Properly handle inotify's IN_Q_OVERFLOW event (#149)
* Properly handle inotify's IN_Q_OVERFLOW event
Upon receiving an event with IN_Q_OVERFLOW set in the mask, generate an
error on the Errors chan, so that the application can take appropriate
action.
* Use a well-defined error (ErrEventOverflow) for inotify overflow
* Add a test for inotify queue overflow
diff --git a/fsnotify.go b/fsnotify.go
index e7f55fe..190bf0d 100644
--- a/fsnotify.go
+++ b/fsnotify.go
@@ -9,6 +9,7 @@
import (
"bytes"
+ "errors"
"fmt"
)
@@ -60,3 +61,6 @@
func (e Event) String() string {
return fmt.Sprintf("%q: %s", e.Name, e.Op.String())
}
+
+// Common errors that can be reported by a watcher
+var ErrEventOverflow = errors.New("fsnotify queue overflow")
diff --git a/inotify.go b/inotify.go
index f3b74c5..bfa9dbc 100644
--- a/inotify.go
+++ b/inotify.go
@@ -245,6 +245,15 @@
mask := uint32(raw.Mask)
nameLen := uint32(raw.Len)
+
+ if mask&unix.IN_Q_OVERFLOW != 0 {
+ select {
+ case w.Errors <- ErrEventOverflow:
+ case <-w.done:
+ return
+ }
+ }
+
// If the event happened to the watched directory or the watched file, the kernel
// doesn't append the filename to the event, but we would like to always fill the
// the "Name" field with a valid filename. We retrieve the path of the watch from
diff --git a/inotify_test.go b/inotify_test.go
index a4bb202..6771a1c 100644
--- a/inotify_test.go
+++ b/inotify_test.go
@@ -358,3 +358,94 @@
t.Fatalf("Expected paths len is 0, but got: %d, %v", len(w.paths), w.paths)
}
}
+
+func TestInotifyOverflow(t *testing.T) {
+ // We need to generate many more events than the
+ // fs.inotify.max_queued_events sysctl setting.
+ // We use multiple goroutines (one per directory)
+ // to speed up file creation.
+ numDirs := 128
+ numFiles := 1024
+
+ testDir := tempMkdir(t)
+ defer os.RemoveAll(testDir)
+
+ w, err := NewWatcher()
+ if err != nil {
+ t.Fatalf("Failed to create watcher: %v", err)
+ }
+ defer w.Close()
+
+ for dn := 0; dn < numDirs; dn++ {
+ testSubdir := fmt.Sprintf("%s/%d", testDir, dn)
+
+ err := os.Mkdir(testSubdir, 0777)
+ if err != nil {
+ t.Fatalf("Cannot create subdir: %v", err)
+ }
+
+ err = w.Add(testSubdir)
+ if err != nil {
+ t.Fatalf("Failed to add subdir: %v", err)
+ }
+ }
+
+ errChan := make(chan error, numDirs*numFiles)
+
+ for dn := 0; dn < numDirs; dn++ {
+ testSubdir := fmt.Sprintf("%s/%d", testDir, dn)
+
+ go func() {
+ for fn := 0; fn < numFiles; fn++ {
+ testFile := fmt.Sprintf("%s/%d", testSubdir, fn)
+
+ handle, err := os.Create(testFile)
+ if err != nil {
+ errChan <- fmt.Errorf("Create failed: %v", err)
+ continue
+ }
+
+ err = handle.Close()
+ if err != nil {
+ errChan <- fmt.Errorf("Close failed: %v", err)
+ continue
+ }
+ }
+ }()
+ }
+
+ creates := 0
+ overflows := 0
+
+ after := time.After(10 * time.Second)
+ for overflows == 0 && creates < numDirs*numFiles {
+ select {
+ case <-after:
+ t.Fatalf("Not done")
+ case err := <-errChan:
+ t.Fatalf("Got an error from file creator goroutine: %v", err)
+ case err := <-w.Errors:
+ if err == ErrEventOverflow {
+ overflows++
+ } else {
+ t.Fatalf("Got an error from watcher: %v", err)
+ }
+ case evt := <-w.Events:
+ if !strings.HasPrefix(evt.Name, testDir) {
+ t.Fatalf("Got an event for an unknown file: %s", evt.Name)
+ }
+ if evt.Op == Create {
+ creates++
+ }
+ }
+ }
+
+ if creates == numDirs*numFiles {
+ t.Fatalf("Could not trigger overflow")
+ }
+
+ if overflows == 0 {
+ t.Fatalf("No overflow and not enough creates (expected %d, got %d)",
+ numDirs*numFiles, creates)
+ }
+}
