code: def test_log_monitor_update_backpressure(tmp_path, mock_timer):
      log_dir = tmp_path / "logs"
      log_dir.mkdir()
      mock_publisher = MagicMock()
      log_monitor = LogMonitor(
          "127.0.0.1",
          str(log_dir),
          mock_publisher,
          lambda _: True,
          max_files_open=5,
      )
  
      current = 0
      mock_timer.return_value = current
  
      log_monitor.log_filenames = []
      # When threshold < RAY_LOG_MONITOR_MANY_FILES_THRESHOLD, update should happen.
      assert log_monitor.should_update_filenames(current)
      # Add a new file.
      log_monitor.log_filenames = [
          "raylet.out"
          for _ in range(RAY_LOG_MONITOR_MANY_FILES_THRESHOLD)
      ]
      # If the threshold is met, we should update the file after
      # LOG_NAME_UPDATE_INTERVAL_S.
      assert not log_monitor.should_update_filenames(current)
      mock_timer.return_value = LOG_NAME_UPDATE_INTERVAL_S - 0.1
      assert not log_monitor.should_update_filenames(current)
      mock_timer.return_value = LOG_NAME_UPDATE_INTERVAL_S
      assert not log_monitor.should_update_filenames(current)
      mock_timer.return_value = LOG_NAME_UPDATE_INTERVAL_S + 0.1
      assert log_monitor.should_update_filenames(current)
  
imports: import io
  import os
  import re
  import subprocess
  import sys
  import tempfile
  import time
  import logging
  from collections import Counter, defaultdict
  from contextlib import redirect_stderr, redirect_stdout
  from pathlib import Path
  from unittest.mock import Mock, MagicMock
  import pytest
  import ray
  from ray._private import ray_constants
  from ray._private.log_monitor import LOG_NAME_UPDATE_INTERVAL_S, RAY_LOG_MONITOR_MANY_FILES_THRESHOLD, LogFileInfo, LogMonitor, is_proc_alive
  from ray._private.test_utils import get_log_batch, get_log_message, get_log_data, init_log_pubsub, run_string_as_driver, wait_for_condition
  from ray.cross_language import java_actor_class
  from ray.autoscaler._private.cli_logger import cli_logger
label_desc: Use image node_id 19 for calling a global function with example usage: test_log_monitor_update_backpressure(tmp_path, mock_timer) without return types