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Merge pull request #6 from srid/bug99139_copytruncate 

copytruncate support,

truncation detection for both inotify and polling file watchers along with test cases, plus a fix for issue #5.
This commit is contained in:
Sridhar Ratnakumar 2013-05-28 14:03:12 -07:00
parent ad34bda357 976fc15b81
commit b664e9fc9d
4 changed files with 139 additions and 29 deletions
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2
CHANGES.md
View File

@ -1,6 +1,8 @@
# May, 2013
* Recognize deletions/renames when using polling file watcher (PR #1)
* Detect file truncation
* Fix potential race condition when reopening the file (issue 5)
# Feb, 2013

7
tail.go
View File

@ -102,8 +102,7 @@ func (tail *Tail) reopen() error {
if err != nil {
if os.IsNotExist(err) {
log.Printf("Waiting for %s to appear...", tail.Filename)
err := tail.watcher.BlockUntilExists()
if err != nil {
if err := tail.watcher.BlockUntilExists(); err != nil {
return fmt.Errorf("Failed to detect creation of %s: %s", tail.Filename, err)
}
continue
@ -187,10 +186,10 @@ func (tail *Tail) tailFileSync() {
if !ok {
changes = nil // XXX: how to kill changes' goroutine?
// File got deleted/renamed
// File got deleted/renamed/truncated.
if tail.ReOpen {
// TODO: no logging in a library?
log.Printf("Re-opening moved/deleted file %s ...", tail.Filename)
log.Printf("Re-opening moved/deleted/truncated file %s ...", tail.Filename)
err := tail.reopen()
if err != nil {
tail.close()

79
tail_test.go
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@ -14,6 +14,7 @@ import (
)
func init() {
// Clear the temporary test directory
err := os.RemoveAll(".test")
if err != nil {
panic(err)
@ -122,18 +123,71 @@ func _TestReOpen(_t *testing.T, poll bool) {
<-time.After(100 * time.Millisecond)
t.RemoveFile("test.txt")
println("Stopping (REOPEN)...")
tail.Stop()
}
// The use of polling file watcher could affect file rotation
// (detected via renames), so test these explicitly.
func TestReOpenWithPoll(_t *testing.T) {
func TestReOpenInotify(_t *testing.T) {
_TestReOpen(_t, false)
}
func TestReOpenPolling(_t *testing.T) {
_TestReOpen(_t, true)
}
func TestReOpenWithoutPoll(_t *testing.T) {
_TestReOpen(_t, false)
func _TestReSeek(_t *testing.T, poll bool) {
var name string
if poll {
name = "reseek-polling"
} else {
name = "reseek-inotify"
}
t := NewTailTest(name, _t)
t.CreateFile("test.txt", "a really long string goes here\nhello\nworld\n")
tail := t.StartTail(
"test.txt",
Config{Follow: true, ReOpen: true, Poll: poll, Location: -1})
go t.VerifyTailOutput(tail, []string{
"a really long string goes here", "hello", "world", "h311o", "w0r1d", "endofworld"})
// truncate now
<-time.After(100 * time.Millisecond)
if poll {
// Give polling a chance to read the just-written lines (more;
// data), before we truncate the file again below.
<-time.After(POLL_DURATION)
}
println("truncating..")
t.TruncateFile("test.txt", "h311o\nw0r1d\nendofworld\n")
// XXX: is this required for this test function?
if poll {
// Give polling a chance to read the just-written lines (more;
// data), before we recreate the file again below.
<-time.After(POLL_DURATION)
}
// Delete after a reasonable delay, to give tail sufficient time
// to read all lines.
<-time.After(100 * time.Millisecond)
t.RemoveFile("test.txt")
println("Stopping (RESEEK)...")
tail.Stop()
}
// The use of polling file watcher could affect file rotation
// (detected via renames), so test these explicitly.
func TestReSeekInotify(_t *testing.T) {
_TestReSeek(_t, false)
}
func TestReSeekPolling(_t *testing.T) {
_TestReSeek(_t, true)
}
// Test library
@ -150,6 +204,10 @@ func NewTailTest(name string, t *testing.T) TailTest {
if err != nil {
tt.Fatal(err)
}
// Use a smaller poll duration for faster test runs.
POLL_DURATION = 25 * time.Millisecond
return tt
}
@ -188,6 +246,18 @@ func (t TailTest) AppendFile(name string, contents string) {
}
}
func (t TailTest) TruncateFile(name string, contents string) {
f, err := os.OpenFile(t.path+"/"+name, os.O_TRUNC|os.O_WRONLY, 0600)
if err != nil {
t.Fatal(err)
}
defer f.Close()
_, err = f.WriteString(contents)
if err != nil {
t.Fatal(err)
}
}
func (t TailTest) StartTail(name string, config Config) *Tail {
tail, err := TailFile(t.path+"/"+name, config)
if err != nil {
@ -211,7 +281,8 @@ func (t TailTest) VerifyTailOutput(tail *Tail, lines []string) {
t.Fatalf("tail.Lines returned nil; not possible")
}
if tailedLine.Text != line {
t.Fatalf("mismatch; %s != %s", tailedLine.Text, line)
t.Fatalf("mismatch; %s (actual) != %s (expected)",
tailedLine.Text, line)
}
}
line, ok := <-tail.Lines

