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fswatcher.go
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fswatcher.go
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// Copyright 2018-2019 The grok_exporter Authors
//
// Licensed 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 fswatcher
import (
"fmt"
"github.com/jdrews/go-tailer/glob"
"github.com/sirupsen/logrus"
"io"
"os"
"path/filepath"
"time"
)
type FileTailer interface {
Lines() chan *Line
Errors() chan Error
Close()
}
type Line struct {
Line string
File string
Extra interface{}
}
// ideas how this might look like in the config file:
//
// * input section may specify multiple inputs and use globs
//
// * metrics may define filters to specify which files they apply to:
// - filename_filter: filter file names, like *server1*
// - filepath_filter: filter path, like /logs/server1/*
// Heads up: filters use globs while matches use regular expressions.
// Moreover, we should provide vars {{.filename}} and {{.filepath}} for labels.
type fileTailer struct {
globs []glob.Glob
watchedDirs []*Dir
watchedFiles map[string]*fileWithReader // path -> fileWithReader
osSpecific fswatcher
lines chan *Line
errors chan Error
done chan struct{}
}
type fswatcher interface {
io.Closer
runFseventProducerLoop() fseventProducerLoop
processEvent(t *fileTailer, event fsevent, log logrus.FieldLogger) Error
watchDir(path string) (*Dir, Error)
unwatchDir(dir *Dir) error
watchFile(file fileMeta) Error
}
type fseventProducerLoop interface {
Close()
Events() chan fsevent
Errors() chan Error
}
type fsevent interface{}
type fileMeta interface {
Fd() uintptr
Name() string
}
func (t *fileTailer) Lines() chan *Line {
return t.lines
}
func (t *fileTailer) Errors() chan Error {
return t.errors
}
// Close() triggers the shutdown of the file tailer.
// The file tailer will eventually terminate,
// but after Close() returns it might still be running in the background for a few milliseconds.
func (t *fileTailer) Close() {
// Closing the done channel will stop the consumer loop.
// Deferred functions within the consumer loop will close the producer loop.
close(t.done)
}
func RunFileTailer(globs []glob.Glob, readall bool, failOnMissingFile bool, log logrus.FieldLogger) (FileTailer, error) {
return runFileTailer(initWatcher, globs, readall, failOnMissingFile, log)
}
func RunPollingFileTailer(globs []glob.Glob, readall bool, failOnMissingFile bool, pollInterval time.Duration, log logrus.FieldLogger) (FileTailer, error) {
initFunc := func() (fswatcher, Error) {
return initPollingWatcher(pollInterval)
}
return runFileTailer(initFunc, globs, readall, failOnMissingFile, log)
}
func runFileTailer(initFunc func() (fswatcher, Error), globs []glob.Glob, readall bool, failOnMissingFile bool, log logrus.FieldLogger) (FileTailer, error) {
var (
t *fileTailer
Err Error
)
t = &fileTailer{
globs: globs,
watchedFiles: make(map[string]*fileWithReader),
lines: make(chan *Line),
errors: make(chan Error),
done: make(chan struct{}),
}
t.osSpecific, Err = initFunc()
if Err != nil {
return nil, Err
}
go func() {
defer t.shutdown()
Err = t.watchDirs(log)
if Err != nil {
select {
case <-t.done:
case t.errors <- Err:
}
return
}
eventProducerLoop := t.osSpecific.runFseventProducerLoop()
defer eventProducerLoop.Close()
for _, dir := range t.watchedDirs {
dirLogger := log.WithField("directory", dir.Path())
dirLogger.Debugf("initializing directory")
Err = t.syncFilesInDir(dir, readall, dirLogger) // This may already write lines to the lines channel, so we will not go past this line unless the consumer starts reading lines.
if Err != nil {
select {
case <-t.done:
case t.errors <- Err:
}
return
}
}
// make sure at least one logfile was found for each glob
if failOnMissingFile {
missingFileError := t.checkMissingFile()
if missingFileError != nil {
select {
case <-t.done:
case t.errors <- missingFileError:
}
return
}
}
for { // event consumer loop
select {
case <-t.done:
return
case event, open := <-eventProducerLoop.Events():
if !open {
return
}
processEventError := t.osSpecific.processEvent(t, event, log)
if processEventError != nil {
select {
case <-t.done:
case t.errors <- processEventError:
}
return
}
case err, open := <-eventProducerLoop.Errors():
if !open {
return
}
select {
case <-t.done:
case t.errors <- NewError(NotSpecified, err, "error reading file system events"):
}
return
}
}
}()
return t, nil
}
func (t *fileTailer) shutdown() {
close(t.lines)
close(t.errors)
logger := logrus.New()
warnf := func(format string, args ...interface{}) {
logger.Warnf("error while shutting down the file system watcher: %v", fmt.Sprintf(format, args))
}
for _, dir := range t.watchedDirs {
err := t.osSpecific.unwatchDir(dir)
if err != nil {
warnf("%v", err)
}
}
err := t.osSpecific.Close()
if err != nil {
warnf("%v", err)
}
for _, file := range t.watchedFiles {
err = file.file.Close()
if err != nil {
warnf("close(%q) failed: %v", file.file.Name(), err)
}
}
}
