[CI SKIP] Refactored project layout per Mark Wolfe Blog : https://www.wolfe.id.au/2020/03/10/how-do-i-structure-my-go-project/

internal/router/router.go

@@ -0,0 +1,91 @@
+package router
+
+import (
+	"fmt"
+	"log"
+
+	gs "git.dragonheim.net/dragonheim/gagent/src/gstructs"
+
+	zmq "github.com/pebbe/zmq4"
+)
+
+// @TODO -- This was documented in the example, and I am unclear what it does
+const (
+	WORKER_READY = "\001" //  Signals worker is ready
+)
+
+// Main is the initiation function for a Router
+func Main(config gs.GagentConfig) {
+	log.Printf("[INFO] Starting router\n")
+
+	clientSock, _ := zmq.NewSocket(zmq.ROUTER)
+	defer clientSock.Close()
+
+	workerSock, _ := zmq.NewSocket(zmq.DEALER)
+	defer workerSock.Close()
+
+	clientSock.Bind(fmt.Sprintf("tcp://%s:%d", config.ListenAddr, config.ClientPort))
+	workerSock.Bind(fmt.Sprintf("tcp://%s:%d", config.ListenAddr, config.WorkerPort))
+
+	workers := make([]string, 0)
+
+	poller1 := zmq.NewPoller()
+	poller1.Add(workerSock, zmq.POLLIN)
+
+	poller2 := zmq.NewPoller()
+	poller2.Add(workerSock, zmq.POLLIN)
+	poller2.Add(clientSock, zmq.POLLIN)
+
+LOOP:
+	for {
+		//  Poll frontend only if we have available workers
+		var sockets []zmq.Polled
+		var err error
+		if len(workers) > 0 {
+			sockets, err = poller2.Poll(-1)
+		} else {
+			sockets, err = poller1.Poll(-1)
+		}
+		if err != nil {
+			break //  Interrupted
+		}
+		for _, socket := range sockets {
+			switch s := socket.Socket; s {
+			case workerSock: //  Handle worker activity on backend
+				//  Use worker identity for load-balancing
+				msg, err := s.RecvMessage(0)
+				if err != nil {
+					break LOOP //  Interrupted
+				}
+				var identity string
+				identity, msg = unwrap(msg)
+				log.Printf("[DEBUG] Worker message received: %s", msg)
+				workers = append(workers, identity)
+
+				//  Forward message to client if it's not a READY
+				if msg[0] != WORKER_READY {
+					clientSock.SendMessage(msg)
+				}
+
+			case clientSock:
+				//  Get client request, route to first available worker
+				msg, err := s.RecvMessage(0)
+				log.Printf("[DEBUG] Client message received: %s", msg)
+				if err == nil {
+					workerSock.SendMessage(workers[0], "", msg)
+					workers = workers[1:]
+				}
+			}
+		}
+	}
+}
+
+func unwrap(msg []string) (head string, tail []string) {
+	head = msg[0]
+	if len(msg) > 1 && msg[1] == "" {
+		tail = msg[2:]
+	} else {
+		tail = msg[1:]
+	}
+	return
+}