c06e63daed
This patch series contains the following changes: - Incorporation of `crypt_sha512.c` from musl to out codebase - Conversion of `crypt_sha512.c` to C++ and coroutinization - Coroutinization of `auth::passwords::check` - Enabling use of `__crypt_sha512` orignated from `crypt_sha512.c` for computing SHA 512 passwords of length <=255 - Addition of yielding in the aforementioned hashing implementation. The alien thread was a solution for reactor stalls caused by indivisible password‑hashing tasks (https://github.com/scylladb/scylladb/issues/24524). However, because there is only one alien thread, overall hashing throughput was reduced (see, e.g., https://github.com/scylladb/scylla-enterprise/issues/5711). To address this, the alien‑thread solution is reverted, and a hashing implementation with yielding is introduced in this patch series. Before this patch series, ScyllaDB used SHA-512 hashing provided by the `crypt_r` function, which in our case meant using the implementation from the `libxcrypt` library. Adding yielding to this `libxcrypt` implementation is problematic, both due to licensing (LGPL) and because the implementation is split into many functions across multiple files. In contrast, the SHA-512 implementation from `musl libc` has a more permissive license and is concise, which makes it easier to incorporate into the ScyllaDB codebase. The performance of this solution was compared with the previous implementation that used one alien thread and the implementation after the alien thread was reverted. The results (median) of `perf-cql-raw` with `--connection-per-request 1 --smp 10` parameters are as follows: - Alien thread: 41.5 new connections/s per shard - Reverted alien thread: 244.1 new connections/s per shard - This commit (yielding in hashing): 198.4 new connections/s per shard The roughly 20% performance deterioration compared to the old implementation without the alien thread comes from the fact that the new hashing algorithm implemented in `utils/crypt_sha512.cc` performs an expensive self-verification and stack cleanup. On the other hand, with smp=10 the current implementation achieves roughly 5x higher throughput than the alien thread. In addition, due to yielding added in this commit, the algorithm is expected to provide similar protection from stalls as the alien thread did. In a test that in parallel started a cassandra-stress workload and created thousands of new connections using python-driver, the values of `scylla_reactor_stalls_count` metric were as follows: - Alien thread: 109 stalls/shard total - Reverted alien thread: 13186 stalls/shard total - This commit (yielding in hashing): 149 stalls/shard total Similarly, the `scylla_scheduler_time_spent_on_task_quota_violations_ms` values were: - Alien thread: 1087 ms/shard total - Reverted alien thread: 72839 ms/shard total - This commit (yielding in hashing): 1623 ms/shard total To summarize, yielding during hashing computations achieves similar throughput to the old solution without the alien thread but also prevents stalls similarly to the alien thread. Fixes: scylladb/scylladb#26859 Refs: scylladb/scylla-enterprise#5711 No automatic backport. After this PR is completed, the alien thread should be rather reverted from older branches (2025.2-2025.4 because on 2025.1 it's already removed). Backporting of the other commits needs further discussion. Closes scylladb/scylladb#26860 * github.com:scylladb/scylladb: test/boost: add too_long_password to auth_passwords_test test/boost: add same_hashes_as_crypt_r to auth_passwords_test auth: utils: add yielding to crypt_sha512 auth: change return type of passwords::check to future auth: remove code duplication in verify_scheme test/boost: coroutinize auth_passwords_test utils: coroutinize crypt_sha512 utils: make crypt_sha512.cc to compile utils: license: import crypt_sha512.c from musl to the project Revert "auth: move passwords::check call to alien thread"
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.