d8b283e1fb
In this series we add support for forwarding strongly consistent CQL requests to suitable replicas, so that clients can issue reads/writes to any node and have the request executed on an appropriate tablet replica (and, for writes, on the Raft leader). We return the same CQL response as what the user would get while sending the request to the correct replica and we perform the same logging/stats updates on the request coordinator as if the coordinator was the appropriate replica. The core mechanism of forwarding a strongly consistent request is sending an RPC containing the user's cql request frame to the appropriate replica and returning back a ready, serialized `cql_transport::response`. We do this in the CQL server - it is most prepared for handling these types and forwarding a request containing a CQL frame allows us to reuse near-top-level methods for CQL request handling in the new RPC handler (such as the general `process`) For sending the RPC, the CQL server needs to obtain the information about who should it forward the request to. This requires knowledge about the tablet raft group members and leader. We obtain this information during the execution of a `cql3/strong_consistency` statement, and we return this information back to the CQL server using the generalized `bounce_to_shard` `response_message`, where we now store the information about either a shard, or a specific replica to which we should forward to. Similarly to `bounce_to_shard`, we need to handle this `result_message` in a loop - a replica may move during statement execution, or the Raft leader can change. We also use it for forwarding strongly consistent writes when we're not a member of the affected tablet raft group - in that case we need to forward the statement twice - once to any replica of the affected tablet, then that replica can find the leader and return this information to the coordinator, which allows the second request to be directed to the leader. This feature also allows passing through exception messages which happened on the target replica while executing the statement. For that, many methods of the `cql_transport::cql_server::connection` for creating error responses needed to be moved to `cql_transport::cql_server`. And for final exception handling on the coordinator, we added additional error info to the RPC response, so that the handling can be performed without having the `result_message::exception` or `exception_ptr` itself. Fixes [SCYLLADB-71](https://scylladb.atlassian.net/browse/SCYLLADB-71) [SCYLLADB-71]: https://scylladb.atlassian.net/browse/SCYLLADB-71?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ Closes scylladb/scylladb#27517 * github.com:scylladb/scylladb: test: add tests for CQL forwarding transport: enable CQL forwarding for strong consistency statements transport: add remote statement preparation for CQL forwarding transport: handle redirect responses in CQL forwarding transport: add exception handling for forwarded CQL requests transport: add basic CQL request forwarding idl: add a representation of client_state for forwarding cql_server: handle query, execute, batch in one case transport: inline process_on_shard in cql_server::process transport: extract process() to cql_server transport: add messaging_service to cql_server transport: add response reconstruction helpers for forwarding transport: generalize the bounce result message for bouncing to other nodes strong consistency: redirect requests to live replicas from the same rack transport: pass foreign_ptr into sleep_until_timeout_passes and move it to cql_server transport: extract the error handling from process_request_one transport: move error response helpers from connection to cql_server
Scylla unit tests using C++ and the Boost test framework
The source files in this directory are Scylla unit tests written in C++ using the Boost.Test framework. These unit tests come in three flavors:
-
Some simple tests that check stand-alone C++ functions or classes use Boost's
BOOST_AUTO_TEST_CASE. -
Some tests require Seastar features, and need to be declared with Seastar's extensions to Boost.Test, namely
SEASTAR_TEST_CASE. -
Even more elaborate tests require not just a functioning Seastar environment but also a complete (or partial) Scylla environment. Those tests use the
do_with_cql_env()ordo_with_cql_env_thread()function to set up a mostly-functioning environment behaving like a single-node Scylla, in which the test can run.
While we have many tests of the third flavor, writing new tests of this type should be reserved to white box tests - tests where it is necessary to inspect or control Scylla internals that do not have user-facing APIs such as CQL. In contrast, black-box tests - tests that can be written only using user-facing APIs, should be written in one of newer test frameworks that we offer - such as test/cqlpy or test/alternator (in Python, using the CQL or DynamoDB APIs respectively) or test/cql (using textual CQL commands), or - if more than one Scylla node is needed for a test - using the test/topology* framework.
Running tests
Because these are C++ tests, they need to be compiled before running.
To compile a single test executable row_cache_test, use a command like
ninja build/dev/test/boost/row_cache_test
You can also use ninja dev-test to build all C++ tests, or use
ninja deb-build to build the C++ tests and also the full Scylla executable
(however, note that full Scylla executable isn't needed to run Boost tests).
Replace "dev" by "debug" or "release" in the examples above and below to use the "debug" build mode (which, importantly, compiles the test with ASAN and UBSAN enabling on and helps catch difficult-to-catch use-after-free bugs) or the "release" build mode (optimized for run speed).
To run an entire test file row_cache_test, including all its test
functions, use a command like:
build/dev/test/boost/row_cache_test -- -c1 -m1G
to run a single test function test_reproduce_18045() from the longer test
file, use a command like:
build/dev/test/boost/row_cache_test -t test_reproduce_18045 -- -c1 -m1G
In these command lines, the parameters before the -- are passed to
Boost.Test, while the parameters after the -- are passed to the test code,
and in particular to Seastar. In this example Seastar is asked to run on one
CPU (-c1) and use 1G of memory (-m1G) instead of hogging the entire
machine. The Boost.Test option -t test_reproduce_18045 asks it to run just
this one test function instead of all the test functions in the executable.
Unfortunately, interrupting a running test with control-C while doesn't
work. This is a known bug (#5696). Kill a test with SIGKILL (-9) if you
need to kill it while it's running.
Boost tests can also be run using test.py - which is a script that provides a uniform way to run all tests in scylladb.git - C++ tests, Python tests, etc.
Execution with pytest
To run all tests with pytest execute
pytest test/boost
To execute all tests in one file, provide the path to the source filename as a parameter
pytest test/boost/aggregate_fcts_test.cc
Since it's a normal path, autocompletion works in the terminal out of the box.
To execute only one test function, provide the path to the source file and function name
pytest --mode dev test/boost/aggregate_fcts_test.cc::test_aggregate_avg
To provide a specific mode, use the next parameter --mode dev,
if parameter isn't provided pytest tries to use ninja mode_list to find out the compiled modes.
Parallel execution is controlled by pytest-xdist and the parameter -n auto.
This command starts tests with the number of workers equal to CPU cores.
The useful command to discover the tests in the file or directory is
pytest --collect-only -q --mode dev test/boost/aggregate_fcts_test.cc
That will return all test functions in the file.
To execute only one function from the test, you can invoke the output from the previous command.
However, suffix for mode should be skipped.
For example,
output shows in the terminal something like this test/boost/aggregate_fcts_test.cc::test_aggregate_avg.dev.
So to execute this specific test function, please use the next command
pytest --mode dev test/boost/aggregate_fcts_test.cc::test_aggregate_avg
Writing tests
Because of the large build time and build size of each separate test executable, it is recommended to put test functions into relatively large source files. But not too large - to keep compilation time of a single source file (during development) at reasonable levels.
When adding new source files in test/boost, don't forget to list the new source file in configure.py and also in CMakeLists.txt. The former is needed by our CI, but the latter is preferred by some developers.