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From Malcolm McFarland <mmcfarl...@cavulus.com>
Subject Re: Tracing the Samza+YARN startup process
Date Tue, 18 Jun 2019 21:37:36 GMT
Just want to follow up on this, for anybody that might be trying to do
something similar.

There are two things that were getting in the way of us using YARN+Samza on
ECS: 1) YARN needs to be able to resolve its hostname to something that's
publicly available; and 2) Samza needs to be able to open connections on
arbitrary ports in the 30000+ range.

Docker confounds each of these in a different way. For the first, Docker's
hostname inside of the container is an arbitrary hash, and this is what
java.net.InetAddress will resolve to. I took Rayman's suggestion and used
dnsmasq to create a local CNAME mapping inside the container, mapping the
local "hostname" to one that is publicly available. This should work well
for any Docker-hosted JVM app relying on java.net.InetAddress.

Docker also only allows 100 ports to be publicly exposed, and there is no
configuration option in Samza to specify what the range of ports will be.
The way we worked around this on ECS was to create an elastic network
interface (ENI) for each of the node manager containers. Although I can't
find any documentation on this, I suspect that Fargate does this by
default, as the whole point of that service is to bypass the restrictions
placed on containers running on EC2 instances. With the ENI, we no longer
had to explicitly expose any ports; all ports will be available if the
security group allows.

As an aside, you might wonder: why not just run these on Fargate? Well,
Fargate only allows 10GB of storage (this can be extended a small amount
via an ephemeral mounted volume but seemingly not enough to satisfy YARN's
VM requirements).

Hth, and thanks for everybody's patience,

Malcolm McFarland
Cavulus


This correspondence is from HealthPlanCRM, LLC, d/b/a Cavulus. Any
unauthorized or improper disclosure, copying, distribution, or use of the
contents of this message is prohibited. The information contained in this
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please notify the sender immediately and delete the original message.


On Fri, May 31, 2019 at 3:08 PM rayman preet <rayman7718@gmail.com> wrote:

