[8.18](backport #42462) Add status reporting for Journald input

CHANGELOG.next.asciidoc

@@ -329,6 +329,7 @@ https://github.com/elastic/beats/compare/v8.8.1\...main[Check the HEAD diff]
 - Added OAuth2 support with auto token refresh for websocket streaming input. {issue}41989[41989] {pull}42212[42212]
 - Added infinite & blanket retry options to websockets and improved logging and retry logic. {pull}42225[42225]
 - Introduce ignore older and start timestamp filters for AWS S3 input. {pull}41804[41804]
+- Journald input now can report its status to Elastic-Agent {issue}39791[39791] {pull}42462[42462]
 
 *Auditbeat*
 

filebeat/input/journald/environment_test.go

@@ -32,6 +32,7 @@ import (
 	v2 "github.com/elastic/beats/v7/filebeat/input/v2"
 	"github.com/elastic/beats/v7/libbeat/beat"
 	"github.com/elastic/beats/v7/libbeat/common/acker"
+	"github.com/elastic/beats/v7/libbeat/management/status"
 	"github.com/elastic/beats/v7/libbeat/statestore"
 	"github.com/elastic/beats/v7/libbeat/statestore/storetest"
 	conf "github.com/elastic/elastic-agent-libs/config"
@@ -40,10 +41,11 @@ import (
 )
 
 type inputTestingEnvironment struct {
-	t          *testing.T
-	workingDir string
-	stateStore *testInputStore
-	pipeline   *mockPipelineConnector
+	t              *testing.T
+	workingDir     string
+	stateStore     *testInputStore
+	pipeline       *mockPipelineConnector
+	statusReporter *mockStatusReporter
 
 	pluginInitOnce sync.Once
 	plugin         v2.Plugin
@@ -54,10 +56,11 @@ type inputTestingEnvironment struct {
 
 func newInputTestingEnvironment(t *testing.T) *inputTestingEnvironment {
 	return &inputTestingEnvironment{
-		t:          t,
-		workingDir: t.TempDir(),
-		stateStore: openTestStatestore(),
-		pipeline:   &mockPipelineConnector{},
+		t:              t,
+		workingDir:     t.TempDir(),
+		stateStore:     openTestStatestore(),
+		pipeline:       &mockPipelineConnector{},
+		statusReporter: &mockStatusReporter{},
 	}
 }
 
@@ -95,7 +98,7 @@ func (e *inputTestingEnvironment) startInput(ctx context.Context, inp v2.Input)
 			}
 		}()
 
-		inputCtx := v2.Context{Logger: logp.L(), Cancelation: ctx}
+		inputCtx := v2.Context{Logger: logp.L(), Cancelation: ctx, StatusReporter: e.statusReporter}
 		if err := inp.Run(inputCtx, e.pipeline); err != nil {
 			e.t.Errorf("input 'Run' method returned an error: %s", err)
 		}
@@ -125,6 +128,25 @@ func (e *inputTestingEnvironment) waitUntilEventCount(count int) {
 	}, 5*time.Second, 10*time.Millisecond, &msg)
 }
 
+func (e *inputTestingEnvironment) RequireStatuses(expected []statusUpdate) {
+	t := e.t
+	t.Helper()
+	got := e.statusReporter.GetUpdates()
+	if len(got) != len(expected) {
+		t.Fatalf("expecting %d updates, got %d", len(expected), len(got))
+	}
+
+	for i := range expected {
+		g, e := got[i], expected[i]
+		if g != e {
+			t.Errorf(
+				"expecting [%d] status update to be {state:%s, msg:%s}, got  {state:%s, msg:%s}",
+				i, e.state.String(), e.msg, g.state.String(), g.msg,
+			)
+		}
+	}
+}
+
 type testInputStore struct {
 	registry *statestore.Registry
 }
@@ -251,3 +273,25 @@ func blockingACKer(starter context.Context) beat.EventListener {
 		}
 	})
 }
+
+type statusUpdate struct {
+	state status.Status
+	msg   string
+}
+
+type mockStatusReporter struct {
+	mutex   sync.RWMutex
+	updates []statusUpdate
+}
+
+func (m *mockStatusReporter) UpdateStatus(status status.Status, msg string) {
+	m.mutex.Lock()
+	m.updates = append(m.updates, statusUpdate{status, msg})
+	m.mutex.Unlock()
+}
+
+func (m *mockStatusReporter) GetUpdates() []statusUpdate {
+	m.mutex.RLock()
+	defer m.mutex.RUnlock()
+	return append([]statusUpdate{}, m.updates...)
+}

