594e8f35b4
The test uses a 10ms read timeout to exercise code paths that handle
timed-out reads without throwing C++ exceptions. As part of setup, it
inserts rows and flushes them to two SSTables, then runs a warm-up
SELECT to populate internal caches (e.g. the auth cache) before the
real test begins.
The reason for this warm-up read was the possibility that the first
read does additional operations (such as reading and caching
authentication) that might throw exceptions internally. I couldn't
verify that such exceptions actually happen in today's code, but
they might (re)appear in the future, so we should keep the warm-up
SELECT.
On slow CI machines (aarch64, debug build), that warm-up SELECT can
take longer than 10ms to read from the two SSTables. When it does, the
read times out: the coordinator receives 0 responses from the local
replica within the deadline and propagates a read_timeout_exception.
Since the exception is not caught, it escapes the test lambda, is
logged as "cql env callback failed", and causes Boost.Test to report a
C++ failure at the do_with_cql_env_thread call site. This matches the
CI failure seen in SCYLLADB-1774:
ERROR ... replica_read_timeout_no_exception: cql env callback failed,
error: exceptions::read_timeout_exception (Operation timed out for
replica_read_timeout_no_exception.tbl - received only 0 responses
from 1 CL=ONE.)
The CI log also shows that only 12 reads were admitted (the warm-up
read plus the 11 reads from the two prepare() calls and CREATE/INSERT
statements made earlier), and the current permit was stuck in
need_cpu state -- the reactor hadn't had a chance to schedule the read
before the 10ms window elapsed.
The fix catches read_timeout_exception from the warm-up SELECT and
retries until the read succeeds. The warm-up is required for
correctness: some lazy-init code paths (e.g. auth cache population)
use C++ exceptions for control flow internally. Those exceptions must
be absorbed before the cxx_exceptions baseline is sampled inside
execute_test(); otherwise they would appear in the delta and cause a
false test failure. Simply ignoring a timed-out warm-up is not safe,
because the lazy-init exceptions would then fire during the 1000 test
reads, inflating cxx_exceptions_after relative to
cxx_exceptions_before.
No other calls in setup are susceptible to the 10ms read timeout:
- CREATE KEYSPACE, CREATE TABLE, INSERT, and flush use the write
timeout (10s) and are not reads.
- e.prepare() goes through the query processor without reading table
data, so it is not subject to the read timeout.
- The semaphore manipulation in Test 2 is internal and has no timeout.
- All 1000 reads in execute_test() are expected to fail, so a timeout
there is the happy path, not a failure.
The 10ms timeout itself is fine for the test's purpose: it is
deliberately aggressive so that reads reliably time out on the hot path
being tested. The problem was only that the pre-test warm-up was not
guarded against the same timeout.
Fixes: SCYLLADB-1830
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Closes scylladb/scylladb#29731
(cherry picked from commit 1f15e05946)
Closes scylladb/scylladb#29760
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.