Add information for `Manager Addresses` in the output of `docker info`

As is specified in 28018, it would be useful to know the manager's addresses
even in a worker node. This is especially useful when there are many
worker nodes in a big cluster.

The information is available in `info.Swarm.RemoteManagers`.

This fix add the information of `Manager Addresses` to the output
of `docker info`, to explicitly show it.

A test has been added for this fix.

This fix fixes 28018.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

cli/command/system/info.go

@@ -2,6 +2,7 @@ package system
 
 import (
 	"fmt"
+	"sort"
 	"strings"
 	"time"
 
@@ -131,6 +132,17 @@ func prettyPrintInfo(dockerCli *command.DockerCli, info types.Info) error {
 			}
 		}
 		fmt.Fprintf(dockerCli.Out(), " Node Address: %s\n", info.Swarm.NodeAddr)
+		managers := []string{}
+		for _, entry := range info.Swarm.RemoteManagers {
+			managers = append(managers, entry.Addr)
+		}
+		if len(managers) > 0 {
+			sort.Strings(managers)
+			fmt.Fprintf(dockerCli.Out(), " Manager Addresses:\n")
+			for _, entry := range managers {
+				fmt.Fprintf(dockerCli.Out(), "  %s\n", entry)
+			}
+		}
 	}
 
 	if len(info.Runtimes) > 0 {

integration-cli/docker_cli_swarm_test.go

@@ -1051,3 +1051,24 @@ func (s *DockerSwarmSuite) TestExtraHosts(c *check.C) {
 	c.Assert(err, checker.IsNil)
 	c.Assert(out, checker.Contains, expectedOutput, check.Commentf("Expected '%s', but got %q", expectedOutput, out))
 }
+
+func (s *DockerSwarmSuite) TestSwarmManagerAddress(c *check.C) {
+	d1 := s.AddDaemon(c, true, true)
+	d2 := s.AddDaemon(c, true, false)
+	d3 := s.AddDaemon(c, true, false)
+
+	// Manager Addresses will always show Node 1's address
+	expectedOutput := fmt.Sprintf("Manager Addresses:\n  127.0.0.1:%d\n", d1.port)
+
+	out, err := d1.Cmd("info")
+	c.Assert(err, checker.IsNil)
+	c.Assert(out, checker.Contains, expectedOutput)
+
+	out, err = d2.Cmd("info")
+	c.Assert(err, checker.IsNil)
+	c.Assert(out, checker.Contains, expectedOutput)
+
+	out, err = d3.Cmd("info")
+	c.Assert(err, checker.IsNil)
+	c.Assert(out, checker.Contains, expectedOutput)
+}