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[8.x](backport #40558) [Journald] Restart journalctl if it exits unexpectedly #40772

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Sep 13, 2024
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1 change: 1 addition & 0 deletions CHANGELOG.next.asciidoc
Original file line number Diff line number Diff line change
Expand Up @@ -114,6 +114,7 @@ https://github.com/elastic/beats/compare/v8.8.1\...main[Check the HEAD diff]
- Update Go version to 1.22.6. {pull}40528[40528]
- Aborts all active connections for Elasticsearch output. {pull}40572[40572]
- Closes beat Publisher on beat stop and by the Agent manager. {pull}40572[40572]
- The journald input now restarts if there is an error/crash {issue}32782[32782] {pull}40558[40558]

*Auditbeat*

Expand Down
13 changes: 10 additions & 3 deletions filebeat/input/journald/input.go
Original file line number Diff line number Diff line change
Expand Up @@ -132,6 +132,7 @@ func (inp *journald) Test(src cursor.Source, ctx input.TestContext) error {
"",
inp.Since,
src.Name(),
journalctl.Factory,
)
if err != nil {
return err
Expand Down Expand Up @@ -161,6 +162,7 @@ func (inp *journald) Run(
pos,
inp.Since,
src.Name(),
journalctl.Factory,
)
if err != nil {
return fmt.Errorf("could not start journal reader: %w", err)
Expand All @@ -179,12 +181,17 @@ func (inp *journald) Run(
for {
entry, err := parser.Next()
if err != nil {
switch {
// The input has been cancelled, gracefully return
if errors.Is(err, journalctl.ErrCancelled) {
case errors.Is(err, journalctl.ErrCancelled):
return nil
// Journalctl is restarting, do ignore the empty event
case errors.Is(err, journalctl.ErrRestarting):
continue
default:
logger.Errorf("could not read event: %s", err)
return err
}
logger.Errorf("could not read event: %s", err)
return err
}

event := entry.ToEvent()
Expand Down
130 changes: 130 additions & 0 deletions filebeat/input/journald/pkg/journalctl/jctlmock_test.go

Some generated files are not rendered by default. Learn more about how customized files appear on GitHub.

147 changes: 147 additions & 0 deletions filebeat/input/journald/pkg/journalctl/journalctl.go
Original file line number Diff line number Diff line change
@@ -0,0 +1,147 @@
// 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.

package journalctl

import (
"bufio"
"errors"
"fmt"
"io"
"os/exec"
"strings"

input "github.com/elastic/beats/v7/filebeat/input/v2"
"github.com/elastic/elastic-agent-libs/logp"
)

type journalctl struct {
cmd *exec.Cmd
dataChan chan []byte
stdout io.ReadCloser
stderr io.ReadCloser

logger *logp.Logger
canceler input.Canceler
}

// Factory returns an instance of journalctl ready to use.
// The caller is responsible for calling Kill to ensure the
// journalctl process created is correctly terminated.
//
// The returned type is an interface to allow mocking for testing
func Factory(canceller input.Canceler, logger *logp.Logger, binary string, args ...string) (Jctl, error) {
cmd := exec.Command(binary, args...)

jctl := journalctl{
canceler: canceller,
cmd: cmd,
dataChan: make(chan []byte),
logger: logger,
}

var err error
jctl.stdout, err = cmd.StdoutPipe()
if err != nil {
return &journalctl{}, fmt.Errorf("cannot get stdout pipe: %w", err)
}
jctl.stderr, err = cmd.StderrPipe()
if err != nil {
return &journalctl{}, fmt.Errorf("cannot get stderr pipe: %w", err)
}

// This gorroutune reads the stderr from the journalctl process, if the
// process exits for any reason, then its stderr is closed, this goroutine
// gets an EOF error and exits
go func() {
defer jctl.logger.Debug("stderr reader goroutine done")
reader := bufio.NewReader(jctl.stderr)
for {
line, err := reader.ReadString('\n')
if err != nil {
if !errors.Is(err, io.EOF) {
logger.Errorf("cannot read from journalctl stderr: %s", err)
}
return
}

logger.Errorf("Journalctl wrote to stderr: %s", line)
}
}()

// This goroutine reads the stdout from the journalctl process and makes
// the data available via the `Next()` method.
// If the journalctl process exits for any reason, then its stdout is closed
// this goroutine gets an EOF error and exits.
go func() {
defer jctl.logger.Debug("stdout reader goroutine done")
defer close(jctl.dataChan)
reader := bufio.NewReader(jctl.stdout)
for {
data, err := reader.ReadBytes('\n')
if err != nil {
if !errors.Is(err, io.EOF) {
logger.Errorf("cannot read from journalctl stdout: %s", err)
}
return
}

select {
case <-jctl.canceler.Done():
return
case jctl.dataChan <- data:
}
}
}()

logger.Infof("Journalctl command: journalctl %s", strings.Join(args, " "))

if err := cmd.Start(); err != nil {
return &journalctl{}, fmt.Errorf("cannot start journalctl: %w", err)
}

logger.Infof("journalctl started with PID %d", cmd.Process.Pid)

// Whenever the journalctl process exits, the `Wait` call returns,
// if there was an error it is logged and this goroutine exits.
go func() {
if err := cmd.Wait(); err != nil {
jctl.logger.Errorf("journalctl exited with an error, exit code %d ", cmd.ProcessState.ExitCode())
}
}()

return &jctl, nil
}

// Kill Terminates the journalctl process using a SIGKILL.
func (j *journalctl) Kill() error {
j.logger.Debug("sending SIGKILL to journalctl")
err := j.cmd.Process.Kill()
return err
}

func (j *journalctl) Next(cancel input.Canceler) ([]byte, error) {
select {
case <-cancel.Done():
return []byte{}, ErrCancelled
case d, open := <-j.dataChan:
if !open {
return []byte{}, errors.New("no more data to read, journalctl might have exited unexpectedly")
}
return d, nil
}
}
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