filebeat/input/journald/input.go

@@ -29,6 +29,7 @@ import (
 	input "github.com/elastic/beats/v7/filebeat/input/v2"
 	cursor "github.com/elastic/beats/v7/filebeat/input/v2/input-cursor"
 	"github.com/elastic/beats/v7/libbeat/feature"
+	"github.com/elastic/beats/v7/libbeat/management/status"
 	"github.com/elastic/beats/v7/libbeat/reader"
 	"github.com/elastic/beats/v7/libbeat/reader/parser"
 	conf "github.com/elastic/elastic-agent-libs/config"
@@ -154,6 +155,8 @@ func (inp *journald) Run(
 	logger := ctx.Logger.
 		With("path", src.Name()).
 		With("input_id", inp.ID)
+
+	ctx.UpdateStatus(status.Starting, "Starting")
 	currentCheckpoint := initCheckpoint(logger, cursor)
 
 	mode := inp.Seek
@@ -173,7 +176,9 @@ func (inp *journald) Run(
 		journalctl.Factory,
 	)
 	if err != nil {
-		return fmt.Errorf("could not start journal reader: %w", err)
+		wrappedErr := fmt.Errorf("could not start journal reader: %w", err)
+		ctx.UpdateStatus(status.Failed, wrappedErr.Error())
+		return wrappedErr
 	}
 
 	defer reader.Close()
@@ -186,6 +191,7 @@ func (inp *journald) Run(
 			saveRemoteHostname: inp.SaveRemoteHostname,
 		})
 
+	ctx.UpdateStatus(status.Running, "Running")
 	for {
 		entry, err := parser.Next()
 		if err != nil {
@@ -197,14 +203,18 @@ func (inp *journald) Run(
 			case errors.Is(err, journalctl.ErrRestarting):
 				continue
 			default:
-				logger.Errorf("could not read event: %s", err)
+				msg := fmt.Sprintf("could not read event: %s", err)
+				ctx.UpdateStatus(status.Failed, msg)
+				logger.Error(msg)
 				return err
 			}
 		}
 
 		event := entry.ToEvent()
 		if err := publisher.Publish(event, event.Private); err != nil {
-			logger.Errorf("could not publish event: %s", err)
+			msg := fmt.Sprintf("could not publish event: %s", err)
+			ctx.UpdateStatus(status.Failed, msg)
+			logger.Errorf(msg)
 			return err
 		}
 	}

filebeat/input/journald/input_test.go

@@ -37,6 +37,7 @@ import (
 	"github.com/elastic/beats/v7/filebeat/input/journald/pkg/journalfield"
 	v2 "github.com/elastic/beats/v7/filebeat/input/v2"
 	"github.com/elastic/beats/v7/libbeat/beat"
+	"github.com/elastic/beats/v7/libbeat/management/status"
 	"github.com/elastic/elastic-agent-libs/logp"
 	"github.com/elastic/elastic-agent-libs/mapstr"
 )
@@ -330,6 +331,33 @@ func TestReaderAdapterCanHandleNonStringFields(t *testing.T) {
 	}
 }
 
+func TestInputCanReportStatus(t *testing.T) {
+	out := decompress(t, filepath.Join("testdata", "multiple-boots.journal.gz"))
+
+	env := newInputTestingEnvironment(t)
+	cfg := mapstr.M{
+		"paths": []string{out},
+	}
+	inp := env.mustCreateInput(cfg)
+
+	ctx, cancelInput := context.WithCancel(context.Background())
+	t.Cleanup(cancelInput)
+
+	env.startInput(ctx, inp)
+	env.waitUntilEventCount(6)
+
+	env.RequireStatuses([]statusUpdate{
+		{
+			state: status.Starting,
+			msg:   "Starting",
+		},
+		{
+			state: status.Running,
+			msg:   "Running",
+		},
+	})
+}
+
 func decompress(t *testing.T, namegz string) string {
 	t.Helper()
 

filebeat/input/v2/input.go

@@ -97,6 +97,7 @@ type Context struct {
 
 func (c Context) UpdateStatus(status status.Status, msg string) {
 	if c.StatusReporter != nil {
+		c.Logger.Debugf("updating status, status: '%s', message: '%s'", status.String(), msg)
 		c.StatusReporter.UpdateStatus(status, msg)
 	}
 }