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fixes to extra-record file watcher (#2298)

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* Fix excess error message during writes

Fixes #2290

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>

* retry filewatcher on removed files

This should handled if files are deleted and added again, and for rename
scenarios.

Fixes #2289

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>

* test more write and remove in filewatcher

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>

---------

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>
This commit is contained in:
Kristoffer Dalby 2024-12-16 11:26:56 +01:00 • committed by GitHub
parent 5345f19693
commit ccc895b4c6
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GPG key ID: B5690EEEBB952194
2 changed files with 119 additions and 10 deletions
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47
hscontrol/dns/extrarecords.go
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@ -7,6 +7,7 @@ import (
"os"
"sync"
"github.com/cenkalti/backoff/v4"
"github.com/fsnotify/fsnotify"
"github.com/rs/zerolog/log"
"tailscale.com/tailcfg"
@ -83,12 +84,39 @@ func (e *ExtraRecordsMan) Run() {
log.Error().Caller().Msgf("file watcher event channel closing")
return
}
switch event.Op {
case fsnotify.Create, fsnotify.Write, fsnotify.Chmod:
log.Trace().Caller().Str("path", event.Name).Str("op", event.Op.String()).Msg("extra records received filewatch event")
if event.Name != e.path {
continue
}
e.updateRecords()
log.Trace().Caller().Str("path", event.Name).Str("op", event.Op.String()).Msg("extra records received filewatch event")
if event.Name != e.path {
continue
// If a file is removed or renamed, fsnotify will loose track of it
// and not watch it. We will therefore attempt to re-add it with a backoff.
case fsnotify.Remove, fsnotify.Rename:
err := backoff.Retry(func() error {
if _, err := os.Stat(e.path); err != nil {
return err
}
return nil
}, backoff.NewExponentialBackOff())
if err != nil {
log.Error().Caller().Err(err).Msgf("extra records filewatcher retrying to find file after delete")
continue
}
err = e.watcher.Add(e.path)
if err != nil {
log.Error().Caller().Err(err).Msgf("extra records filewatcher re-adding file after delete failed, giving up.")
return
} else {
log.Trace().Caller().Str("path", e.path).Msg("extra records file re-added after delete")
e.updateRecords()
}
}
e.updateRecords()
case err, ok := <-e.watcher.Errors:
if !ok {
@ -116,6 +144,11 @@ func (e *ExtraRecordsMan) updateRecords() {
return
}
// If there are no records, ignore the update.
if records == nil {
return
}
e.mu.Lock()
defer e.mu.Unlock()
@ -143,6 +176,12 @@ func readExtraRecordsFromPath(path string) ([]tailcfg.DNSRecord, [32]byte, error
return nil, [32]byte{}, fmt.Errorf("reading path: %s, err: %w", path, err)
}
// If the read was triggered too fast, and the file is not complete, ignore the update
// if the file is empty. A consecutive update will be triggered when the file is complete.
if len(b) == 0 {
return nil, [32]byte{}, nil
}
var records []tailcfg.DNSRecord
err = json.Unmarshal(b, &records)
if err != nil {