func (t *fileTailer) watchDirs(log logrus.FieldLogger) Error {
var (
Err Error
dirPaths []string
dirPath string
)
dirPaths, Err = uniqueDirs(t.globs)
if Err != nil {
return Err
}
for _, dirPath = range dirPaths {
log.Debugf("watching directory %v", dirPath)
dir, Err := t.osSpecific.watchDir(dirPath)
if Err != nil {
return Err
}
t.watchedDirs = append(t.watchedDirs, dir)
}
return nil
}
func (t *fileTailer) syncFilesInDir(dir *Dir, readall bool, log logrus.FieldLogger) Error {
watchedFilesAfter := make(map[string]*fileWithReader)
for path, file := range t.watchedFiles {
if filepath.Dir(path) != dir.Path() {
watchedFilesAfter[path] = file
}
}
fileInfos, Err := dir.ls()
if Err != nil {
return Err
}
for _, fileInfo := range fileInfos {
filePath := filepath.Join(dir.Path(), fileInfo.Name())
fileLogger := log.WithField("file", fileInfo.Name())
if !anyGlobMatches(t.globs, filePath) {
fileLogger.Debug("skipping file, because file name does not match")
continue
}
if fileInfo.IsDir() {
fileLogger.Debug("skipping, because it is a directory")
continue
}
alreadyWatched, Err := findSameFile(t, fileInfo, filePath)
if Err != nil {
return Err
}
if alreadyWatched != nil {
if alreadyWatched.file.Name() != filePath { // file is already watched but renamed
renamedFile, err := NewFile(alreadyWatched.file, filePath)
if err != nil {
return NewErrorf(NotSpecified, err, "%v: failed to follow moved file", filePath)
}
fileLogger.WithField("fd", renamedFile.Fd()).Infof("file with old_fd=%v was moved from old_path=%v", alreadyWatched.file.Fd(), alreadyWatched.file.Name())
alreadyWatched.file.Close()
Err = t.osSpecific.watchFile(renamedFile)
if Err != nil {
renamedFile.Close()
return Err
}
alreadyWatched.file = renamedFile // re-use lineReader
Err = t.readNewLines(alreadyWatched, fileLogger)
if Err != nil {
alreadyWatched.file.Close()
return Err
}
watchedFilesAfter[filePath] = alreadyWatched
} else {
fileLogger.Debug("skipping, because file is already watched")
watchedFilesAfter[filePath] = alreadyWatched
}
continue
}
newFile, Err := open(filePath)
if Err != nil {
if Err.Type() == FileNotFound {
fileLogger.Debug("skipping, because file does no longer exist")
continue
} else {
return Err
}
}
if !readall {
_, err := newFile.Seek(0, io.SeekEnd)
if err != nil {
newFile.Close()
return NewError(NotSpecified, os.NewSyscallError("seek", err), filePath)
}
}
fileLogger = fileLogger.WithField("fd", newFile.Fd())
fileLogger.Info("watching new file")
Err = t.osSpecific.watchFile(newFile)
if Err != nil {
newFile.Close()
return Err
}
newFileWithReader := &fileWithReader{file: newFile, reader: NewLineReader()}
Err = t.readNewLines(newFileWithReader, fileLogger)
if Err != nil {
newFile.Close()
return Err
}
watchedFilesAfter[filePath] = newFileWithReader
}
for _, f := range t.watchedFiles {
if !contains(watchedFilesAfter, f) {
fileLogger := log.WithField("file", filepath.Base(f.file.Name())).WithField("fd", f.file.Fd())
fileLogger.Info("file was removed, closing and un-watching")
f.file.Close()
}
}
t.watchedFiles = watchedFilesAfter
return nil
}
func (t *fileTailer) readNewLines(file *fileWithReader, log logrus.FieldLogger) Error {
var (
line string
eof bool
err error
)
for {
line, eof, err = file.reader.ReadLine(file.file)
if err != nil {
return NewErrorf(NotSpecified, err, "%v: read() failed", file.file.Name())
}
if eof {
return nil
}
log.Debugf("read line %q", line)
select {
case <-t.done:
return nil
case t.lines <- &Line{Line: line, File: file.file.Name()}:
}
}
}
func (t *fileTailer) checkMissingFile() Error {
OUTER:
for _, g := range t.globs {
for watchedFileName := range t.watchedFiles {
if g.Match(watchedFileName) {
continue OUTER
}
}
// Error message must be phrased so that it makes sense for globs,
// but also if g is a plain path without wildcards.
return NewErrorf(FileNotFound, nil, "%v: no such file", g)
}
return nil
}
// Gets the directory paths from the glob expressions,
// and makes sure these directories exist.
func uniqueDirs(globs []glob.Glob) ([]string, Error) {
var (
result = make([]string, 0, len(globs))
g glob.Glob
dirInfo os.FileInfo
err error
)
for _, g = range globs {
if containsString(result, g.Dir()) {
continue
}
dirInfo, err = os.Stat(g.Dir())
if err != nil {
if os.IsNotExist(err) {
return nil, NewErrorf(DirectoryNotFound, nil, "%q: no such directory", g.Dir())
}
return nil, NewErrorf(NotSpecified, err, "%q: stat() failed", g.Dir())
}
if !dirInfo.IsDir() {
return nil, NewErrorf(NotSpecified, nil, "%q is not a directory", g.Dir())
}
result = append(result, g.Dir())
}
return result, nil
}
func anyGlobMatches(globs []glob.Glob, path string) bool {
for _, pattern := range globs {
if pattern.Match(path) {
return true
}
}
return false
}
func containsString(list []string, s string) bool {
for _, existing := range list {
if existing == s {
return true
}
}
return false
}
func contains(list map[string]*fileWithReader, f *fileWithReader) bool {
for _, existing := range list {
if existing == f {
return true
}
}
return false
}