118 lines
2.4 KiB
Go
118 lines
2.4 KiB
Go
// Copyright (c) 2013 ActiveState Software Inc. All rights reserved.
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package watch
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import (
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"os"
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"runtime"
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"time"
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"github.com/hpcloud/tail/util"
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"gopkg.in/tomb.v1"
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)
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// PollingFileWatcher polls the file for changes.
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type PollingFileWatcher struct {
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Filename string
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Size int64
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}
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func NewPollingFileWatcher(filename string) *PollingFileWatcher {
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fw := &PollingFileWatcher{filename, 0}
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return fw
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}
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var POLL_DURATION time.Duration
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func (fw *PollingFileWatcher) BlockUntilExists(t *tomb.Tomb) error {
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for {
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if _, err := os.Stat(fw.Filename); err == nil {
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return nil
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} else if !os.IsNotExist(err) {
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return err
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}
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select {
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case <-time.After(POLL_DURATION):
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continue
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case <-t.Dying():
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return tomb.ErrDying
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}
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}
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panic("unreachable")
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}
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func (fw *PollingFileWatcher) ChangeEvents(t *tomb.Tomb, pos int64) (*FileChanges, error) {
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origFi, err := os.Stat(fw.Filename)
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if err != nil {
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return nil, err
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}
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changes := NewFileChanges()
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var prevModTime time.Time
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// XXX: use tomb.Tomb to cleanly manage these goroutines. replace
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// the fatal (below) with tomb's Kill.
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fw.Size = pos
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go func() {
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prevSize := fw.Size
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for {
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select {
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case <-t.Dying():
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return
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default:
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}
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time.Sleep(POLL_DURATION)
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fi, err := os.Stat(fw.Filename)
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if err != nil {
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// Windows cannot delete a file if a handle is still open (tail keeps one open)
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// so it gives access denied to anything trying to read it until all handles are released.
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if os.IsNotExist(err) || (runtime.GOOS == "windows" && os.IsPermission(err)) {
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// File does not exist (has been deleted).
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changes.NotifyDeleted()
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return
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}
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// XXX: report this error back to the user
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util.Fatal("Failed to stat file %v: %v", fw.Filename, err)
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}
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// File got moved/renamed?
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if !os.SameFile(origFi, fi) {
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changes.NotifyDeleted()
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return
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}
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// File got truncated?
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fw.Size = fi.Size()
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if prevSize > 0 && prevSize > fw.Size {
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changes.NotifyTruncated()
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prevSize = fw.Size
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continue
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}
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// File got bigger?
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if prevSize > 0 && prevSize < fw.Size {
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changes.NotifyModified()
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prevSize = fw.Size
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continue
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}
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prevSize = fw.Size
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// File was appended to (changed)?
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modTime := fi.ModTime()
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if modTime != prevModTime {
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prevModTime = modTime
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changes.NotifyModified()
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}
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}
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}()
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return changes, nil
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}
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func init() {
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POLL_DURATION = 250 * time.Millisecond
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}
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