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test/boost: fix flaky test node_view_update_backlog

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The boost test view_schema_test.cc::node_view_update_backlog can be
flaky if the test machine has a hiccup of 100ms, and this patch fixes
it:

The test is a unit test for db::view::node_update_backlog, which is
supposed to cache the backlog calculation for a given interval. The
test asks to cache the backlog for 100ms, and then without sleeping
at all tries to fetch a value again and expect the unchanged cached
value to be returned. However, if the test run experiences a context
switch of 100ms, it can fail, and it did once as reported in #27876.

The fix is to change the interval in this test from 100ms to something
much larger, like 10 seconds. We don't sleep this amount - we just need
the second fetch to happen *before* 10 seconds has passed, so there's
no harm in using a very large interval.

However, the second half of this test wants to check that after the
interval is over, we do get a new backlog calculation. So for the
second half of this test we can and should use a shorter backlog -
e.g., 10ms. We don't care if the test machine is slow or context switched,
for this half of the test we want to to sleep *more* than 10ms, and
that's easy.

The fixed test is faster than the old one (10ms instead of 100ms) and
more reliable on a shared test machine.

Fixes #27876.

Signed-off-by: Nadav Har'El <nyh@scylladb.com>

Closes scylladb/scylladb#27878
This commit is contained in:
Nadav Har'El
2025-12-25 16:19:31 +02:00
committed by Patryk Jędrzejczak
parent c9eab7fbd4
commit ffcce1ffc8
1 changed files with 23 additions and 6 deletions
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29
test/boost/view_schema_test.cc
View File

@@ -2599,7 +2599,16 @@ SEASTAR_TEST_CASE(test_unselected_column) {
}
SEASTAR_THREAD_TEST_CASE(node_view_update_backlog) {
db::view::node_update_backlog b(2, 100ms);
// This test was originally written assuming we have (at least) two
// shards and the test doesn't run on shard 1...
BOOST_ASSERT(this_shard_id() != 1);
BOOST_ASSERT(smp::count >= 2);
// First, check that a db::view::node_update_backlog object doesn't
// recalculate the backlog if the interval hasn't yet passed (we use
// a long 10 second interval that will certainly not pass during this
// test).
db::view::node_update_backlog b(2, 10s);
auto backlog = [] (size_t size) { return db::view::update_backlog{size, 1000}; };
smp::submit_to(0, [&b, &backlog] {
b.add(backlog(10));
@@ -2610,12 +2619,20 @@ SEASTAR_THREAD_TEST_CASE(node_view_update_backlog) {
b.fetch();
}).get();
BOOST_REQUIRE(b.load() == backlog(10));
sleep(101ms).get();
smp::submit_to(1, [&b, &backlog] {
b.add(backlog(100));
b.fetch();
// Second, check that the backlog *is* recalculated if the interval
// has passed. We use a very short interval (10ms) and sleep a bit more
// to make sure it has passed.
db::view::node_update_backlog b2(2, 10ms);
smp::submit_to(0, [&b2, &backlog] {
b2.add(backlog(10));
b2.fetch();
}).get();
BOOST_REQUIRE(b.load() == backlog(100));
sleep(11ms).get();
smp::submit_to(1, [&b2, &backlog] {
b2.add(backlog(100));
b2.fetch();
}).get();
BOOST_REQUIRE(b2.load() == backlog(100));
}
SEASTAR_TEST_CASE(hide_ttl_and_writetime_for_virtual_columns) {