code: def test_worker_replica_failure(serve_instance):
      @ray.remote
      class Counter:
          def __init__(self):
              self.count = 0
  
          def inc_and_get(self):
              self.count += 1
              return self.count
  
      @serve.deployment(name="replica_failure")
      class Worker:
          # Assumes that two replicas are started. Will hang forever in the
          # constructor for any workers that are restarted.
          def __init__(self, counter):
              self.should_hang = False
              self.index = ray.get(counter.inc_and_get.remote())
              if self.index > 2:
                  while True:
                      pass
  
          def __call__(self, *args):
              return self.index
  
      counter = Counter.remote()
      serve.run(Worker.options(num_replicas=2).bind(counter))
  
      # Wait until both replicas have been started.
      responses = set()
      start = time.time()
      while time.time() - start < 30:
          time.sleep(0.1)
          response = request_with_retries(
              "/replica_failure/", timeout=1
          ).text
          assert response in ["1", "2"]
          responses.add(response)
          if len(responses) > 1:
              break
      else:
          raise TimeoutError(
              "Timed out waiting for replicas after 30s."
          )
  
      # Kill one of the replicas.
      handles = _get_worker_handles("replica_failure")
      assert len(handles) == 2
      ray.kill(handles[0], no_restart=False)
  
      # Check that the other replica still serves requests.
      for _ in range(10):
          while True:
              try:
                  # The timeout needs to be small here because the request to
                  # the restarting worker will hang.
                  request_with_retries("/replica_failure/", timeout=0.1)
                  break
              except TimeoutError:
                  time.sleep(0.1)
  
file_path: ray/python/ray/serve/tests/test_failure.py
imports: import os
  import sys
  import time
  import pytest
  import requests
  import ray
  from ray import serve
  from ray._private.test_utils import SignalActor, wait_for_condition
  from ray.serve._private.common import DeploymentID
  from ray.serve._private.constants import SERVE_DEFAULT_APP_NAME
label_desc: Use image node_id 7 for calling a global function with example usage: test_worker_replica_failure(serve_instance) and returns: self, self