Adopt parsers in Filebeat's journald input (#29070)

One test is added that runs Filebeat reading from a journald file, it
only tests one parser, however that should be enough to ensure parsers
are supported on journald input.

Splits from #26130

CHANGELOG.next.asciidoc

@@ -345,6 +345,7 @@ https://github.com/elastic/beats/compare/v7.0.0-alpha2...master[Check the HEAD d
 - Add support in aws-s3 input for s3 notification from SNS to SQS. {pull}28800[28800]
 - Add support in aws-s3 input for custom script parsing of s3 notifications. {pull}28946[28946]
 - Improve error handling in aws-s3 input for malformed s3 notifications. {issue}28828[28828] {pull}28946[28946]
+- Add support for parsers on journald input {pull}29070[29070]
 
 *Heartbeat*
 

filebeat/_meta/config/filebeat.inputs.reference.yml.tmpl

@@ -559,3 +559,22 @@ filebeat.inputs:
   # Configure stream to filter to a specific stream: stdout, stderr or all (default)
   #stream: all
 
+#------------------------------ Journald input --------------------------------
+# Journald input is experimental.
+#- type: journald
+  #enabled: true
+  #id: service-foo
+
+  # You may wish to have separate inputs for each service. You can use
+  # include_matches to specify a list of filter expressions that are
+  # applied as a logical OR. You may specify filter
+  #include_matches:
+    #- _SYSTEMD_UNIT=foo.service
+
+  # Parsers are also supported, here is an example of the multiline
+  # parser.
+  #parsers:
+  #- multiline:
+    #type: count
+    #count_lines: 3
+

filebeat/filebeat.reference.yml

@@ -966,6 +966,25 @@ filebeat.inputs:
   # Configure stream to filter to a specific stream: stdout, stderr or all (default)
   #stream: all
 
+#------------------------------ Journald input --------------------------------
+# Journald input is experimental.
+#- type: journald
+  #enabled: true
+  #id: service-foo
+
+  # You may wish to have separate inputs for each service. You can use
+  # include_matches to specify a list of filter expressions that are
+  # applied as a logical OR. You may specify filter
+  #include_matches:
+    #- _SYSTEMD_UNIT=foo.service
+
+  # Parsers are also supported, here is an example of the multiline
+  # parser.
+  #parsers:
+  #- multiline:
+    #type: count
+    #count_lines: 3
+
 
 # =========================== Filebeat autodiscover ============================
 

filebeat/input/journald/config.go

@@ -26,6 +26,7 @@ import (
 
 	"github.com/elastic/beats/v7/filebeat/input/journald/pkg/journalfield"
 	"github.com/elastic/beats/v7/filebeat/input/journald/pkg/journalread"
+	"github.com/elastic/beats/v7/libbeat/reader/parser"
 )
 
 // Config stores the options of a journald input.
@@ -51,6 +52,9 @@ type config struct {
 
 	// SaveRemoteHostname defines if the original source of the entry needs to be saved.
 	SaveRemoteHostname bool `config:"save_remote_hostname"`
+
+	// Parsers configuration
+	Parsers parser.Config `config:",inline"`
 }
 
 var errInvalidSeekFallback = errors.New("invalid setting for cursor_seek_fallback")

