RFR(S): 8227122: [TESTBUG] Create Docker sidecar test cases

Wed Jul 17 20:45:58 UTC 2019

Hi Severin,

    Thank you for the review.

On 7/17/19 6:23 AM, Severin Gehwolf wrote:
> Hi Misha,
>
> On Tue, 2019-07-16 at 09:48 -0700, mikhailo.seledtsov at oracle.com wrote:
>> Hi Severin, Bob,
>>
>>      Here is an updated webrev that should address all of your feedback:
>>
>>       http://cr.openjdk.java.net/~mseledtsov/8227122.01/
>>
>> To summarize the changes since webrev 00:
>>
>>        - using 'docker ps' to wait until the "main" container starts
>>
>>        - removed use of --ipc=shareable (not needed)
>>
>>        - added comments regarding sharing of /tmp
>>
>>        - using docker volumes ("--volumes-from") to share /tmp between
>> the containers instead of mapping to host directories (avoids potential
>> access/permission problems)
>>
>>        - few other minor changes and cleanup
> Looks good. A few nits:
>
> +    static class DockerThread extends Thread {
> +        DockerRunOptions runOpts;
> +        OutputAnalyzer out;
>
> 'out' instance variable is never used and could get removed. I don't
> need to see another webrev for this.
Removed.
> +    // The "sidecar" container shares "/tmp" directory with the "main" container for the
> +    // JVM attach mechanism to work. JCMD relies on the attach mechanism (com.sun.tools.attach),
> +    // which in turn relies on JVMSTAT mechanism, which uses Unix socket file hsperf_<pid> residing in
> +    // the /tmp directory.
>
> I'd rephrase the last sentense to:
>
> """
> JCMD relies on the attach mechanism (com.sun.tools.attach),
> which in turn relies on JVMSTAT mechanism, which puts its mapped
> buffers in /tmp directory (hsperfdata_<user>). Thus, we mount /tmp via
> --volumes-from from the main container.
> """

I have updated the comments.

