Add tag "truncated" to "log.flags" if incoming line is longer than configured limit

CHANGELOG.asciidoc

@@ -98,6 +98,7 @@ https://github.com/elastic/beats/compare/v6.4.0...master[Check the HEAD diff]
 - Add custom unpack to log hints config to avoid env resolution {pull}7710[7710]
 - Keep raw user agent information after parsing as user_agent_raw in Filebeat modules. {pull}7823[7832]
 - Make docker input check if container strings are empty {pull}7960[7960]
+- Add tag "truncated" to "log.status" if incoming line is longer than configured limit. {pull}7991[7991]
 
 *Heartbeat*
 

filebeat/_meta/fields.common.yml

@@ -108,6 +108,10 @@
       description: >
         Logging level.
 
+    - name: log.flags
+      description: >
+        This field contains the flags of the event.
+
     - name: event.created
       type: date
       description: >

filebeat/docs/fields.asciidoc

@@ -2682,6 +2682,14 @@ type: keyword
 Logging level.
 
 
+--
+
+*`log.flags`*::
++
+--
+This field contains the flags of the event.
+
+
 --
 
 *`event.created`*::

filebeat/reader/message.go

@@ -49,13 +49,28 @@ func (m *Message) IsEmpty() bool {
 	return false
 }
 
-func (msg *Message) AddFields(fields common.MapStr) {
+// AddFields adds fields to the message.
+func (m *Message) AddFields(fields common.MapStr) {
 	if fields == nil {
 		return
 	}
 
-	if msg.Fields == nil {
-		msg.Fields = common.MapStr{}
+	if m.Fields == nil {
+		m.Fields = common.MapStr{}
 	}
-	msg.Fields.Update(fields)
+	m.Fields.Update(fields)
+}
+
+// AddTagsWithKey adds tags to the message with an arbitrary key.
+// If the field does not exist, it is created.
+func (m *Message) AddFlagsWithKey(key string, flags ...string) error {
+	if len(flags) == 0 {
+		return nil
+	}
+
+	if m.Fields == nil {
+		m.Fields = common.MapStr{}
+	}
+
+	return common.AddTagsWithKey(m.Fields, key, flags)
 }

filebeat/reader/multiline/multiline.go

@@ -48,6 +48,7 @@ type Reader struct {
 	separator    []byte
 	last         []byte
 	numLines     int
+	truncated    int
 	err          error // last seen error
 	state        func(*Reader) (reader.Message, error)
 	message      reader.Message
@@ -262,13 +263,19 @@ func (mlr *Reader) clear() {
 	mlr.message = reader.Message{}
 	mlr.last = nil
 	mlr.numLines = 0
+	mlr.truncated = 0
 	mlr.err = nil
 }
 
 // finalize writes the existing content into the returned message and resets all reader variables.
 func (mlr *Reader) finalize() reader.Message {
+	if mlr.truncated > 0 {
+		mlr.message.AddFlagsWithKey("log.flags", "truncated")
+	}
+
 	// Copy message from existing content
 	msg := mlr.message
+
 	mlr.clear()
 	return msg
 }
@@ -303,6 +310,16 @@ func (mlr *Reader) addLine(m reader.Message) {
 		}
 		mlr.message.Content = append(tmp, m.Content[:space]...)
 		mlr.numLines++
+
+		// add number of truncated bytes to fields
+		diff := len(m.Content) - space
+		if diff > 0 {
+			mlr.truncated += diff
+		}
+	} else {
+		// increase the number of skipped bytes, if cannot add
+		mlr.truncated += len(m.Content)
+
 	}
 
 	mlr.last = m.Content

filebeat/reader/multiline/multiline_test.go

@@ -150,6 +150,41 @@ func TestMultilineBeforeNegateOKWithEmptyLine(t *testing.T) {
 	)
 }
 
+func TestMultilineAfterTruncated(t *testing.T) {
+	pattern := match.MustCompile(`^[ ]`) // next line is indented a space
+	maxLines := 2
+	testMultilineTruncated(t,
+		Config{
+			Pattern:  &pattern,
+			Match:    "after",
+			MaxLines: &maxLines,
+		},
+		2,
+		true,
+		[]string{
+			"line1\n line1.1\n line1.2\n",
+			"line2\n line2.1\n line2.2\n"},
+		[]string{
+			"line1\n line1.1",
+			"line2\n line2.1"},
+	)
+	testMultilineTruncated(t,
+		Config{
+			Pattern:  &pattern,
+			Match:    "after",
+			MaxLines: &maxLines,
+		},
+		2,
+		false,
+		[]string{
+			"line1\n line1.1\n",
+			"line2\n line2.1\n"},
+		[]string{
+			"line1\n line1.1",
+			"line2\n line2.1"},
+	)
+}
+
 func testMultilineOK(t *testing.T, cfg Config, events int, expected ...string) {
 	_, buf := createLineBuffer(expected...)
 	r := createMultilineTestReader(t, buf, cfg)
@@ -177,6 +212,54 @@ func testMultilineOK(t *testing.T, cfg Config, events int, expected ...string) {
 	}
 }
 
