cmd/swarm: solve rare cases of using the same random port in tests (#17352)

cmd/swarm/config_test.go

@@ -20,6 +20,7 @@ import (
 	"fmt"
 	"io"
 	"io/ioutil"
+	"net"
 	"os"
 	"os/exec"
 	"testing"
@@ -559,3 +560,16 @@ func TestValidateConfig(t *testing.T) {
 		}
 	}
 }
+
+func assignTCPPort() (string, error) {
+	l, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		return "", err
+	}
+	l.Close()
+	_, port, err := net.SplitHostPort(l.Addr().String())
+	if err != nil {
+		return "", err
+	}
+	return port, nil
+}

cmd/swarm/run_test.go

@@ -17,12 +17,15 @@
 package main
 
 import (
+	"context"
 	"fmt"
 	"io/ioutil"
 	"net"
 	"os"
 	"path/filepath"
 	"runtime"
+	"sync"
+	"syscall"
 	"testing"
 	"time"
 
@@ -218,14 +221,12 @@ func existingTestNode(t *testing.T, dir string, bzzaccount string) *testNode {
 	}
 
 	// assign ports
-	httpPort, err := assignTCPPort()
-	if err != nil {
-		t.Fatal(err)
-	}
-	p2pPort, err := assignTCPPort()
+	ports, err := getAvailableTCPPorts(2)
 	if err != nil {
 		t.Fatal(err)
 	}
+	p2pPort := ports[0]
+	httpPort := ports[1]
 
 	// start the node
 	node.Cmd = runSwarm(t,
@@ -246,6 +247,17 @@ func existingTestNode(t *testing.T, dir string, bzzaccount string) *testNode {
 		}
 	}()
 
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+	defer cancel()
+
+	// ensure that all ports have active listeners
+	// so that the next node will not get the same
+	// when calling getAvailableTCPPorts
+	err = waitTCPPorts(ctx, ports...)
+	if err != nil {
+		t.Fatal(err)
+	}
+
 	// wait for the node to start
 	for start := time.Now(); time.Since(start) < 10*time.Second; time.Sleep(50 * time.Millisecond) {
 		node.Client, err = rpc.Dial(conf.IPCEndpoint())
@@ -280,14 +292,12 @@ func newTestNode(t *testing.T, dir string) *testNode {
 	node := &testNode{Dir: dir}
 
 	// assign ports
-	httpPort, err := assignTCPPort()
-	if err != nil {
-		t.Fatal(err)
-	}
-	p2pPort, err := assignTCPPort()
+	ports, err := getAvailableTCPPorts(2)
 	if err != nil {
 		t.Fatal(err)
 	}
+	p2pPort := ports[0]
+	httpPort := ports[1]
 
 	// start the node
 	node.Cmd = runSwarm(t,
@@ -308,6 +318,17 @@ func newTestNode(t *testing.T, dir string) *testNode {
 		}
 	}()
 
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+	defer cancel()
+
+	// ensure that all ports have active listeners
+	// so that the next node will not get the same
+	// when calling getAvailableTCPPorts
+	err = waitTCPPorts(ctx, ports...)
+	if err != nil {
+		t.Fatal(err)
+	}
+
 	// wait for the node to start
 	for start := time.Now(); time.Since(start) < 10*time.Second; time.Sleep(50 * time.Millisecond) {
 		node.Client, err = rpc.Dial(conf.IPCEndpoint())
@@ -343,15 +364,92 @@ func (n *testNode) Shutdown() {
 	}
 }
 
-func assignTCPPort() (string, error) {
-	l, err := net.Listen("tcp", "127.0.0.1:0")
-	if err != nil {
-		return "", err
+// getAvailableTCPPorts returns a set of ports that
+// nothing is listening on at the time.
+//
+// Function assignTCPPort cannot be called in sequence
+// and guardantee that the same port will be returned in
+// different calls as the listener is closed within the function,
+// not after all listeners are started and selected unique
+// available ports.
+func getAvailableTCPPorts(count int) (ports []string, err error) {
+	for i := 0; i < count; i++ {
+		l, err := net.Listen("tcp", "127.0.0.1:0")
+		if err != nil {
+			return nil, err
+		}
+		// defer close in the loop to be sure the same port will not
+		// be selected in the next iteration
+		defer l.Close()
+
+		_, port, err := net.SplitHostPort(l.Addr().String())
+		if err != nil {
+			return nil, err
+		}
+		ports = append(ports, port)
+	}
+	return ports, nil
+}
+
+// waitTCPPorts blocks until tcp connections can be
+// established on all provided ports. It runs all
+// ports dialers in parallel, and returns the first
+// encountered error.
+// See waitTCPPort also.
+func waitTCPPorts(ctx context.Context, ports ...string) error {
+	var err error
+	// mu locks err variable that is assigned in
+	// other goroutines
+	var mu sync.Mutex
+
+	// cancel is canceling all goroutines
+	// when the firs error is returned
+	// to prevent unnecessary waiting
+	ctx, cancel := context.WithCancel(ctx)
+	defer cancel()
+
+	var wg sync.WaitGroup
+	for _, port := range ports {
+		wg.Add(1)
+		go func(port string) {
+			defer wg.Done()
+
+			e := waitTCPPort(ctx, port)
+
+			mu.Lock()
+			defer mu.Unlock()
+			if e != nil && err == nil {
+				err = e
+				cancel()
+			}
+		}(port)
+	}
+	wg.Wait()
+
+	return err
+}
+
+// waitTCPPort blocks until tcp connection can be established
+// ona provided port. It has a 3 minute timeout as maximum,
+// to prevent long waiting, but it can be shortened with
+// a provided context instance. Dialer has a 10 second timeout
+// in every iteration, and connection refused error will be
+// retried in 100 milliseconds periods.
+func waitTCPPort(ctx context.Context, port string) error {
+	ctx, cancel := context.WithTimeout(ctx, 3*time.Minute)
+	defer cancel()
+
+	for {
+		c, err := (&net.Dialer{Timeout: 10 * time.Second}).DialContext(ctx, "tcp", "127.0.0.1:"+port)
+		if err != nil {
+			if operr, ok := err.(*net.OpError); ok {
+				if syserr, ok := operr.Err.(*os.SyscallError); ok && syserr.Err == syscall.ECONNREFUSED {
+					time.Sleep(100 * time.Millisecond)
+					continue
+				}
+			}
+			return err
+		}
+		return c.Close()
 	}
-	l.Close()
-	_, port, err := net.SplitHostPort(l.Addr().String())
-	if err != nil {
-		return "", err
-	}
-	return port, nil
 }