4810937ddf
The Alternator test test_metrics.py::test_item_latency confirms that
for several operation types (PutItem, GetItem, DeleteItem, UpdateItem)
we did not forget to measure their latencies.
The test checked that a latency was updated by checking that two metrics
increases:
scylla_alternator_op_latency_count
scylla_alternator_op_latency_sum
However, it turns out that the "sum" is only an approximate sum of all
latencies, and when the total sum grows large it sometimes does *not*
increase when a short latency is added to the statistics. When this
happens, this test fails on the assertion that the "sum" increases after
an operation. We saw this happening sometimes in CI runs.
The simple fix is to stop checking _sum at all, and only verify that
the _count increases - this is really an integer counter that
unconditionally increases when a latency is added to the histogram.
Don't worry that the strength of this test is reduced - this test was
never meant to check the accuracy or correctness of the histograms -
we should have different (and better) tests for that, unrelated to
Alternator. The purpose of *this* test is only to verify that for some
specific operation like PutItem, Alternator didn't forget to measure its
latency and update the histogram. We want to avoid a bug like we had
in counters in the past (#9406).
Fixes #18847.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
(cherry picked from commit 13cf6c543d)
Closes scylladb/scylladb#19193
Scylla in-source tests.
For details on how to run the tests, see docs/dev/testing.md
Shared C++ utils, libraries are in lib/, for Python - pylib/
alternator - Python tests which connect to a single server and use the DynamoDB API unit, boost, raft - unit tests in C++ cql-pytest - Python tests which connect to a single server and use CQL topology* - tests that set up clusters and add/remove nodes cql - approval tests that use CQL and pre-recorded output rest_api - tests for Scylla REST API Port 9000 scylla-gdb - tests for scylla-gdb.py helper script nodetool - tests for C++ implementation of nodetool
If you can use an existing folder, consider adding your test to it. New folders should be used for new large categories/subsystems, or when the test environment is significantly different from some existing suite, e.g. you plan to start scylladb with different configuration, and you intend to add many tests and would like them to reuse an existing Scylla cluster (clusters can be reused for tests within the same folder).
To add a new folder, create a new directory, and then
copy & edit its suite.ini.