filebeat/input/journald/environment_test.go

@@ -0,0 +1,286 @@
+// Licensed to Elasticsearch B.V. under one or more contributor
+// license agreements. See the NOTICE file distributed with
+// this work for additional information regarding copyright
+// ownership. Elasticsearch B.V. licenses this file to you under
+// the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+//go:build linux && cgo && withjournald
+// +build linux,cgo,withjournald
+
+package journald
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"path/filepath"
+	"sync"
+	"testing"
+	"time"
+
+	input "github.com/elastic/beats/v7/filebeat/input/v2"
+	v2 "github.com/elastic/beats/v7/filebeat/input/v2"
+	"github.com/elastic/beats/v7/libbeat/beat"
+	"github.com/elastic/beats/v7/libbeat/common"
+	"github.com/elastic/beats/v7/libbeat/common/acker"
+	"github.com/elastic/beats/v7/libbeat/logp"
+	"github.com/elastic/beats/v7/libbeat/statestore"
+	"github.com/elastic/beats/v7/libbeat/statestore/storetest"
+	"github.com/elastic/go-concert/unison"
+)
+
+type inputTestingEnvironment struct {
+	t          *testing.T
+	workingDir string
+	stateStore *testInputStore
+	pipeline   *mockPipelineConnector
+
+	pluginInitOnce sync.Once
+	plugin         v2.Plugin
+
+	wg  sync.WaitGroup
+	grp unison.TaskGroup
+}
+
+func newInputTestingEnvironment(t *testing.T) *inputTestingEnvironment {
+	return &inputTestingEnvironment{
+		t:          t,
+		workingDir: t.TempDir(),
+		stateStore: openTestStatestore(),
+		pipeline:   &mockPipelineConnector{},
+	}
+}
+
+func (e *inputTestingEnvironment) getManager() v2.InputManager {
+	e.pluginInitOnce.Do(func() {
+		e.plugin = Plugin(logp.L(), e.stateStore)
+	})
+	return e.plugin.Manager
+}
+
+func (e *inputTestingEnvironment) mustCreateInput(config map[string]interface{}) v2.Input {
+	e.t.Helper()
+	e.grp = unison.TaskGroup{}
+	manager := e.getManager()
+	if err := manager.Init(&e.grp, v2.ModeRun); err != nil {
+		e.t.Fatalf("failed to initialise manager: %+v", err)
+	}
+
+	c := common.MustNewConfigFrom(config)
+	inp, err := manager.Create(c)
+	if err != nil {
+		e.t.Fatalf("failed to create input using manager: %+v", err)
+	}
+
+	return inp
+}
+
+func (e *inputTestingEnvironment) startInput(ctx context.Context, inp v2.Input) {
+	e.wg.Add(1)
+	go func(wg *sync.WaitGroup, grp *unison.TaskGroup) {
+		defer wg.Done()
+		defer grp.Stop()
+
+		inputCtx := input.Context{Logger: logp.L(), Cancelation: ctx}
+		inp.Run(inputCtx, e.pipeline)
+	}(&e.wg, &e.grp)
+}
+
+// waitUntilEventCount waits until total count events arrive to the client.
+func (e *inputTestingEnvironment) waitUntilEventCount(count int) {
+	e.t.Helper()
+	for {
+		sum := len(e.pipeline.GetAllEvents())
+		if sum == count {
+			return
+		}
+		if count < sum {
+			e.t.Fatalf("too many events; expected: %d, actual: %d", count, sum)
+		}
+		time.Sleep(10 * time.Millisecond)
+	}
+}
+
+func (e *inputTestingEnvironment) waitUntilInputStops() {
+	e.wg.Wait()
+}
+
+func (e *inputTestingEnvironment) abspath(filename string) string {
+	return filepath.Join(e.workingDir, filename)
+}
+
+func (e *inputTestingEnvironment) mustWriteFile(filename string, lines []byte) {
+	e.t.Helper()
+	path := e.abspath(filename)
+	if err := os.WriteFile(path, lines, 0644); err != nil {
+		e.t.Fatalf("failed to write file '%s': %+v", path, err)
+	}
+}
+
+type testInputStore struct {
+	registry *statestore.Registry
+}
+
+func openTestStatestore() *testInputStore {
