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

Wed Jul 17 13:23:29 UTC 2019

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.

+    // 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.
"""

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
> > > > 