e9944f0b7c
Merge co-location can emit migrations across racks even when RF=#racks, reducing availability and affecting consistency of base-view pairing. Given replica set of sibling tablets T0 and T1 below: [T0: (rack1,rack3,rack2)] [T1: (rack2,rack1,rack3)] Merge will co-locate T1:rack2 into T0:rack1, T1 will be temporarily only at only a subset of racks, reducing availability. This is the main problem fixed by this patch. It also lays the ground for consistent base-view replica pairing, which is rack-based. For tables on which views can be created we plan to enforce the constraint that replicas don't move across racks and that all tablets use the same set of racks (RF=#racks). This patch avoids moving replicas across racks unless it's necessary, so if the constraint is satisfied before merge, there will be no co-locating migrations across racks. This constraint of RF=#racks is not enforced yet, it requires more extensive changes. Fixes #22994. Refs #17265. This patch is based on Raphael's work done in PR #23081. The main differences are: 1) Instead of sorting replicas by rack, we try to find replicas in sibling tablets which belong to the same rack. This is similar to how we match replicas within the same host. It reduces number of across-rack migrations even if RF!=#racks, which the original patch didn't handle. Unlike the original patch, it also avoids rack-overloaded in case RF!=#racks 2) We emit across-rack co-locating migrations if we have no other choice in order to finalize the merge This is ok, since views are not supported with tablets yet. Later, we will disallow this for tables which have views, and we will allow creating views in the first place only when no such migrations can happen (RF=#racks). 3) Added boost unit test which checks that rack overload is avoided during merge in case RF<#racks 4) Moved logging of across-rack migration to debug level 5) Exposed metric for across-rack co-locating migrations Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com> Signed-off-by: Tomasz Grabiec <tgrabiec@scylladb.com> Closes scylladb/scylladb#23247
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.