db: log full path to WAL file in disk slow info

Log full path to WAL file in disk slow info so it's explicit if the
WAL file is on the primary or secondary.

Fixes #5328

Author: xxmplus

vfs/disk_health.go

@@ -466,15 +466,20 @@ func (i DiskSlowInfo) String() string {
 
 // SafeFormat implements redact.SafeFormatter.
 func (i DiskSlowInfo) SafeFormat(w redact.SafePrinter, _ rune) {
+	fullPath, err := filepath.Abs(i.Path)
+	if err != nil {
+		w.Printf("failed to get absolute path %s: %s", redact.Safe(i.Path), err)
+		fullPath = i.Path
+	}
 	switch i.OpType {
 	// Operations for which i.WriteSize is meaningful.
 	case OpTypeWrite, OpTypeSyncTo, OpTypePreallocate:
 		w.Printf("disk slowness detected: %s on file %s (%d bytes) has been ongoing for %0.1fs",
-			redact.Safe(i.OpType.String()), redact.Safe(filepath.Base(i.Path)),
+			redact.Safe(i.OpType.String()), redact.Safe(fullPath),
 			redact.Safe(i.WriteSize), redact.Safe(i.Duration.Seconds()))
 	default:
 		w.Printf("disk slowness detected: %s on file %s has been ongoing for %0.1fs",
-			redact.Safe(i.OpType.String()), redact.Safe(filepath.Base(i.Path)),
+			redact.Safe(i.OpType.String()), redact.Safe(fullPath),
 			redact.Safe(i.Duration.Seconds()))
 	}
 }

vfs/disk_health_test.go

@@ -635,3 +635,24 @@ func TestDiskHealthChecking_Filesystem_Close(t *testing.T) {
 	}
 	wg.Wait()
 }
+
+func TestDiskSlowInfo(t *testing.T) {
+	info := DiskSlowInfo{
+		Path:      "/some/really/deep/path/to/wal/000123.log",
+		OpType:    OpTypeWrite,
+		WriteSize: 123,
+		Duration:  5 * time.Second,
+	}
+
+	result := info.String()
+
+	// Essential information should be present
+	require.Contains(t, result, "disk slowness detected")
+	require.Contains(t, result, "write")
+	require.Contains(t, result, "/some/really/deep/path/to/wal/000123.log")
+	require.Contains(t, result, "(123 bytes)")
+	require.Contains(t, result, "5.0s")
+
+	// Should not contain just the filename without full path
+	require.NotContains(t, result, " 000123.log ")
+}