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#
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from __future__ import absolute_import, division, print_function
import pytest

from threading import Thread
from tests.common.custom_cluster_test_suite import CustomClusterTestSuite

# This custom cluster test exercises the behavior of the front end thrift
# server on how a new client connection request is handled, after the maximum
# number of front end service threads (--fe_service_threads) has been
# allocated. If "--accepted_client_cnxn_timeout" > 0, new connection
# requests are rejected if they wait in the accepted queue for more than the
# the specified timeout.
# See IMPALA-7800.


class TestFrontendConnectionLimit(CustomClusterTestSuite):

  @classmethod
  def add_test_dimensions(cls):
    super(TestFrontendConnectionLimit, cls).add_test_dimensions()

  @classmethod
  def need_default_clients(cls):
    """Must not create default clients because it will interfere with test methods.
    """
    return False

  def _connect_and_query(self, query, impalad):
    with impalad.service.create_hs2_client() as client:
      self.execute_query_expect_success(client, query)

  @pytest.mark.execute_serially
  @CustomClusterTestSuite.with_args(
    impalad_args="--fe_service_threads=1 --accepted_client_cnxn_timeout=0")
  def test_no_connection_is_rejected(self):
    """ IMPALA-7800: New connection request should not be rejected if
        --accepted_client_cnxn_timeout=0"""

    query = "select sleep(2000)"
    impalad = self.cluster.get_any_impalad()
    q1 = Thread(target=self._connect_and_query, args=(query, impalad,))
    q2 = Thread(target=self._connect_and_query, args=(query, impalad,))
    q1.start()
    q2.start()
    q1.join()
    q2.join()

  @pytest.mark.execute_serially
  @CustomClusterTestSuite.with_args(
    impalad_args="--fe_service_threads=1 --accepted_client_cnxn_timeout=5000")
  def test_server_busy(self):
    """ IMPALA-7800: Reject new incoming connections if --accepted_client_cnxn_timeout > 0
        and the request spent too much time waiting in the accepted queue."""

    client = self.create_impala_client()
    client.execute_async("select sleep(7000)")

    # This step should fail to open a session.
    # create_impala_client() does not throw an error on connection failure
    # The only way to detect the connection is invalid is to perform a
    # query in it
    client1 = self.create_impala_client()
    caught_exception = False
    try:
      client1.execute("select sleep(8000)")
    except Exception:
      caught_exception = True
    client.close()
    assert caught_exception, 'Query on client1 did not fail as expected'