76cf5148e1
This is a forward port (from scylla-enterprise) of additional compression options (zstd, dictionaries shared across messages) for inter-node network traffic. It works as follows: After the patch, messaging_service (Scylla's interface for all inter-node communication) compresses its network traffic with compressors managed by the new advanced_rpc_compression::tracker. Those compressors compress with lz4, but can also be configured to use zstd as long as a CPU usage limit isn't crossed. A precomputed compression dictionary can be fed to the tracker. Each connection handled by the tracker will then start a negotiation with the other end to switch to this dictionary, and when it succeeds, the connection will start being compressed using that dictionary. All traffic going through the tracker is passed as a single merged "stream" through dict_sampler. dictionary_service has access to the dict_sampler. On chosen nodes (in the "usual" configuration: the Raft leader), it uses the sampler to maintain a random multi-megabyte sample of the sampler's stream. Every several minutes, it copies the sample, trains a compression dictionary on it (by calling zstd's training library via the alien_worker thread) and publishes the new dictionary to system.dicts via Raft's write_mutation command. This update triggers (eventually) a callback on all nodes, which feeds the new dictionary to advanced_rpc_compression::tracker, and this switches (eventually) all inter-node connections to this dictionary. Closes scylladb/scylladb#22032 * github.com:scylladb/scylladb: messaging_service: use advanced_rpc_compression::tracker for compression message/dictionary_service: introduce dictionary_service service: make Raft group 0 aware of system.dicts db/system_keyspace: add system.dicts utils: add advanced_rpc_compressor utils: add dict_trainer utils: introduce reservoir_sampling utils: introduce alien_worker utils: add stream_compressor
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.
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.