RFR 8166642: serviceability/dcmd/framework/* timeout

[Chris Plummer]

On 3/13/18 10:54 PM, David Holmes wrote:
> Hi Daniil,
>
> On 14/03/2018 3:26 PM, Daniil Titov wrote:
>> Please review the changes that fix intermittent timeout failure of 
>> serviceability/dcmd/framework/* tests.
>>
>> The problem here is that these tests invoke jcmd in different ways 
>> and one of such ways is when a main class is passed to the jcmd as a 
>> VM identifier. The main class for jtreg test is 
>> com.sun.javatest.regtest.agent.MainWrapper and in some cases more 
>> than one test are running in parallel and there are multiple Java 
>> processes with com.sun.javatest.regtest.agent.MainWrapper as a main 
>> class . When it happens jcmd iterates over all Java processes that 
>> match the condition (the main class equals to 
>> com.sun.javatest.regtest.agent.MainWrapper) and executes the command 
>> for each of them. That results in the jcmd invokes the given command 
>> multiple times and attaches to Java processes not related to the 
>> current test.
>
> It's good to finally find the root cause of the problem!
>
>> The fix makes serviceability/dcmd/framework/* tests non-concurrent to 
>> ensure that they don't interact with other tests.
>
> This seems more of a workaround than a fix - though I don't know 
> whether there is a way to distinguish multiple VMs all running what 
> appears to be the same main class.
The three tests are all intentionally testing the "jcmd <classname>" 
functionality. A better fix (but not worth it IMHO) would be to spawn a 
separate test process rather than using the main test process, which is 
always going to share the main class name with other concurrently 
running tests.
>
> My concern with the fix is how long it will take to run these tests 
> sequentially, as they are run in tier2 and as part of the CI test job?
They are quick tests and there are only 3 of them. They appear to take 
less than 5 seconds each.

Chris
>
> Thanks,
> David
>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8166642
>> Webrev: http://cr.openjdk.java.net/~dtitov/8166642/webrev.01
>>
>> The tests ran successfully with Mach5.
>>
>> Best regards,
>> Daniil
>>
>>