[pkg/stanza] Stop readerFactory from returning an error when creating…

… an unsafeReader (open-telemetry#12767)

Because the unsafeReader is not linked to any file, it caused an error when the readerBuilder tried to set its offset to the end of the file. Because the unsafeReader is later initialized with other data, we can simply ignore setting the offset here, because it will be overwritten anyway.

pkg/stanza/fileconsumer/reader_factory.go

@@ -47,7 +47,7 @@ func (f *readerFactory) copy(old *Reader, newFile *os.File) (*Reader, error) {
 }
 
 func (f *readerFactory) unsafeReader() (*Reader, error) {
- return f.newReaderBuilder().build()
+ return f.newReaderBuilder().Unsafe().build()
 }
 
 func (f *readerFactory) newFingerprint(file *os.File) (*Fingerprint, error) {
@@ -60,6 +60,7 @@ type readerBuilder struct {
  fp *Fingerprint
  offset int64
  splitter *helper.Splitter
+ isUnsafe bool
 }
 
 func (f *readerFactory) newReaderBuilder() *readerBuilder {
@@ -86,6 +87,11 @@ func (b *readerBuilder) withOffset(offset int64) *readerBuilder {
  return b
 }
 
+func (b *readerBuilder) Unsafe() *readerBuilder {
+ b.isUnsafe = true
+ return b
+}
+
 func (b *readerBuilder) build() (r *Reader, err error) {
  r = &Reader{
  readerConfig: b.readerConfig,
@@ -122,7 +128,8 @@ func (b *readerBuilder) build() (r *Reader, err error) {
  r.Fingerprint = fp
  }
 
- if !b.fromBeginning {
+ // unsafeReader has the file set to nil, so don't try emending its offset.
+ if !b.fromBeginning && !b.isUnsafe {
  if err := r.offsetToEnd(); err != nil {
  return nil, err
  }

unreleased/pkgstanza-remove-overwritting-offset-in-file-reader.yaml

@@ -0,0 +1,9 @@
+change_type: bug_fix
+
+component: pkg/stanza
+
+note: Stop readerFactory from returning an error when creating an unsafeReader
+
+issues: [12766]
+
+subtext: This bug caused the filelog receiver to crash when the collector was restarted and the logs were being read from the end of the file