Method test_nearest

test/test_read_preferences.py:272–302

(self)

        self.assertReadsFrom("secondary", read_preference=ReadPreference.SECONDARY_PREFERRED)

    def test_nearest(self):
        # With high localThresholdMS, expect to read from any
        # member
        c = self.rs_client(
            read_preference=ReadPreference.NEAREST, localThresholdMS=10000
        )  # 10 seconds

        data_members = {self.client.primary} | self.client.secondaries

        # This is a probabilistic test; track which members we've read from so
        # far, and keep reading until we've used all the members or give up.
        # Chance of using only 2 of 3 members 10k times if there's no bug =
        # 3 * (2/3)**10000, very low.
        used: set = set()
        i = 0
        while data_members.difference(used) and i < 10000:
            address = self.read_from_which_host(c)
            used.add(address)
            i += 1

        not_used = data_members.difference(used)
        latencies = ", ".join(
            "%s: %sms" % (server.description.address, server.description.round_trip_time)
            for server in (c._get_topology()).select_servers(readable_server_selector, _Op.TEST)
        )

        self.assertFalse(
            not_used,
            "Expected to use primary and all secondaries for mode NEAREST,"
            f" but didn't use {not_used}\nlatencies: {latencies}",
        )


class ReadPrefTester(MongoClient):