+	return &testInputStore{
+		registry: statestore.NewRegistry(storetest.NewMemoryStoreBackend()),
+	}
+}
+
+func (s *testInputStore) Close() {
+	s.registry.Close()
+}
+
+func (s *testInputStore) Access() (*statestore.Store, error) {
+	return s.registry.Get("filebeat")
+}
+
+func (s *testInputStore) CleanupInterval() time.Duration {
+	return 24 * time.Hour
+}
+
+type mockClient struct {
+	publishing []beat.Event
+	published  []beat.Event
+	ackHandler beat.ACKer
+	closed     bool
+	mtx        sync.Mutex
+	canceler   context.CancelFunc
+}
+
+// GetEvents returns the published events
+func (c *mockClient) GetEvents() []beat.Event {
+	c.mtx.Lock()
+	defer c.mtx.Unlock()
+
+	return c.published
+}
+
+// Publish mocks the Client Publish method
+func (c *mockClient) Publish(e beat.Event) {
+	c.PublishAll([]beat.Event{e})
+}
+
+// PublishAll mocks the Client PublishAll method
+func (c *mockClient) PublishAll(events []beat.Event) {
+	c.mtx.Lock()
+	defer c.mtx.Unlock()
+
+	c.publishing = append(c.publishing, events...)
+	for _, event := range events {
+		c.ackHandler.AddEvent(event, true)
+	}
+	c.ackHandler.ACKEvents(len(events))
+
+	for _, event := range events {
+		c.published = append(c.published, event)
+	}
+}
+
+func (c *mockClient) waitUntilPublishingHasStarted() {
+	for len(c.publishing) == 0 {
+		time.Sleep(10 * time.Millisecond)
+	}
+}
+
+// Close mocks the Client Close method
+func (c *mockClient) Close() error {
+	c.mtx.Lock()
+	defer c.mtx.Unlock()
+
+	if c.closed {
+		return fmt.Errorf("mock client already closed")
+	}
+
+	c.closed = true
+	return nil
+}
+
+// mockPipelineConnector mocks the PipelineConnector interface
+type mockPipelineConnector struct {
+	blocking bool
+	clients  []*mockClient
+	mtx      sync.Mutex
+}
+
+// GetAllEvents returns all events associated with a pipeline
+func (pc *mockPipelineConnector) GetAllEvents() []beat.Event {
+	pc.mtx.Lock()
+	defer pc.mtx.Unlock()
+
+	var evList []beat.Event
+	for _, clientEvents := range pc.clients {
+		evList = append(evList, clientEvents.GetEvents()...)
+	}
+
+	return evList
+}
+
+// Connect mocks the PipelineConnector Connect method
+func (pc *mockPipelineConnector) Connect() (beat.Client, error) {
+	return pc.ConnectWith(beat.ClientConfig{})
+}
+
+// ConnectWith mocks the PipelineConnector ConnectWith method
+func (pc *mockPipelineConnector) ConnectWith(config beat.ClientConfig) (beat.Client, error) {
+	pc.mtx.Lock()
+	defer pc.mtx.Unlock()
+
+	ctx, cancel := context.WithCancel(context.Background())
+	c := &mockClient{
+		canceler:   cancel,
+		ackHandler: newMockACKHandler(ctx, pc.blocking, config),
+	}
+
+	pc.clients = append(pc.clients, c)
+
+	return c, nil
+
+}
+
+func (pc *mockPipelineConnector) cancelAllClients() {
+	pc.mtx.Lock()
+	defer pc.mtx.Unlock()
+
+	for _, client := range pc.clients {
+		client.canceler()
+	}
+}
+
+func (pc *mockPipelineConnector) cancelClient(i int) {
+	pc.mtx.Lock()
+	defer pc.mtx.Unlock()
+
+	if len(pc.clients) < i+1 {
+		return
+	}
+
+	pc.clients[i].canceler()
+}
+
+func newMockACKHandler(starter context.Context, blocking bool, config beat.ClientConfig) beat.ACKer {
+	if !blocking {
+		return config.ACKHandler
+	}
+
+	return acker.Combine(blockingACKer(starter), config.ACKHandler)
+
+}
+
+func blockingACKer(starter context.Context) beat.ACKer {
+	return acker.EventPrivateReporter(func(acked int, private []interface{}) {
+		for starter.Err() == nil {
+		}
+	})
+}