+func testMultilineTruncated(t *testing.T, cfg Config, events int, truncated bool, input, expected []string) {
+	_, buf := createLineBuffer(input...)
+	r := createMultilineTestReader(t, buf, cfg)
+
+	var messages []reader.Message
+	for {
+		message, err := r.Next()
+		if err != nil {
+			break
+		}
+
+		messages = append(messages, message)
+	}
+
+	if len(messages) != events {
+		t.Fatalf("expected %v lines, read only %v line(s)", len(expected), len(messages))
+	}
+
+	for _, message := range messages {
+		found := false
+		statusFlags, err := message.Fields.GetValue("log.flags")
+		if err != nil {
+			if !truncated {
+				assert.False(t, found)
+				return
+			}
+			t.Fatalf("error while getting log.status field: %v", err)
+		}
+
+		switch flags := statusFlags.(type) {
+		case []string:
+			for _, f := range flags {
+				if f == "truncated" {
+					found = true
+				}
+			}
+		default:
+			t.Fatalf("incorrect type for log.flags")
+		}
+
+		if truncated {
+			assert.True(t, found)
+		} else {
+			assert.False(t, found)
+		}
+	}
+}
+
 func createMultilineTestReader(t *testing.T, in *bytes.Buffer, cfg Config) reader.Reader {
 	encFactory, ok := encoding.FindEncoding("plain")
 	if !ok {

filebeat/reader/readfile/limit.go

@@ -38,6 +38,7 @@ func (r *LimitReader) Next() (reader.Message, error) {
 	message, err := r.reader.Next()
 	if len(message.Content) > r.maxBytes {
 		message.Content = message.Content[:r.maxBytes]
+		message.AddFlagsWithKey("log.flags", "truncated")
 	}
 	return message, err
 }

filebeat/reader/readfile/limit_test.go

@@ -0,0 +1,88 @@
+// 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.
+
+// +build !integration
+
+package readfile
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"github.com/elastic/beats/filebeat/reader"
+)
+
+type mockReader struct {
+	line []byte
+}
+
+func (m *mockReader) Next() (reader.Message, error) {
+	return reader.Message{
+		Content: m.line,
+	}, nil
+}
+
+var limitTests = []struct {
+	line      string
+	maxBytes  int
+	truncated bool
+}{
+	{"long-long-line", 5, true},
+	{"long-long-line", 3, true},
+	{"long-long-line", len("long-long-line"), false},
+}
+
+func TestLimitReader(t *testing.T) {
+	for _, test := range limitTests {
+		r := NewLimitReader(&mockReader{[]byte(test.line)}, test.maxBytes)
+
+		msg, err := r.Next()
+		if err != nil {
+			t.Fatalf("Error reading from mock reader: %v", err)
+		}
+
+		assert.Equal(t, test.maxBytes, len(msg.Content))
+
+		found := false
+		statusFlags, err := msg.Fields.GetValue("log.flags")
+		if err != nil {
+			if !test.truncated {
+				assert.False(t, found)
+				return
+			}
+			t.Fatalf("Error getting truncated value: %v", err)
+		}
+
+		switch flags := statusFlags.(type) {
+		case []string:
+			for _, f := range flags {
+				if f == "truncated" {
+					found = true
+				}
+			}
+		default:
+			t.Fatalf("incorrect type for log.flags")
+		}
+
+		if test.truncated {
+			assert.True(t, found)
+		} else {
+			assert.False(t, found)
+		}
+	}
+}

libbeat/common/mapstr.go

@@ -305,25 +305,38 @@ func MergeFields(ms, fields MapStr, underRoot bool) error {
 // exist then it will be created. If the tags field exists and is not a []string
 // then an error will be returned. It does not deduplicate the list of tags.
 func AddTags(ms MapStr, tags []string) error {
+	return AddTagsWithKey(ms, TagsKey, tags)
+}
+
+// AddTagsWithKey appends a tag to the key field of ms. If the field does not
+// exist then it will be created. If the field exists and is not a []string
+// then an error will be returned. It does not deduplicate the list.
+func AddTagsWithKey(ms MapStr, key string, tags []string) error {
 	if ms == nil || len(tags) == 0 {
 		return nil
 	}
-	eventTags, exists := ms[TagsKey]
-	if !exists {
-		ms[TagsKey] = tags
+
+	k, subMap, oldTags, present, err := mapFind(key, ms, true)
+	if err != nil {
+		return err
+	}
+
+	if !present {
+		subMap[k] = tags
 		return nil
 	}
 
-	switch arr := eventTags.(type) {
+	switch arr := oldTags.(type) {
 	case []string:
-		ms[TagsKey] = append(arr, tags...)
+		subMap[k] = append(arr, tags...)
 	case []interface{}:
 		for _, tag := range tags {
 			arr = append(arr, tag)
 		}
-		ms[TagsKey] = arr
+		subMap[k] = arr
 	default:
-		return errors.Errorf("expected string array by type is %T", eventTags)
+		return errors.Errorf("expected string array by type is %T", oldTags)
+
 	}
 	return nil
 }