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From xinyu liu <xinyuliu...@gmail.com>
Subject Re: [DISCUSS] SEP-2: ApplicationRunner Design
Date Fri, 28 Apr 2017 04:11:53 GMT
Let me try to capture the updated requirements:

1. Set up input streams outside StreamGraph, and treat graph building as a
library (*Fluent, Beam*).

2. Improve ease of use for ApplicationRunner to avoid complex
configurations such as zkCoordinator, zkCoordinationService. (*Standalone*).
Provide some programmatic way to tweak them in the API.

3. Clean up ApplicationRunner into a single interface (*Fluent*). We can
have one or more implementations but it's hidden from the users.

4. Separate StreamGraph from runtime environment so it can be
serialized (*Beam,
Yarn*)

5. Better life cycle management of application, parity with StreamProcessor
(*Standalone, Beam*). Stats should include exception in case of failure
(tracked in SAMZA-1246).

6. Support injecting user-defined objects into ApplicationRunner.

Prateek and I iterate on the ApplilcationRunner API based on these
requirements. To support #1, we can set up input streams on the runner
level, which returns the MessageStream and allows graph building
afterwards. The code looks like below:

  ApplicationRunner runner = ApplicationRunner.local();
  runner.input(streamSpec)
            .map(..)
            .window(...)
  runner.run();

StreamSpec is the building block for setting up streams here. It can be set
up in different ways:

  - Direct creation of stream spec, like runner.input(new StreamSpec(id,
system, stream))
  - Load from streamId from env or config, like
runner.input(runner.env().getStreamSpec(id))
  - Canned Spec which generates the StreamSpec with id, system and stream
to minimize the configuration. For example, CollectionSpec.create(new
ArrayList[]{1,2,3,4}), which will auto generate the system and stream in
the spec.

To support #2, we need to be able to set up StreamSpec-related objects and
factories programmatically in env. Suppose we have the following before
runner.input(...):

  runner.setup(env /* a writable interface of env*/ -> {
    env.setStreamSpec(streamId, streamSpec);
    env.setSystem(systemName, systemFactory);
  })

runner.setup(->) also provides setup for stores and other runtime stuff
needed for the execution. The setup should be able to serialized to config.
For #6, I haven't figured out a good way to inject user-defined objects
here yet.

With this API, we should be able to also support #4. For remote
runner.run(), the operator user classes/lamdas in the StreamGraph need to
be serialized. As today, the existing option is to serialize to a stream,
either the coordinator stream or the pipeline control stream, which will
have the size limit per message. Do you see RPC as an option?

For this version of API, seems we don't need the StreamApplication wrapper
as well as exposing the StreamGraph. Do you think we are on the right path?

Thanks,
Xinyu


On Thu, Apr 27, 2017 at 6:09 AM, Chris Pettitt <
cpettitt@linkedin.com.invalid> wrote:

