SmtpClientTest.SendMail_SendQUITOnDispose timeout on OSX

[antonfirsov]

Test case

System.Net.Mail.Tests.SmtpClientTest.SendMail_SendQUITOnDispose(asyncSend: True)
System.Net.Mail.Tests.SmtpClientTest.SendMail_SendQUITOnDispose(asyncSend: False)

Failed on

net5.0-OSX-Debug-x64-CoreCLR_release-OSX.1014.Amd64.Open
https://dev.azure.com/dnceng/public/_build/results?buildId=796625&view=ms.vss-test-web.build-test-results-tab&runId=25205974&paneView=debug&resultId=167484

With

System.TimeoutException : Task timed out after 00:00:30

Stack trace

at System.Threading.Tasks.TaskTimeoutExtensions.TimeoutAfter(Task task, TimeSpan timeout) in /_/src/libraries/Common/tests/System/Threading/Tasks/TaskTimeoutExtensions.cs:line 41
   at System.Net.Mail.Tests.SmtpClientTest.SendMail_SendQUITOnDispose(Boolean asyncSend) in /_/src/libraries/System.Net.Mail/tests/Functional/SmtpClientTest.cs:line 512

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[wfurt]

I hit that as well. I'm wondering if this is related to #41508. We did not see that before AFAIK.

cc: @tmds

[wfurt]

4 failures in last 4 days and nothing before in 90 days. This looks like regression @karelz

[tmds]

This is the test that fails, for asyncSend=true.

        [Theory]
        [InlineData(false)]
        [InlineData(true)]
        public async Task SendMail_SendQUITOnDispose(bool asyncSend)
        {
            bool quitMessageReceived = false;
            using ManualResetEventSlim quitReceived = new ManualResetEventSlim();
            using var server = new LoopbackSmtpServer();
            server.OnQuitReceived += _ =>
            {
                quitMessageReceived = true;
                quitReceived.Set();
            };

            using (SmtpClient client = server.CreateClient())
            {
                client.Credentials = new NetworkCredential("Foo", "Bar");
                MailMessage msg = new MailMessage("foo@example.com", "bar@example.com", "hello", "howdydoo");
                if (asyncSend)
                {
                    await client.SendMailAsync(msg).TimeoutAfter((int)TimeSpan.FromSeconds(30).TotalMilliseconds);
                }
                else
                {
                    client.Send(msg);
                }
                Assert.False(quitMessageReceived, "QUIT received");
            }

            // There is a latency between send/receive.
            quitReceived.Wait(TimeSpan.FromSeconds(30));
            Assert.True(quitMessageReceived, "QUIT message not received");
        }

From the exception, it seems it is throwing on TimeoutAfter.

4 failures in last 4 days and nothing before in 90 days. This looks like regression @karelz

#41508 matches the timing. #41508 should only be changing behaviour when the Socket gets cleaned up by the finalizer. I don't think that happens in this test.

This was reported against macOS, has it occurred on Linux? I will try to reproduce it on Linux.

Maybe we need to increase the timeout used?

[wfurt]

All cases I saw were on OSX 10.14. I don't see direct correlation either but it is suspicious that the test verifies dispose behavior. I'm wondering if all this is timing....? But I don't know why it would be much? slower.

[antonfirsov]

What I see in Kusto, querying for Method == "SendMail_SendQUITOnDispose":

• There are 5 failures since 2020-08-28, 2 with asyncSend: true and 3 with asyncSend: false. The test did not fail before.
• The sync variant fails in client.Send(msg), the async variant fails in quitReceived.Wait(TimeSpan.FromSeconds(30))
• The following 2 failures happened before merging SafeSocketHandle: avoid potential blocking of finalizer thread #41508 (which was around 2020-09-01 12:00 UTC):
  

[karelz]

Triage: Check if it was 1 machine? Or if there are more random test failures on the OSX 10.14.
Let's keep it in 5.0 until we are sure it is NOT impacting production of 5.0, given it started failing just recently -- we don't want to punt it until we are sure it is not a regression in 5.0.

[wfurt]

I did 1000+ runs locally and I did not see any failure.

[CarnaViire]

I also wasn't able to repro it locally.
And we didn't have any additional failures for this test since 2020-09-01 18:56.

Also, querying for long timeouted tests in last month shows me that this number is pretty high for osx.1014.amd64.open (it took the first place)

QueueName	Count
osx.1014.amd64.open	1819
windows.10.amd64.open	634
ubuntu.1604.amd64.open	480
...	...

link to Kusto

Query that I ran

Details

TestResults 
| join kind=inner WorkItems on WorkItemId 
| join kind=inner Jobs on JobId
| where Finished >= datetime(2020-08-04) and Message contains 'timeout' and Result == 'Fail' and Duration > 30
| summarize Count = count() by QueueName
| order by Count desc
| project QueueName, Count

It makes me think that it might be CI overload for Mac machines...