[pkg/stanza] Fix issue where batching caused incorrect starting point (…

…open-telemetry#27773)

.chloggen/pkg-stanza-fileconsumer-reader-from-end-batches.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: bug_fix
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: filelogreceiver
+
+# A brief description of the change. Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Fix issue where batching of files could result in ignoring start_at setting.
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [27773]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: []

pkg/stanza/fileconsumer/file.go

@@ -118,6 +118,9 @@ func (m *Manager) poll(ctx context.Context) {
  matches = matches[m.maxBatchFiles:]
  }
  m.consume(ctx, matches)
+
+ // Any new files that appear should be consumed entirely
+ m.readerFactory.FromBeginning = true
 }
 
 func (m *Manager) consume(ctx context.Context, paths []string) {
@@ -145,9 +148,6 @@ func (m *Manager) consume(ctx context.Context, paths []string) {
  }
  wg.Wait()
 
- // Any new files that appear should be consumed entirely
- m.readerFactory.FromBeginning = true
-
  m.roller.roll(ctx, readers)
  m.saveCurrent(readers)
  m.syncLastPollFiles(ctx)

pkg/stanza/fileconsumer/file_test.go

@@ -1098,6 +1098,56 @@ func TestFileBatching(t *testing.T) {
  }
 }
 
+func TestFileBatchingRespectsStartAtEnd(t *testing.T) {
+ t.Parallel()
+
+ initFiles := 10
+ moreFiles := 10
+ maxConcurrentFiles := 2
+
+ tempDir := t.TempDir()
+ cfg := NewConfig().includeDir(tempDir)
+ cfg.StartAt = "end"
+ cfg.MaxConcurrentFiles = maxConcurrentFiles
+
+ operator, emitChan := buildTestManager(t, cfg)
+ operator.persister = testutil.NewMockPersister("test")
+
+ temps := make([]*os.File, 0, initFiles+moreFiles)
+ for i := 0; i < initFiles; i++ {
+ temps = append(temps, openTemp(t, tempDir))
+ }
+
+ // Write one log to each file
+ for i, temp := range temps {
+ message := fmt.Sprintf("file %d: %s", i, "written before start")
+ _, err := temp.WriteString(message + "\n")
+ require.NoError(t, err)
+ }
+
+ // Poll and expect no logs
+ operator.poll(context.Background())
+ expectNoTokens(t, emitChan)
+
+ // Create some more files
+ for i := 0; i < moreFiles; i++ {
+ temps = append(temps, openTemp(t, tempDir))
+ }
+
+ // Write a log to each file
+ expectedTokens := make([][]byte, 0, initFiles+moreFiles)
+ for i, temp := range temps {
+ message := fmt.Sprintf("file %d: %s", i, "written after start")
+ _, err := temp.WriteString(message + "\n")
+ require.NoError(t, err)
+ expectedTokens = append(expectedTokens, []byte(message))
+ }
+
+ // Poll again and expect one line from each file.
+ operator.poll(context.Background())
+ waitForTokens(t, emitChan, expectedTokens)
+}
+
 func TestFileReader_FingerprintUpdated(t *testing.T) {
  t.Parallel()