Define interface for mutable and immutable messages

transport/message.go

@@ -0,0 +1,49 @@
+package transport
+
+import "io"
+
+// ImmutableMessage defines an interface for read-only messages received by a
+// Transport.
+type ImmutableMessage interface {
+	// ImmutableMessage implements io.Closer. All messages should be closed
+	// when they are no longer being used.
+	io.Closer
+
+	// Sender returns the name of the service that sent the mesage.
+	Sender() string
+
+	// Receiver returns the name of the service that will receive the message.
+	Receiver() string
+
+	// Endpoint returns the receiving service endpoint where the message
+	// will be routed to. The receiving service name combined with the
+	// endpoint name should be unique among all running services.
+	Endpoint() string
+
+	// Headers returns a map of header values associated with the message.
+	Headers() map[string]string
+
+	// Payload returns the payload associated with the message as a byte
+	// slice or an error if one is encoded in the message.
+	Payload() ([]byte, error)
+}
+
+// Message defines an interface for messages whose headers and payload can be
+// modified by the sender. Message instances are typically used by clients to
+// send RPC requests or by servers to respond to incoming messages.
+type Message interface {
+	ImmutableMessage
+
+	// SetPayload sets the content of this message. The content may be either
+	// a byte slice or an error message.
+	SetPayload(payload []byte, err error)
+
+	// SetHeader sets the content of a message header to the specified value.
+	// If the specified header already exists, its value will be overwritten
+	// by the new value.
+	SetHeader(name, value string)
+
+	// SetHeaders sets the contents of a batch of headers. This is equivalent
+	// to iterating the map and calling SetHeader for each key/value.
+	SetHeaders(headers map[string]string)
+}