read_failures_test.py

import logging
import pytest

from cassandra import ConsistencyLevel, ReadFailure, ReadTimeout
from cassandra.policies import FallthroughRetryPolicy
from cassandra.query import SimpleStatement

from dtest import Tester

since = pytest.mark.since
logger = logging.getLogger(__name__)

KEYSPACE = "readfailures"


class TestReadFailures(Tester):
    """
    Tests for read failures in the replicas, introduced as a part of
    @jira_ticket CASSANDRA-12311.
    """
    @pytest.fixture(autouse=True)
    def fixture_add_additional_log_patterns(self, fixture_dtest_setup):
        fixture_dtest_setup.ignore_log_patterns = (
            "Scanned over [1-9][0-9]* tombstones",  # This is expected when testing read failures due to tombstones
        )
        return fixture_dtest_setup

    @pytest.fixture(scope='function', autouse=True)
    def fixture_dtest_setup_params(self):
        self.tombstone_failure_threshold = 500
        self.replication_factor = 3
        self.consistency_level = ConsistencyLevel.ALL
        self.expected_expt = ReadFailure

    def _prepare_cluster(self):
        self.cluster.set_configuration_options(
            values={'tombstone_failure_threshold': self.tombstone_failure_threshold}
        )
        self.cluster.populate(3)
        self.cluster.start()
        self.nodes = list(self.cluster.nodes.values())

        session = self.patient_exclusive_cql_connection(self.nodes[0], protocol_version=self.protocol_version)

        session.execute("""
            CREATE KEYSPACE IF NOT EXISTS %s
            WITH replication = { 'class': 'SimpleStrategy', 'replication_factor': '%s' }
            """ % (KEYSPACE, self.replication_factor))
        session.set_keyspace(KEYSPACE)
        session.execute("CREATE TABLE IF NOT EXISTS tombstonefailure (id int, c int, value text, primary key(id, c))")

        return session

    def _insert_tombstones(self, session, number_of_tombstones):
        for num_id in range(number_of_tombstones):
            session.execute(SimpleStatement("DELETE value FROM tombstonefailure WHERE id = 0 and c = {}".format(num_id),
                                            consistency_level=self.consistency_level, retry_policy=FallthroughRetryPolicy()))

    def _perform_cql_statement(self, session, text_statement):
        statement = SimpleStatement(text_statement,
                                    consistency_level=self.consistency_level,
                                    retry_policy=FallthroughRetryPolicy())

        if self.expected_expt is None:
            session.execute(statement)
        else:
            with pytest.raises(self.expected_expt) as cm:
                # On 2.1, we won't return the ReadTimeout from coordinator until actual timeout,
                # so we need to up the default timeout of the driver session
                session.execute(statement, timeout=15)
            return cm._excinfo[1]

    def _assert_error_code_map_exists_with_code(self, exception, expected_code):
        """
        Asserts that the given exception contains an error code map
        where at least one node responded with some expected code.
        This is meant for testing failure exceptions on protocol v5.
        """
        assert exception is not None
        assert exception.error_code_map is not None
        expected_code_found = False
        for error_code in list(exception.error_code_map.values()):
            if error_code == expected_code:
                expected_code_found = True
                break
        assert expected_code_found, "The error code map did not contain " + str(expected_code)

    @since('2.1')
    def test_tombstone_failure_v3(self):
        """
        A failed read due to tombstones at v3 should result in a ReadTimeout
        """
        self.protocol_version = 3
        self.expected_expt = ReadTimeout
        session = self._prepare_cluster()
        self._insert_tombstones(session, 600)
        self._perform_cql_statement(session, "SELECT value FROM tombstonefailure")

    @since('2.2')
    def test_tombstone_failure_v4(self):
        """
        A failed read due to tombstones at v4 should result in a ReadFailure
        """
        self.protocol_version = 4
        session = self._prepare_cluster()
        self._insert_tombstones(session, 600)
        self._perform_cql_statement(session, "SELECT value FROM tombstonefailure")

    @since('4.0')
    def test_tombstone_failure_v5(self):
        """
        A failed read due to tombstones at v5 should result in a ReadFailure with
        an error code map containing error code 0x0001 (indicating that the replica(s)
        read too many tombstones)
        """
        self.protocol_version = 5
        session = self._prepare_cluster()
        self._insert_tombstones(session, 600)
        exc = self._perform_cql_statement(session, "SELECT value FROM tombstonefailure")
        self._assert_error_code_map_exists_with_code(exc, 0x0001)