Incorporating review comments

CHANGELOG.asciidoc

@@ -161,6 +161,7 @@ https://github.com/elastic/beats/compare/v6.2.3...master[Check the HEAD diff]
 - Add experimental Jolokia Discovery autodiscover provider. {pull}7141[7141]
 - Add owner object info to Kubernetes metadata. {pull}7231[7231]
 - Add beat export dashboard command. {pull}7239[7239]
+- Add support for docker autodiscover to monitor containers on host network {pull}6708[6708]
 
 *Auditbeat*
 

libbeat/autodiscover/providers/docker/docker.go

@@ -24,7 +24,6 @@ type Provider struct {
 	appenders     autodiscover.Appenders
 	watcher       docker.Watcher
 	templates     *template.Mapper
-	hostIP        string
 	stop          chan interface{}
 	startListener bus.Listener
 	stopListener  bus.Listener
@@ -66,16 +65,13 @@ func AutodiscoverBuilder(bus bus.Bus, c *common.Config) (autodiscover.Provider,
 		return nil, err
 	}
 
-	hostIP := docker.GetHostIP(watcher)
-
 	return &Provider{
 		config:        config,
 		bus:           bus,
 		builders:      builders,
 		appenders:     appenders,
 		templates:     mapper,
 		watcher:       watcher,
-		hostIP:        hostIP,
 		stop:          make(chan interface{}),
 		startListener: start,
 		stopListener:  stop,
@@ -112,10 +108,7 @@ func (d *Provider) emitContainer(event bus.Event, flag string) {
 	var host string
 	if len(container.IPAddresses) > 0 {
 		host = container.IPAddresses[0]
-	} else {
-		host = d.hostIP
 	}
-
 	labelMap := common.MapStr{}
 	for k, v := range container.Labels {
 		safemapstr.Put(labelMap, k, v)

libbeat/common/docker/watcher.go

@@ -71,13 +71,12 @@ type Container struct {
 	Labels      map[string]string
 	IPAddresses []string
 	Ports       []types.Port
-	// Only needed internally
-	gateways []string
 }
 
 // Client for docker interface
 type Client interface {
 	ContainerList(ctx context.Context, options types.ContainerListOptions) ([]types.Container, error)
+	ContainerInspect(ctx context.Context, container string) (types.ContainerJSON, error)
 	Events(ctx context.Context, options types.EventsOptions) (<-chan events.Message, <-chan error)
 }
 
@@ -291,14 +290,20 @@ func (w *watcher) listContainers(options types.ContainerListOptions) ([]*Contain
 	var result []*Container
 	for _, c := range containers {
 		var ipaddresses []string
-		var gateways []string
 		for _, net := range c.NetworkSettings.Networks {
 			if net.IPAddress != "" {
 				ipaddresses = append(ipaddresses, net.IPAddress)
 			}
+		}
 
-			if net.Gateway != "" {
-				gateways = append(gateways, net.Gateway)
+		// If there are no network interfaces, assume that the container is on host network
+		// Inspect the container directly and use the hostname as the IP address in order
+		if len(ipaddresses) == 0 {
+			info, err := w.client.ContainerInspect(w.ctx, c.ID)
+			if err == nil {
+				ipaddresses = append(ipaddresses, info.Config.Hostname)
+			} else {
+				logp.Warn("unable to inspect container %s due to error %v", c.ID, err)
 			}
 		}
 		result = append(result, &Container{
@@ -308,7 +313,6 @@ func (w *watcher) listContainers(options types.ContainerListOptions) ([]*Contain
 			Labels:      c.Labels,
 			Ports:       c.Ports,
 			IPAddresses: ipaddresses,
-			gateways:    gateways,
 		})
 	}
 

libbeat/common/docker/watcher_test.go

@@ -1,6 +1,7 @@
 package docker
 
 import (
+	"errors"
 	"testing"
 	"time"
 
@@ -46,6 +47,10 @@ func (m *MockClient) Events(ctx context.Context, options types.EventsOptions) (<
 	return eventsC, errorsC
 }
 
+func (m *MockClient) ContainerInspect(ctx context.Context, container string) (types.ContainerJSON, error) {
+	return types.ContainerJSON{}, errors.New("unimplemented")
+}
+
 func TestWatcherInitialization(t *testing.T) {
 	watcher := runWatcher(t, true,
 		[][]types.Container{