bereng commented on a change in pull request #870:
URL: https://github.com/apache/cassandra/pull/870#discussion_r573472792
##########
File path:
test/unit/org/apache/cassandra/cql3/validation/operations/AlterTest.java
##########
@@ -269,6 +276,63 @@ public void testCreateAlterKeyspaces() throws Throwable
"max_threshold", "32")));
}
+ @Test
+ public void testCreateAlterKeyspacesRFWarnings() throws Throwable
+ {
+ requireNetwork();
+ Thread.sleep(1000); // Hack: requireNetwork() will clear warnings
async so give some time to complete
Review comment:
Hi,
Thx Andres for multiplexing it but running the method individually won't
repro the issue. I get it, sometimes, only if running the whole class. It
failed only 1 out of 20 for me today whereas it used to fail every time some
days ago...
As I am failing to explain why the polling is wrong let me try to show it
with code assuming `while(warns not empty) sleep(1)`;
- Test method starts and 'requireNetwork()' is called
- Polling loop sees 0 warns so doesn't sleep
- Test runs CQL and a warning is generated
- Some 'requireNetwork' async call clears warnings
- Assert fails as it sees 0 warnings instead of 1
Now we do the same without polling
- Test method starts and 'requireNetwork()' is called
- Sleep(1) + some 'requireNetwork' async call clears warnings hopefully
within the sleep. This is the source of flakiness
- Test runs CQL and a warning is generated
- Assert succeeds
The problem is that waiting for warns to be empty is _not_ what we need. We
need to wait for warns to be stable (aka requireNetwork to have finished
completely). Now you can tell me I should do instead a `do sleep(1)
while(!warns.empty())` and then it will work. But what's the point in polling
on a random variable? It's like polling for pears when you're waiting on
apples. It's the sleep that makes things work, the poll does nothing but
confuse the reader imo.
This is the best I can explain it. If I am not managing to explain it let's
just remove or poll (any of both won't sleep) and then we can fix it when/if it
starts failing in CI.
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