> That should have been:
>
> For #1, Beam doesn't have a hard requirement...
>
> On Thu, Apr 27, 2017 at 9:07 AM, Chris Pettitt <cpettitt@linkedin.com>
> wrote:
>
> > For #1, I doesn't have a hard requirement for any change from Samza. A
> > very nice to have would be to allow the input systems to be set up at the
> > same time as the rest of the StreamGraph. An even nicer to have would be
> to
> > do away with the callback based approach and treat graph building as a
> > library, a la Beam and Flink.
> >
> > For the moment I've worked around the two pass requirement (once for
> > config, once for StreamGraph) by introducing an IR layer between Beam and
> > the Samza Fluent translation. The IR layer is convenient independent of
> > this problem because it makes it easier to switch between the Fluent and
> > low-level APIs.
> >
> >
> > For #4, if we had parity with StreamProcessor for lifecycle we'd be in
> > great shape. One additional issue with the status call that I may not
> have
> > mentioned is that it provides you no way to get at the cause of failure.
> > The StreamProcessor API does allow this via the callback.
> >
> >
> > Re. #2 and #3, I'm a big fan of getting rid of the extra configuration
> > indirection you currently have to jump through (this is also related to
> > system consumer configuration from #1. It makes it much easier to
> discover
> > what the configurable parameters are too, if we provide some programmatic
> > way to tweak them in the API - which can turn into config under the hood.
> >
> > On Wed, Apr 26, 2017 at 9:20 PM, xinyu liu <xinyuliu.us@gmail.com>
> wrote:
> >
> >> Let me give a shot to summarize the requirements for ApplicationRunner
> we
> >> have discussed so far:
> >>
> >> - Support environment for passing in user-defined objects (streams
> >> potentially) into ApplicationRunner (*Beam*)
> >>
> >> - Improve ease of use for ApplicationRunner to avoid complex
> >> configurations
> >> such as zkCoordinator, zkCoordinationService. (*Standalone*)
> >>
> >> - Clean up ApplicationRunner into a single interface (*Fluent*). We can
> >> have one or more implementations but it's hidden from the users.
> >>
> >> - Separate StreamGraph from environment so it can be serializable
> (*Beam,
> >> Yarn*)
> >>
> >> - Better life cycle management of application, including
> >> start/stop/stats (*Standalone,
> >> Beam*)
> >>
> >>
> >> One way to address 2 and 3 is to provide pre-packaged runner using
> static
> >> factory methods, and the return type will be the ApplicationRunner
> >> interface. So we can have:
> >>
> >>   ApplicationRunner runner = ApplicationRunner.zk() /
> >> ApplicationRunner.local()
> >> / ApplicationRunner.remote() / ApplicationRunner.test().
> >>
> >> Internally we will package the right configs and run-time environment
> with
> >> the runner. For example, ApplicationRunner.zk() will define all the
> >> configs
> >> needed for zk coordination.
> >>
> >> To support 1 and 4, can we pass in a lambda function in the runner, and
> >> then we can run the stream graph? Like the following:
> >>
> >>   ApplicationRunner.zk().env(config -> environment).run(streamGraph);
> >>
> >> Then we need a way to pass the environment into the StreamGraph. This
> can
> >> be done by either adding an extra parameter to each operator, or have a
> >> getEnv() function in the MessageStream, which seems to be pretty hacky.
> >>
> >> What do you think?
> >>
> >> Thanks,
> >> Xinyu
> >>
> >>
> >>
> >>
> >>
> >> On Sun, Apr 23, 2017 at 11:01 PM, Prateek Maheshwari <
> >> pmaheshwari@linkedin.com.invalid> wrote:
> >>
> >> > Thanks for putting this together Yi!
> >> >
> >> > I agree with Jake, it does seem like there are a few too many moving
> >> parts
> >> > here. That said, the problem being solved is pretty broad, so let me
> >> try to
> >> > summarize my current understanding of the requirements. Please correct
> >> me
> >> > if I'm wrong or missing something.
> >> >
> >> > ApplicationRunner and JobRunner first, ignoring test environment for
> the
> >> > moment.
> >> > ApplicationRunner:
> >> > 1. Create execution plan: Same in Standalone and Yarn
> >> > 2. Create intermediate streams: Same logic but different leader
> election
> >> > (ZK-based or pre-configured in standalone, AM in Yarn).
> >> > 3. Run jobs: In JVM in standalone. Submit to the cluster in Yarn.
> >> >
> >> > JobRunner:
> >> > 1. Run the StreamProcessors: Same process in Standalone & Test. Remote
> >> host
> >> > in Yarn.
> >> >
> >> > To get a single ApplicationRunner implementation, like Jake suggested,
> >> we
> >> > need to make leader election and JobRunner implementation pluggable.
> >> > There's still the question of whether ApplicationRunner#run API should
> >> be
> >> > blocking or non-blocking. It has to be non-blocking in YARN. We want
> it
> >> to
