basic ranged auto listener (#779)

agent/agent.go

@@ -18,15 +18,16 @@ import (
 )
 
 type Agent struct {
-	cfg         *AgentConfig
-	root        env_core.Root
-	agentSocket string
-	shares      map[string]*share
-	addShare    chan *share
-	rmShare     chan *share
-	accesses    map[string]*access
-	addAccess   chan *access
-	rmAccess    chan *access
+	cfg          *AgentConfig
+	httpEndpoint string
+	root         env_core.Root
+	agentSocket  string
+	shares       map[string]*share
+	addShare     chan *share
+	rmShare      chan *share
+	accesses     map[string]*access
+	addAccess    chan *access
+	rmAccess     chan *access
 }
 
 func NewAgent(cfg *AgentConfig, root env_core.Root) (*Agent, error) {
@@ -109,7 +110,13 @@ func (a *Agent) gateway(cfg *AgentConfig) {
 		logrus.Fatalf("unable to register gateway: %v", err)
 	}
 
-	if err := http.ListenAndServe(cfg.ConsoleEndpoint, agentUi.Middleware(mux)); err != nil {
+	listener, err := AutoListener(cfg.ConsoleAddress, cfg.ConsoleStartPort, cfg.ConsoleEndPort)
+	if err != nil {
+		logrus.Fatalf("unable to create a listener: %v", err)
+	}
+	a.httpEndpoint = listener.Addr().String()
+
+	if err := http.Serve(listener, agentUi.Middleware(mux)); err != nil {
 		logrus.Error(err)
 	}
 }

agent/autoListener.go

@@ -0,0 +1,17 @@
+package agent
+
+import (
+	"fmt"
+	"net"
+)
+
+func AutoListener(address string, startPort, endPort uint16) (net.Listener, error) {
+	for i := startPort; i <= endPort; i++ {
+		l, err := net.Listen("tcp", fmt.Sprintf("%s:%d", address, i))
+		if err != nil {
+			continue
+		}
+		return l, nil
+	}
+	return nil, fmt.Errorf("no listener found in range")
+}

agent/config.go

@@ -1,11 +1,15 @@
 package agent
 
 type AgentConfig struct {
-	ConsoleEndpoint string
+	ConsoleAddress   string
+	ConsoleStartPort uint16
+	ConsoleEndPort   uint16
 }
 
-func DefaultAgentConfig() *AgentConfig {
+func DefaultConfig() *AgentConfig {
 	return &AgentConfig{
-		ConsoleEndpoint: "127.0.0.1:8888",
+		ConsoleAddress:   "127.0.0.1",
+		ConsoleStartPort: 8080,
+		ConsoleEndPort:   8181,
 	}
 }

agent/version.go

@@ -12,6 +12,6 @@ func (i *agentGrpcImpl) Version(_ context.Context, _ *agentGrpc.VersionRequest)
 	logrus.Debugf("responding to version inquiry with '%v'", v)
 	return &agentGrpc.VersionResponse{
 		V:               v,
-		ConsoleEndpoint: i.agent.Config().ConsoleEndpoint,
+		ConsoleEndpoint: i.agent.httpEndpoint,
 	}, nil
 }