Add protocol exception tests that check errors and exceptions.
`test_process_startup_invalid_string_map`: `STARTUP` (0x01) with declared
map count, but missing entries - `read_string_map` out-of-range.
`test_process_query_internal_malformed_query`: `QUERY` (0x07) long string
declared larger than available bytes - `read_long_string_view`.
`test_process_query_internal_fail_read_options`: `QUERY` (0x07) with
`PAGE_SIZE` flag, but truncated page_size - `read_options` path.
`test_process_prepare_malformed_query`: `PREPARE` (0x09) long string declared
larger than available bytes - `read_long_string_view` in prepare.
`test_process_execute_internal_malformed_cache_key`: `EXECUTE` (0x0A) cache key
short bytes declared larger than provided bytes - `read_short_bytes`.
`test_process_register_malformed_string_list`: `REGISTER` (0x0B) string list
with truncated element - `read_string_list`/`read_string`.
Each test asserts an `ERROR` frame is returned and `protocol_error` metrics
increase, without causing C++ exceptions.
Refs: #24567
Frame building is repetitive and increases verbosity, reducing code readability.
This patch solves it by extracting common functionality of frame building into
`_build_frame`. Also, helpers `_send_frame` and `_recv_frame` are introduced.
While `_recv_frame` is not really useful, it goes well in pair with `_send_frame`.
Refs: #24567
The code that measures errors and exceptions in `test_protocol_exceptions.py` tests
is repetitive. This patch refactors common functionality in a separate `_test_impl`
function, improving readability.
Refs: #24567
Add `test_unknown_compression_algorithm` test case to `test_protocol_exceptions.py` test suite.
This change improves test coverage for zero throws protocol exception handling.
Refs: #24567
Tested code paths should not throw exceptions. `scylla_reactor_cpp_exceptions`
metric is used. This is a global metric. To address potential test flakiness,
each test runs multiple times:
- `run_count = 100`
- `cpp_exception_threshold = 10`
If a change in the code introduced an exception, expectation is that the number
of registered exceptions will be > `cpp_exception_threshold` in `run_count` runs.
In which case the test fails.
Add a helper to fetch scylla_transport_cql_errors_total{type="protocol_error"} counter
from Scylla's metrics endpoint. These metrics are used to track protocol error
count before and after each test.
Add cql_with_protocol context manager utility for session creation with parameterized
protocol_version value. This is used for testing connection establishment with
different protocol versions, and proper disposal of successfully established sessions.
The tests cover two failure scenarios:
- Protocol version mismatch in test_protocol_version_mismatch which tests both supported
and unsupported protocol version
- Malformed frames via raw socket in _protocol_error_impl, used by several test functions,
and also test_no_protocol_exceptions test to assert that the error counters never decrease
during test execution, catching unintended metric resets
Refs: #24567
