57b24383ed
As seen in #23284, when the tablet_metadata contains many tables, even empty ones, we're seeing a long queue of seastar tasks coming from the individual destruction of `tablet_map_ptr = foreign_ptr<lw_shared_ptr<const tablet_map>>`. This change improves `tablet_metadata::clear_gently` to destroy the `tablet_map_ptr` objects on their owner shard by sorting them into vectors, per- owner shard. Also, background call to clear_gently was added to `~token_metadata`, as it is destroyed arbitrarily when automatic token_metadata_ptr variables go out of scope, so that the contained tablet_metadata would be cleared gently. Finally, a unit test was added to reproduce the `Too long queue accumulated for gossip` symptom and verify that it is gone with this change. Fixes #24814 Refs #23284 This change is not marked as fixing the issue since we still need to verify that there is no impact on query performance, reactor stalls, or large allocations, with a large number of tablet-based tables. * Since the issue exists in 2025.1, requesting backport to 2025.1 and upwards - (cherry picked from commit3acca0aa63) - (cherry picked from commit493a2303da) - (cherry picked from commite0a19b981a) - (cherry picked from commit2b2cfaba6e) - (cherry picked from commit2c0bafb934) - (cherry picked from commit4a3d14a031) - (cherry picked from commit6e4803a750) Parent PR: #24618 Closes scylladb/scylladb#24862 * github.com:scylladb/scylladb: token_metadata_impl: clear_gently: release version tracker early test: topology_custom: test_tablets_merge: add test_tablet_split_merge_with_many_tables token_metadata: clear_and_destroy_impl when destroyed token_metadata: keep a reference to shared_token_metadata token_metadata: move make_token_metadata_ptr into shared_token_metadata class replica: database: get and expose a mutable locator::shared_token_metadata locator: tablets: tablet_metadata: clear_gently: optimize foreign ptr destruction
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.