> Apart from /etc/hosts and /bin/hostname the only other relevant place might
> be
> to modify values in /etc/resolv.conf, to point to, e.g., a dnsmasq
> instance.
>
> On Fri, May 31, 2019 at 2:43 PM Malcolm McFarland <mmcfarland@cavulus.com>
> wrote:
>
> > Hey Rayman,
> >
> > The ops group and I went through the configuration today and observed the
> > YARN containers as they were coming up. We seem to have found the root of
> > the problem, and I'm putting this out there for anybody else that's
> trying
> > to do something similar on AWS ECS:
> >
> > The ECS container instances set their hostname to the container ID on
> > startup (ie 717b6f75aaf8), and this looks like it's interfering with the
> > YARN container startup process. This *seems* to be corroborated in that
> > containers that start on the same host as their AM look to be starting
> fine
> > (ie they can locally resolve their IP address correctly), but containers
> > starting on other hosts don't seem to be. We were *not* having this
> problem
> > on Fargate, and my only guess is that, given Fargate's intended use case
> as
> > a replicated-services-in-the-cloud environment, AWS sets the hostname for
> > Fargate-bound Docker containers on launch (ie
> > ip-10-#-#-#.us-west-#.internal.local or whatever). (As a side note, we
> > probably would have stuck with Fargate and not run into this problem, but
> > Fargate instances are only allowed 10GB of disk space, and this wasn't
> > enough for YARN's VM requirements.)
> >
> > I've been fishing around for a way to get Samza to resolve the hostname
> to
> > something more publicly-available. I've thus far tried a) changing the
> > /etc/hosts file, and b) replacing the /bin/hostname binary in the
> container
> > with a static script, but neither of these options seem to have an effect
> > on Java's DNS resolution. Two further options I can think of are:
> >
> > - find some place in the Samza configuration where the hostname can be
> set
> > explicitly; or
> > - change just the right piece of information in the system so that
> > java.net.InetAddress will resolve the localhost to something other than
> > what's returned from /bin/hostname (I'm guessing it uses gethostname() on
> > Ubuntu, could be wrong).
> >
> > Anybody ideas?
> >
> > Cheers,
> > Malcolm McFarland
> > Cavulus
> >
> >
> > This correspondence is from HealthPlanCRM, LLC, d/b/a Cavulus. Any
> > unauthorized or improper disclosure, copying, distribution, or use of the
> > contents of this message is prohibited. The information contained in this
> > message is intended only for the personal and confidential use of the
> > recipient(s) named above. If you have received this message in error,
> > please notify the sender immediately and delete the original message.
> >
> > Malcolm McFarland
> > Cavulus
> >
> >
> > This correspondence is from HealthPlanCRM, LLC, d/b/a Cavulus. Any
> > unauthorized or improper disclosure, copying, distribution, or use of the
> > contents of this message is prohibited. The information contained in this
> > message is intended only for the personal and confidential use of the
> > recipient(s) named above. If you have received this message in error,
> > please notify the sender immediately and delete the original message.
> >
> >
> > On Fri, May 31, 2019 at 9:27 AM rayman preet <rayman7718@gmail.com>
> wrote:
> >
> > > Yes I think your hunch is right. Each container queries the AM over
> HTTP
> > to
> > > obtain
> > > the jobModel that it is supposed to run. The AM runs a HTTP server
> > usually
> > > on
> > > a dynamically allocated free port on the machine it's running on.
> > > So its possible that a firewall rule blocks the container when it tries
> > to
> > > reach this port
> > > on the AM's machine?
> > >
> > > --
> > > thanks
> > > rayman
> > >
> > > On Thu, May 30, 2019 at 5:30 PM Malcolm McFarland <
> > mmcfarland@cavulus.com>
> > > wrote:
> > >
> > > > Thanks for the image, appreciate you taking the effort to do that!
> I'm
> > > > still hitting this wall. The AM will launch the container, the
> > container
> > > > will go from "accepted" to "running", but there will be no output
> from
> > > the
> > > > container (I'm piping all of the Samza, org.apache, org.kafka, and
> our
> > > own
> > > > application's logging output to a Kafka topic). During these periods,
> > the
> > > > container will hang out at ~100MB/8GB memory usage and stall. There's
> > no
> > > > error output when this happens; it just kind of stops. My suspicion
> is
> > > that
> > > > our Ops group has a firewall rule up that's interfering with this,or
> > > maybe
> > > > just isn't white-listing a port correctly, and if I could identify
> > where
> > > > the application is stalling, it'd probably help to narrow down the
> > > > possibilities.
> > > >
> > > > Cheers,
> > > > Malcolm McFarland
> > > > Cavulus
> > > >
> > > >
> > > > This correspondence is from HealthPlanCRM, LLC, d/b/a Cavulus. Any
> > > > unauthorized or improper disclosure, copying, distribution, or use of
> > the
> > > > contents of this message is prohibited. The information contained in