60
watch.go
View File

@ -6,14 +6,14 @@ import (
"github.com/howeyc/fsnotify"
"os"
"path/filepath"
"time"
"sync"
"time"
)
// FileWatcher monitors file-level events.
type FileWatcher interface {
// BlockUntilExists blocks until the missing file comes into
// existence. If the file already exists, block until it is recreated.
// existence. If the file already exists, returns immediately.
BlockUntilExists() error
// ChangeEvents returns a channel of events corresponding to the
@ -24,10 +24,11 @@ type FileWatcher interface {
// InotifyFileWatcher uses inotify to monitor file changes.
type InotifyFileWatcher struct {
Filename string
Size int64
}
func NewInotifyFileWatcher(filename string) *InotifyFileWatcher {
fw := &InotifyFileWatcher{filename}
fw := &InotifyFileWatcher{filename, 0}
return fw
}
@ -37,11 +38,23 @@ func (fw *InotifyFileWatcher) BlockUntilExists() error {
return err
}
defer w.Close()
err = w.WatchFlags(filepath.Dir(fw.Filename), fsnotify.FSN_CREATE)
dirname := filepath.Dir(fw.Filename)
// Watch for new files to be created in the parent directory.
err = w.WatchFlags(dirname, fsnotify.FSN_CREATE)
if err != nil {
return err
}
defer w.RemoveWatch(filepath.Dir(fw.Filename))
// Do a real check now as the file might have been created before
// calling `WatchFlags` above.
if _, err = os.Stat(fw.Filename); !os.IsNotExist(err) {
// file exists, or stat returned an error.
return err
}
for {
evt := <-w.Event
if evt.Name == fw.Filename {
@ -52,7 +65,7 @@ func (fw *InotifyFileWatcher) BlockUntilExists() error {
}
// ChangeEvents returns a channel that gets updated when the file is ready to be read.
func (fw *InotifyFileWatcher) ChangeEvents(_ os.FileInfo) chan bool {
func (fw *InotifyFileWatcher) ChangeEvents(fi os.FileInfo) chan bool {
w, err := fsnotify.NewWatcher()
if err != nil {
panic(err)
@ -64,20 +77,36 @@ func (fw *InotifyFileWatcher) ChangeEvents(_ os.FileInfo) chan bool {
ch := make(chan bool)
fw.Size = fi.Size()
go func() {
defer w.Close()
defer w.RemoveWatch(fw.Filename)
defer close(ch)
for {
prevSize := fw.Size
evt := <-w.Event
switch {
case evt.IsDelete():
fallthrough
case evt.IsRename():
close(ch)
w.RemoveWatch(fw.Filename)
w.Close()
return
case evt.IsModify():
fi, err := os.Stat(fw.Filename)
if err != nil {
// XXX: no panic here
panic(err)
}
fw.Size = fi.Size()
if prevSize > 0 && prevSize > fw.Size {
return
}
// send only if channel is empty.
select {
case ch <- true:
@ -93,17 +122,16 @@ func (fw *InotifyFileWatcher) ChangeEvents(_ os.FileInfo) chan bool {
// PollingFileWatcher polls the file for changes.
type PollingFileWatcher struct {
Filename string
Size int64
}
func NewPollingFileWatcher(filename string) *PollingFileWatcher {
fw := &PollingFileWatcher{filename}
fw := &PollingFileWatcher{filename, 0}
return fw
}
var POLL_DURATION time.Duration
// BlockUntilExists blocks until the file comes into existence. If the
// file already exists, then block until it is created again.
func (fw *PollingFileWatcher) BlockUntilExists() error {
for {
if _, err := os.Stat(fw.Filename); err == nil {
@ -132,7 +160,10 @@ func (fw *PollingFileWatcher) ChangeEvents(origFi os.FileInfo) chan bool {
}()
}
fw.Size = origFi.Size()
go func() {
prevSize := fw.Size
for {
select {
case <-stop:
@ -157,6 +188,13 @@ func (fw *PollingFileWatcher) ChangeEvents(origFi os.FileInfo) chan bool {
continue
}
// Was the file truncated?
fw.Size = fi.Size()
if prevSize > 0 && prevSize > fw.Size {
once.Do(stopAndClose)
continue
}
// If the file was changed since last check, notify.
modTime := fi.ModTime()
if modTime != prevModTime {