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package logsource
import (
"context"
"errors"
"io"
"log/slog"
"github.com/nxadm/tail"
"gopkg.in/alecthomas/kingpin.v2"
"gopkg.in/tomb.v1"
)
var defaultConfig = tail.Config{
ReOpen: true, // reopen the file if it's rotated
MustExist: true, // fail immediately if the file is missing or has incorrect permissions
Follow: true, // run in follow mode
Poll: false, // poll for file changes instead of using inotify
Location: &tail.SeekInfo{Whence: io.SeekEnd}, // seek to end of file
Logger: tail.DiscardingLogger,
}
// A FileLogSource can read lines from a file.
type FileLogSource struct {
tailer *tail.Tail
unhealthy bool
LogSourceDefaults
}
// NewFileLogSource creates a new log source, tailing the given file.
func NewFileLogSource(path string, config tail.Config) (*FileLogSource, error) {
tailer, err := tail.TailFile(path, config)
if err != nil {
return nil, err
}
return &FileLogSource{tailer: tailer}, nil
}
func (s *FileLogSource) Close() error {
go func() {
// Stop() waits for the tailer goroutine to shut down, but it
// can be blocking on sending on the Lines channel...
for range s.tailer.Lines {
}
}()
// Do not call .CleanUp() if the file should be tailed again
// see also https://pkg.go.dev/github.com/nxadm/tail@v1.4.11#Tail.Cleanup
return s.tailer.Stop()
}
func (s *FileLogSource) Path() string {
return s.tailer.Filename
}
func (s *FileLogSource) Read(ctx context.Context) (string, error) {
select {
case line, ok := <-s.tailer.Lines:
if !ok {
s.unhealthy = true
if tailErr := s.tailer.Tomb.Err(); tailErr != nil && !errors.Is(tailErr, tomb.ErrStillAlive) {
return "", tailErr
}
return "", io.EOF
}
return line.Text, nil
case <-ctx.Done():
return "", ctx.Err()
}
}
// A fileLogSourceFactory is a factory that can create log sources
// from command line flags.
//
// Because this factory is enabled by default, it must always be
// registered last.
type fileLogSourceFactory struct {
LogSourceFactoryDefaults
path string
mustExist bool
debug bool
poll bool
source *FileLogSource
}
func (f *fileLogSourceFactory) Init(app *kingpin.Application) {
app.Flag("postfix.logfile_path", "Path where Postfix writes log entries.").Default("/var/log/mail.log").StringVar(&f.path)
app.Flag("postfix.logfile_must_exist", "Fail if the log file doesn't exist.").Default("true").BoolVar(&f.mustExist)
app.Flag("postfix.logfile_debug", "Enable debug logging for the log file.").Default("false").BoolVar(&f.debug)
app.Flag("postfix.logfile_poll", "Poll for file changes instead of using inotify.").Default("false").BoolVar(&f.poll)
}
// config returns a tail.Config configured from the factory's fields.
func (f fileLogSourceFactory) config() tail.Config {
conf := defaultConfig
conf.MustExist = f.mustExist
conf.Poll = f.poll
if f.debug {
conf.Logger = tail.DefaultLogger
}
return conf
}
func (f *fileLogSourceFactory) New(ctx context.Context) ([]LogSourceCloser, error) {
if f.path == "" {
return nil, nil
}
slog.Info("Reading log events from file", "path", f.path)
logSource, err := NewFileLogSource(f.path, f.config())
if err != nil {
return nil, err
}
f.source = logSource
return []LogSourceCloser{logSource}, nil
}
func (f *fileLogSourceFactory) Watchdog(ctx context.Context) bool {
if f.source == nil {
return false
}
return f.source.unhealthy
}
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