> > this
> > > > message is intended only for the personal and confidential use of the
> > > > recipient(s) named above. If you have received this message in error,
> > > > please notify the sender immediately and delete the original message.
> > > >
> > > >
> > > > On Thu, May 30, 2019 at 1:39 PM rayman preet <rayman7718@gmail.com>
> > > wrote:
> > > >
> > > > > I uploaded the image here:
> > > > > https://www.dropbox.com/s/rv57v165ysp12c5/samza%20flow.png?dl=0
> > > > >
> > > > > Are you still running into this issue?
> > > > > Is there anything in the container's log that shows any
> > > > exceptions/errors.
> > > > >
> > > > > On Wed, May 22, 2019 at 10:15 PM Malcolm McFarland <
> > > > mmcfarland@cavulus.com
> > > > > >
> > > > > wrote:
> > > > >
> > > > > > Hey rayman,
> > > > > >
> > > > > > What it looks like is that the AM has started, the container
has
> > > > started,
> > > > > > but, ie, here will be the last messages I see in the Samza logs:
> > > > > >
> > > > > > 2019-05-23T05:10:45.048Z        INFO    Making a request for
> > ANY_HOST
> > > > > > 2019-05-23T05:10:45.057Z        INFO    Starting the container
> > > > allocator
> > > > > > thread
> > > > > > 2019-05-23T05:10:47.098Z        INFO    Received new token for
:
> > > > > > <valid_host>:8032
> > > > > > 2019-05-23T05:10:47.102Z        INFO    Container allocated
from
> RM
> > > on
> > > > > > <same_valid_host>
> > > > > > 2019-05-23T05:10:47.105Z        INFO    Container allocated
from
> RM
> > > on
> > > > > > <same_valid_host>
> > > > > >
> > > > > > At this point, it seems to stall, and no more output is produced.
> > > > > >
> > > > > > Also, I couldn't see you diagram (it's possible my company's
> email
> > > > > filters
> > > > > > attachments); can I see that on the web anywhere?
> > > > > >
> > > > > > Cheers,
> > > > > > Malcolm
> > > > > >
> > > > > > On Wed, May 22, 2019 at 4:30 PM rayman preet <
> rayman7718@gmail.com
> > >
> > > > > wrote:
> > > > > >
> > > > > > > Hi Malcolm,
> > > > > > >
> > > > > > > This figure (attached) gives an overview of the flow. Is
> > > > > > > this something you were looking for?
> > > > > > >
> > > > > > > Also, by "don't fully start up" do you mean that
> > > > > > > applications are missing some containers (but the
> > ApplicationMaster
> > > > is
> > > > > > > running)?
> > > > > > > Or the application is missing entirely.
> > > > > > >
> > > > > > > --
> > > > > > > thanks
> > > > > > > rayman
> > > > > > > [image: Samza Job Launch Sequence.png]
> > > > > > >
> > > > > > > On Tue, May 21, 2019 at 3:58 PM Malcolm McFarland <
> > > > > > mmcfarland@cavulus.com>
> > > > > > > wrote:
> > > > > > >
> > > > > > >> Hey Folks,
> > > > > > >>
> > > > > > >> I'm still trying to pin down why these applications
are
> > sometimes
> > > > not
> > > > > > >> starting. Everything looks fine in the YARN web UI
and in the
> > > > > > >> immediately available logs, but the applications don't
always
> > > fully
> > > > > > >> start up. Does anybody have a rundown about how to
trace the
> > Samza
> > > > > > >> startup process on a YARN cluster, from Accepted status,
to
> > > > > > >> localization, to the application master startup, to
the actual
> > > > > > >> application's startup?
> > > > > > >>
> > > > > > >> Cheers,
> > > > > > >> Malcolm
> > > > > > >>
> > > > > > >> --
> > > > > > >> Malcolm McFarland
> > > > > > >> Cavulus
> > > > > > >>
> > > > > > >>
> > > > > > >> This correspondence is from HealthPlanCRM, LLC, d/b/a
Cavulus.
> > Any
> > > > > > >> unauthorized or improper disclosure, copying, distribution,
or
> > use
> > > > of
> > > > > > >> the contents of this message is prohibited. The information
> > > > contained
> > > > > > >> in this message is intended only for the personal and
> > confidential
> > > > use
> > > > > > >> of the recipient(s) named above. If you have received
this
> > message
> > > > in
> > > > > > >> error, please notify the sender immediately and delete
the
> > > original
> > > > > > >> message.
> > > > > > >>
> > > > > > >
> > > > > > >
> > > > > > > --
> > > > > > > thanks
> > > > > > > rayman
> > > > > > >
> > > > > >
> > > > > >
> > > > > > --
> > > > > > Malcolm McFarland
> > > > > > Cavulus
> > > > > > 1-800-760-6915
> > > > > > mmcfarland@cavulus.com
> > > > > >
> > > > > >
> > > > > > This correspondence is from HealthPlanCRM, LLC, d/b/a Cavulus.
> Any
> > > > > > unauthorized or improper disclosure, copying, distribution,
or
> use
> > of
> > > > the
> > > > > > contents of this message is prohibited. The information contained
> > in
> > > > this
> > > > > > message is intended only for the personal and confidential use
of
> > the
> > > > > > recipient(s) named above. If you have received this message
in
> > error,
> > > > > > please notify the sender immediately and delete the original
> > message.
> > > > > >
> > > > >
> > > > >
> > > > > --
> > > > > thanks
> > > > > rayman
> > > > >
> > > >
> > >
> > >
> > > --
> > > thanks
> > > rayman
> > >
> >
>
>
> --
> thanks
> rayman
>

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