Thank you,

Misha

> Thanks,
> Severin
>
>> Testing:
>>
>>        ran this test on OL 7.6 and on variety of Linux nodes in the lab,
>> a number of times - all PASS
>>
>>
>> See more of comments inline below
>>
>> On 7/12/19 2:12 AM, Severin Gehwolf wrote:
>>> Hi Misha,
>>>
>>> On Thu, 2019-07-11 at 17:58 -0700, mikhailo.seledtsov at oracle.com wrote:
>>>> Hi Severin,
>>>>
>>>>      Thank you for taking a look at this change.
>>>>
>>>> On 7/10/19 10:40 AM, Severin Gehwolf wrote:
>>>>> Hi Misha,
>>>>>
>>>>> On Tue, 2019-07-02 at 15:24 -0700, mikhailo.seledtsov at oracle.com wrote:
>>>>>> Please review this new test that uses a Docker sidecar pattern to
>>>>>> manage/monitor JVM running in the main payload container.
>>>>>>
>>>>>> Sidecar is a common pattern used in the cloud environments for
>>>>>> monitoring among other uses. In side car pattern the main
>>>>>> application/service container that runs the payload is paired with a
>>>>>> sidecar container. It is achieved by sharing certain namespace
>>>>>> aspects
>>>>>> between the two containers such as PID namespace, specific
>>>>>> sub-directories, IPC and more.
>>>>>>
>>>>>> This test implements the following cases:
>>>>>>       - "jcmd -l" to list java processes running in "main" container
>>>>>> from
>>>>>> the "sidecar" container
>>>>>>       - "jhsdb jinfo" in the sidecar configuration
>>>>>>       - jcmd <some-command>
>>>>>>
>>>>>> This change also builds a basis for more test cases in the future.
>>>>>>
>>>>>> Minor changes were done to DockerTestUtils:
>>>>>>       - changing access to DOCKER_COMMAND constant to public
>>>>>>       - minor spelling and terminology corrections
>>>>>>
>>>>>>
>>>>>>         JBS: https://bugs.openjdk.java.net/browse/JDK-8227122
>>>>>>         Webrev: http://cr.openjdk.java.net/~mseledtsov/8227122.00/
>>>>>>         Testing:
>>>>>>             1. ran Docker tests on Linux-x64 - PASS
>>>>>>             2. Running Docker tests in test cluster - in progress
>>>>>>
>>>>> // JCMD does not work in sidecar configuration, except for "jcmd -l".
>>>>> // Including this test case to assist in reproduction of the problem.
>>>>> // t.assertIsAlive();
>>>>> // testCase03(mainProcPid);
>>>>>
>>>>> FWIW, "jcmd -l" doesn't work in this case either. It only sees itself
>>>>> as far as I can tell.
>>>> In my experiment it does work. Here are parts of the test log, first the
>>>> command that runs jcmd in a sidecar container, then the output of that
>>>> container:
>>>>
>>>> """
>>>>
>>>> [COMMAND]
>>>>
>>>> /usr/local/bin/docker run --tty=true --rm --cap-add=SYS_PTRACE
>>>> --sig-proxy=true --pid=container:test-container-main
>>>> --ipc=container:test-container-main -v
>>>> /ws/playArea/sidecar-jcmd-8227122/JTwork/scratch/.:/tmp/
>>>> jdk-internal:test-jfr-jcmd /jdk/bin/jcmd -l
>>>>
>>>> [2019-07-12T00:26:29.083764Z] Gathering output for process 8703
>>>> [ELAPSED: 5 ms]
>>>> [STDERR]
>>>>
>>>> [STDOUT]
>>>> 1 EventGeneratorLoop 15
>>>> 23 jdk.jcmd/sun.tools.jcmd.JCmd -l
>>>>
>>>> """
>>>>
>>>> The output shows 2 processes, one is EventGeneratorLoop with PID of 1
>>>> (as expected). This is possible because the containers share certain
>>>> namespaces and mounted volumes in a 'sidecar' configuration. In this
>>>> case, containers share the PID namespace
>>>> (--pid=container:test-container-main) and share volumes mounted as
>>>> "/tmp" inside the container (-v
>>>> /ws/playArea/sidecar-jcmd-8227122/JTwork/scratch/.:/tmp/)
>>>>
>>> Right, sorry. Perhaps this code should get a comment that sharing /tmp
>>> between sidecar and host container is needed for jvmstat - used
>>> internally by the attach mechanism - to work. See
>>> HotSpotAttachProvider.testAttachable():
>>>
>>> +        String[] command = new String[] {
>>> +            DockerTestUtils.DOCKER_COMMAND, "run",
>>> +            "--tty=true", "--rm",
>>> +            "--cap-add=SYS_PTRACE", "--sig-proxy=true",
>>> +            "--pid=container:" + MAIN_CONTAINER_NAME,
>>> +            "--pid=container:" + MAIN_CONTAINER_NAME,
>>> +            "--ipc=container:" + MAIN_CONTAINER_NAME,
>>> +            "-v", WORK_DIR + ":/tmp/",
>>>
>>> I believe -XX:+UsePerfData would be in order too as I don't think
>>> things would work if that default changed.
>> I have added the comments and added -XX:+UsePerfData for the "main" JVM
>> process.
>>>>> What's more, this seems to be a case of AttachListener::is_init_trigger[1] and
>>>>> VirtualMachineImpl.createAttachFile[2] disagreeing. The former looks in
>>>>> $(pwd)/.attach_pid<pid> or /tmp/.attach_pid<pid> and the latter creates
>>>>> it in /proc/<pid>/root/tmp/.attach_pid<ns_pid>.
>>> This seems to be the cause for why testCase03 doesn't work. Perhaps
>>> this deserves a bug and I can help fix it.
>>>
>>> While looking at that, I discovered what I said below, which is a
>>> different case I know.
>> Once these tests are integrated I will file a bug, and can reference the
>> test from that bug.
>>>>> There seems to be more issues involved. As attaching to a JVM inside a
>>>>> container doesn't seem to work from outside which is supposed to be
>>>>> fixed with JDK-8179498. That alone seems to warrant a bug.
>>>> You are describing a slightly different use case / pattern, but I agree
>>>> it does not seem to work. I am happy to hear confirmation of that.
>>> I was pointing out that JDK-8179498 seems to have regressed. It's
>>> unrelated but should be taken into account when fixing the above issue.
>>>
>>>> The pattern addressed in this test is a side car, where both the
>>>> observer and observee run in containers; the containers are 'friendly'
>>>> by sharing certain apsects of namespaces.
>>> Yes.
>>>
>>>> The use case you are describing is somewhat different, if I understand
>>>> correctly: the observer runs on a host machine, and obsrvee runs in a
>>>> container. Observer tries to use jcmd to list the java processes running
>>>> in container(s), and issue commands, but that fails. I can create a bug
>>>> for that, and a simple test case.
>>> There should be a bug and a test so that it cannot again regress.
>>>
>>> JDK-8193710 is also related, but the fix for that bug didn't have a
>>> test either :( That's this one which needs fixing:
>>> https://bugs.openjdk.java.net/browse/JDK-8195809
>>       JDK-8195809: [TESTBUG] Create tests for JDK-8193710 jps and jcmd -l
>> support for Docker containers
>>
>>       I have assigned it to myself, and will be working on it soon.
>>
>>
>> Thank you,
>>
>> Misha
>>
>>>>>        private static DockerThread startMainContainer() throws Exception {
>>>>>            // start "main" container (the observee)
>>>>>            DockerRunOptions opts = commonDockerOpts("EventGeneratorLoop");
>>>>>            opts.addDockerOpts("--cap-add=SYS_PTRACE", "--ipc=shareable")
>>>>>
>>>>> Is '--ipc=shareable' really needed? It's not a supported option for my
>>>>> docker here :-(
>>>> I have removed the '--ipc=shareable' and the test still works. I think
>>>> this is extra stuff that is not necessary for this test case, so I will
>>>> remove it.
>>> Excellent!
>>>
>>>> I will incorporate changes from your and Bob's review, run some testing,
>>>> and post an updated webrev.
>>> Thanks,
>>> Severin
>>>
>>>>> [1] http://hg.openjdk.java.net/jdk/jdk/file/ba72dac556c3/src/hotspot/os/linux/attachListener_linux.cpp#l500
>>>>> [2] http://hg.openjdk.java.net/jdk/jdk/file/ba72dac556c3/src/jdk.attach/linux/classes/sun/tools/attach/VirtualMachineImpl.java#l295
>>>>>