[FAB-11082] bubble errors up to main

 - fabproxy construction now panics on programmer error
 - fabproxy start errors are printed

Change-Id: I0bff8dc807e56441291ed20a31fade1e4f99c2bf
Signed-off-by: Morgan Bauer <mbauer@us.ibm.com>

fabproxy/cmd/main.go

@@ -72,7 +72,11 @@ func main() {
 
 	fmt.Printf("Starting Fab Proxy on port %d\n", portNumber)
 	proxy := fabproxy.NewFabProxy(ethService)
-	proxy.Start(portNumber)
+	err = proxy.Start(portNumber)
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
 	defer func() {
 		fmt.Println("Shutting down the Fab Proxy")
 		proxy.Shutdown()

fabproxy/fabproxy.go

@@ -29,12 +29,17 @@ func NewFabProxy(service EthService) *FabProxy {
 	}
 
 	rpcServer.RegisterCodec(NewRPCCodec(), "application/json")
-	rpcServer.RegisterService(service, "eth")
-	rpcServer.RegisterService(&NetService{}, "net")
+	msg := "this panic indicates a programming error, and is unreachable"
+	if err := rpcServer.RegisterService(service, "eth"); err != nil {
+		panic(msg)
+	}
+	if err := rpcServer.RegisterService(&NetService{}, "net"); err != nil {
+		panic(msg)
+	}
 	return proxy
 }
 
-func (p *FabProxy) Start(port int) {
+func (p *FabProxy) Start(port int) error {
 	r := mux.NewRouter()
 	r.Handle("/", p.rpcServer)
 
@@ -43,7 +48,7 @@ func (p *FabProxy) Start(port int) {
 	allowedMethods := handlers.AllowedMethods([]string{"POST"})
 
 	p.httpServer = &http.Server{Handler: handlers.CORS(allowedHeaders, allowedOrigins, allowedMethods)(r), Addr: fmt.Sprintf(":%d", port)}
-	fmt.Println(p.httpServer.ListenAndServe())
+	return p.httpServer.ListenAndServe()
 }
 
 func (p *FabProxy) Shutdown() error {

fabproxy/fabproxy_test.go

@@ -12,6 +12,7 @@ import (
 	"io/ioutil"
 	"net"
 	"net/http"
+	"strconv"
 	"strings"
 
 	"github.com/hyperledger/fabric-chaincode-evm/fabproxy"
@@ -31,15 +32,18 @@ var _ = Describe("Fabproxy", func() {
 		req            *http.Request
 		proxyDoneChan  chan struct{}
 		client         *http.Client
+		port           int
 	)
 
 	BeforeEach(func() {
-		port := config.GinkgoConfig.ParallelNode + 5000
+		port = config.GinkgoConfig.ParallelNode + 5000
 		mockEthService = &mocks.MockEthService{}
 		client = &http.Client{}
 
 		proxyDoneChan = make(chan struct{}, 1)
+		var err error
 		proxy = fabproxy.NewFabProxy(mockEthService)
+		Expect(err).ToNot(HaveOccurred())
 
 		go func(proxy *fabproxy.FabProxy, proxyDoneChan chan struct{}) {
 			proxy.Start(port)
@@ -65,7 +69,6 @@ var _ = Describe("Fabproxy", func() {
 		}
 
 		//curl -X POST --data '{"jsonrpc":"2.0","method":"eth_getCode","params":["0xa94f5374fce5edbc8e2a8697c15331677e6ebf0b", "0x2"],"id":1}'
-		var err error
 		body := strings.NewReader(`{"jsonrpc":"2.0","method":"eth_getCode","params":["0xa94f5374fce5edbc8e2a8697c15331677e6ebf0b"],"id":1}`)
 		req, err = http.NewRequest("POST", proxyAddr, body)
 		Expect(err).ToNot(HaveOccurred())
@@ -167,3 +170,35 @@ var _ = Describe("Fabproxy", func() {
 		})
 	})
 })
+
+var _ = Describe("fabproxy fails to start", func() {
+	var (
+		ln  net.Listener
+		err error
+	)
+	Context("when the port is already bound", func() {
+
+		port := config.GinkgoConfig.ParallelNode + 5000
+		portstr := strconv.Itoa(port)
+
+		BeforeEach(func() {
+			By("binds the port " + portstr)
+			ln, err = net.Listen("tcp", ":"+portstr)
+			Expect(err).ToNot(HaveOccurred())
+		})
+
+		mockEthService := &mocks.MockEthService{}
+		proxy := fabproxy.NewFabProxy(mockEthService)
+
+		It("exits instead of starting", func() {
+			err := proxy.Start(port)
+			Expect(err).To(HaveOccurred())
+		})
+
+		AfterEach(func() {
+			By("releasing the port")
+			err := ln.Close()
+			Expect(err).ToNot(HaveOccurred())
+		})
+	})
+})