Emit events for docker daemon

This fix tries to cover the issue raised in #22463 by emitting
events for docker daemon so that user could be notified by
scenarios like config reload, etc.

This fix adds the `daemon reload`, and events for docker daemon.

Additional tests have been added to cover the changes in this fix.

This fix fixes #22463.

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

daemon/daemon.go

@@ -6,6 +6,7 @@
 package daemon
 
 import (
+	"encoding/json"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -1337,6 +1338,11 @@ func (daemon *Daemon) initDiscovery(config *Config) error {
 func (daemon *Daemon) Reload(config *Config) error {
 	daemon.configStore.reloadLock.Lock()
 	defer daemon.configStore.reloadLock.Unlock()
+
+	if err := daemon.reloadClusterDiscovery(config); err != nil {
+		return err
+	}
+
 	if config.IsValueSet("labels") {
 		daemon.configStore.Labels = config.Labels
 	}
@@ -1370,7 +1376,26 @@ func (daemon *Daemon) Reload(config *Config) error {
 		daemon.uploadManager.SetConcurrency(*daemon.configStore.MaxConcurrentUploads)
 	}
 
-	return daemon.reloadClusterDiscovery(config)
+	// We emit daemon reload event here with updatable configurations
+	attributes := map[string]string{}
+	attributes["debug"] = fmt.Sprintf("%t", daemon.configStore.Debug)
+	attributes["cluster-store"] = daemon.configStore.ClusterStore
+	if daemon.configStore.ClusterOpts != nil {
+		opts, _ := json.Marshal(daemon.configStore.ClusterOpts)
+		attributes["cluster-store-opts"] = string(opts)
+	} else {
+		attributes["cluster-store-opts"] = "{}"
+	}
+	attributes["cluster-advertise"] = daemon.configStore.ClusterAdvertise
+	if daemon.configStore.Labels != nil {
+		labels, _ := json.Marshal(daemon.configStore.Labels)
+		attributes["labels"] = string(labels)
+	} else {
+		attributes["labels"] = "[]"
+	}
+	daemon.LogDaemonEventWithAttributes("reload", attributes)
+
+	return nil
 }
 
 func (daemon *Daemon) reloadClusterDiscovery(config *Config) error {

daemon/events.go

@@ -80,6 +80,17 @@ func (daemon *Daemon) LogNetworkEventWithAttributes(nw libnetwork.Network, actio
 	daemon.EventsService.Log(action, events.NetworkEventType, actor)
 }
 
+// LogDaemonEventWithAttributes generates an event related to the daemon itself with specific given attributes.
+func (daemon *Daemon) LogDaemonEventWithAttributes(action string, attributes map[string]string) {
+	if daemon.EventsService != nil {
+		actor := events.Actor{
+			ID:         daemon.ID,
+			Attributes: attributes,
+		}
+		daemon.EventsService.Log(action, events.DaemonEventType, actor)
+	}
+}
+
 // SubscribeToEvents returns the currently record of events, a channel to stream new events from, and a function to cancel the stream of events.
 func (daemon *Daemon) SubscribeToEvents(since, until time.Time, filter filters.Args) ([]events.Message, chan interface{}) {
 	ef := daemonevents.NewFilter(filter)

docs/reference/api/docker_remote_api.md

@@ -119,6 +119,7 @@ This section lists each version from latest to oldest.  Each listing includes a
 * `POST /containers/create` now returns a HTTP 400 "bad parameter" message
   if no command is specified (instead of a HTTP 500 "server error")
 * `GET /images/search` now takes a `filters` query parameter.
+* `GET /events` now supports daemon events of `reload`.
 
 ### v1.23 API changes
 

docs/reference/api/docker_remote_api_v1.24.md

@@ -2420,6 +2420,10 @@ Docker networks report the following events:
 
     create, connect, disconnect, destroy
 
+Docker daemon report the following event:
+
+    reload
+
 **Example request**:
 
     GET /events?since=1374067924

docs/reference/commandline/events.md

@@ -35,6 +35,10 @@ Docker networks report the following events:
 
     create, connect, disconnect, destroy
 
+Docker daemon report the following events:
+
+    reload
+
 The `--since` and `--until` parameters can be Unix timestamps, date formatted
 timestamps, or Go duration strings (e.g. `10m`, `1h30m`) computed
 relative to the client machine’s time. If you do not provide the `--since` option,

integration-cli/docker_cli_events_unix_test.go

@@ -9,6 +9,7 @@ import (
 	"os"
 	"os/exec"
 	"strings"
+	"syscall"
 	"time"
 	"unicode"
 
@@ -366,3 +367,44 @@ func (s *DockerSuite) TestEventsFilterNetworkID(c *check.C) {
 	c.Assert(events[0], checker.Contains, "test-event-network-local")
 	c.Assert(events[0], checker.Contains, "type=bridge")
 }
+
+func (s *DockerDaemonSuite) TestDaemonEvents(c *check.C) {
+	testRequires(c, SameHostDaemon, DaemonIsLinux)
+
+	// daemon config file
+	configFilePath := "test.json"
+	configFile, err := os.Create(configFilePath)
+	c.Assert(err, checker.IsNil)
+	defer os.Remove(configFilePath)
+
+	daemonConfig := `{"labels":["foo=bar"]}`
+	fmt.Fprintf(configFile, "%s", daemonConfig)
+	configFile.Close()
+	c.Assert(s.d.Start(fmt.Sprintf("--config-file=%s", configFilePath)), check.IsNil)
+
+	// Get daemon ID
+	out, err := s.d.Cmd("info")
+	c.Assert(err, checker.IsNil)
+	daemonID := ""
+	for _, line := range strings.Split(out, "\n") {
+		if strings.HasPrefix(line, "ID: ") {
+			daemonID = strings.TrimPrefix(line, "ID: ")
+			break
+		}
+	}
+	c.Assert(daemonID, checker.Not(checker.Equals), "")
+
+	configFile, err = os.Create(configFilePath)
+	c.Assert(err, checker.IsNil)
+	daemonConfig = `{"labels":["bar=foo"]}`
+	fmt.Fprintf(configFile, "%s", daemonConfig)
+	configFile.Close()
+
+	syscall.Kill(s.d.cmd.Process.Pid, syscall.SIGHUP)
+
+	time.Sleep(3 * time.Second)
+
+	out, err = s.d.Cmd("events", "--since=0", "--until", daemonUnixTime(c))
+	c.Assert(err, checker.IsNil)
+	c.Assert(out, checker.Contains, fmt.Sprintf("daemon reload %s (cluster-advertise=, cluster-store=, cluster-store-opts={}, debug=true, labels=[\"bar=foo\"])", daemonID))
+}