast send message for all members in cluster, if filter is not nil, nodes may be filtered
+	// by key/value pairs
+	Broadcast(ctx context.Context, msg Message, filter ...string) error
+	// Unicast send message to single member in cluster
+	Unicast(ctx context.Context, node Node, msg Message) error
+}