fix hang with podman events file logger

podman --events-backend file events --stream=false should never hang. The
problem is that our tail library will wait for the file to be created
which makes sense when we do not run with --stream=false. To fix this we
can just always create the file when the logger is initialized. This
would also help to report errors early on in case the file is not
accessible.

Fixes part one from #15688

Signed-off-by: Paul Holzinger <pholzing@redhat.com>

libpod/events/events_linux.go

@@ -18,7 +18,7 @@ func NewEventer(options EventerOptions) (Eventer, error) {
 		}
 		return eventer, nil
 	case strings.ToUpper(LogFile.String()):
-		return EventLogFile{options}, nil
+		return newLogFileEventer(options)
 	case strings.ToUpper(Null.String()):
 		return NewNullEventer(), nil
 	case strings.ToUpper(Memory.String()):

libpod/events/logfile.go

@@ -12,6 +12,7 @@ import (
 	"io/ioutil"
 	"os"
 	"path"
+	"path/filepath"
 	"time"
 
 	"github.com/containers/podman/v4/pkg/util"
@@ -27,6 +28,21 @@ type EventLogFile struct {
 	options EventerOptions
 }
 
+// newLogFileEventer creates a new EventLogFile eventer
+func newLogFileEventer(options EventerOptions) (*EventLogFile, error) {
+	// Create events log dir
+	if err := os.MkdirAll(filepath.Dir(options.LogFilePath), 0700); err != nil {
+		return nil, fmt.Errorf("creating events dirs: %w", err)
+	}
+	// We have to make sure the file is created otherwise reading events will hang.
+	// https://github.com/containers/podman/issues/15688
+	fd, err := os.OpenFile(options.LogFilePath, os.O_RDONLY|os.O_CREATE, 0700)
+	if err != nil {
+		return nil, err
+	}
+	return &EventLogFile{options: options}, fd.Close()
+}
+
 // Writes to the log file
 func (e EventLogFile) Write(ee Event) error {
 	// We need to lock events file
@@ -108,6 +124,8 @@ func (e EventLogFile) Read(ctx context.Context, options ReadOptions) error {
 			}
 		}()
 	}
+	logrus.Debugf("Reading events from file %q", e.options.LogFilePath)
+
 	var line *tail.Line
 	var ok bool
 	for {

libpod/runtime.go

@@ -466,14 +466,6 @@ func makeRuntime(runtime *Runtime) (retErr error) {
 		}
 	}
 
-	// Create events log dir
-	if err := os.MkdirAll(filepath.Dir(runtime.config.Engine.EventsLogFilePath), 0700); err != nil {
-		// The directory is allowed to exist
-		if !errors.Is(err, os.ErrExist) {
-			return fmt.Errorf("creating events dirs: %w", err)
-		}
-	}
-
 	// Get us at least one working OCI runtime.
 	runtime.ociRuntimes = make(map[string]OCIRuntime)
 

test/system/090-events.bats

@@ -147,7 +147,6 @@ function _populate_events_file() {
 
     # Config without a limit
     eventsFile=$PODMAN_TMPDIR/events.txt
-    _populate_events_file $eventsFile
     containersConf=$PODMAN_TMPDIR/containers.conf
     cat >$containersConf <<EOF
 [engine]
@@ -155,6 +154,11 @@ events_logger="file"
 events_logfile_path="$eventsFile"
 EOF
 
+    # Check that a non existing event file does not cause a hang (#15688)
+    CONTAINERS_CONF=$containersConf run_podman events --stream=false
+
+    _populate_events_file $eventsFile
+
     # Create events *without* a limit and make sure that it has not been
     # rotated/truncated.
     contentBefore=$(head -n100 $eventsFile)