> >> > be blocking in standalone, but seems like the main reason is ease of
> use
> >> > when launched from main(). I'd prefer making it consitently
> non-blocking
> >> > instead, esp. since in embedded standalone mode (where the processor
> is
> >> > running in another container) a blocking API would not be
> user-friendly
> >> > either. If not, we can add both run and runBlocking.
> >> >
> >> > Coming to RuntimeEnvironment, which is the least clear to me so far:
> >> > 1. I don't think RuntimeEnvironment should be responsible for
> providing
> >> > StreamSpecs for streamIds - they can be obtained with a config/util
> >> class.
> >> > The StreamProcessor should only know about logical streamIds and the
> >> > streamId <-> actual stream mapping should happen within the
> >> > SystemProducer/Consumer/Admins provided by the RuntimeEnvironment.
> >> > 2. There's also other components that the user might be interested in
> >> > providing implementations of in embedded Standalone mode (i.e., not
> >> just in
> >> > tests) - MetricsRegistry and JMXServer come to mind.
> >> > 3. Most importantly, it's not clear to me who creates and manages the
> >> > RuntimeEnvironment. It seems like it should be the ApplicationRunner
> or
> >> the
> >> > user because of (2) above and because StreamManager also needs access
> to
> >> > SystemAdmins for creating intermediate streams which users might want
> to
> >> > mock. But it also needs to be passed down to the StreamProcessor - how
> >> > would this work on Yarn?
> >> >
> >> > I think we should figure out how to integrate RuntimeEnvironment with
> >> > ApplicationRunner before we can make a call on one vs. multiple
> >> > ApplicationRunner implementations. If we do keep
> LocalApplicationRunner
> >> and
> >> > RemoteApplication (and TestApplicationRunner) separate, agree with
> Jake
> >> > that we should remove the JobRunners and roll them up into the
> >> respective
> >> > ApplicationRunners.
> >> >
> >> > - Prateek
> >> >
> >> > On Thu, Apr 20, 2017 at 10:06 AM, Jacob Maes <jacob.maes@gmail.com>
> >> wrote:
> >> >
> >> > > Thanks for the SEP!
> >> > >
> >> > > +1 on introducing these new components
> >> > > -1 on the current definition of their roles (see Design feedback
> >> below)
> >> > >
> >> > > *Design*
> >> > >
> >> > >    - If LocalJobRunner and RemoteJobRunner handle the different
> >> methods
> >> > of
> >> > >    launching a Job, what additional value do the different types of
> >> > >    ApplicationRunner and RuntimeEnvironment provide? It seems like
a
> >> red
> >> > > flag
> >> > >    that all 3 would need to change from environment to environment.
> It
> >> > >    indicates that they don't have proper modularity. The
> >> > > call-sequence-figures
> >> > >    support this; LocalApplicationRunner and RemoteApplicationRunner
> >> make
> >> > > the
> >> > >    same calls and the diagram only varies after jobRunner.start()
> >> > >    - As far as I can tell, the only difference between Local and
> >> Remote
> >> > >    ApplicationRunner is that one is blocking and the other is
> >> > > non-blocking. If
> >> > >    that's all they're for then either the names should be changed
to
> >> > > reflect
> >> > >    this, or they should be combined into one ApplicationRunner and
> >> just
> >> > > expose
> >> > >    separate methods for run() and runBlocking()
> >> > >    - There isn't much detail on why the main() methods for
> >> Local/Remote
> >> > >    have such different implementations, how they receive the
> >> Application
> >> > >    (direct vs config), and concretely how the deployment scripts,
if
> >> any,
> >> > >    should interact with them.
> >> > >
> >> > >
> >> > > *Style*
> >> > >
> >> > >    - nit: None of the 11 uses of the word "actual" in the doc are
> >> > > *actually*
> >> > >    needed. :-)
> >> > >    - nit: Colors of the runtime blocks in the diagrams are
> >> unconventional
> >> > >    and a little distracting. Reminds me of nai won bao. Now I'm
> >> hungry.
> >> > :-)
> >> > >    - Prefer the name "ExecutionEnvironment" over
> "RuntimeEnvironment".
> >> > The
> >> > >    term "execution environment" is used
> >> > >    - The code comparisons for the ApplicationRunners are not
> >> > apples-apples.
> >> > >    The local runner example is an application that USES the local
> >> runner.
> >> > > The
> >> > >    remote runner example is the just the runner code itself. So,
> it's
> >> not
> >> > >    readily apparent that we're comparing the main() methods and not
> >> the
> >> > >    application itself.
> >> > >
> >> > >
> >> > > On Mon, Apr 17, 2017 at 5:02 PM, Yi Pan <nickpan47@gmail.com>
> wrote:
> >> > >
> >> > > > Made some updates to clarify the role and functions of
> >> > RuntimeEnvironment
> >> > > > in SEP-2.
> >> > > >
> >> > > > On Fri, Apr 14, 2017 at 9:30 AM, Yi Pan <nickpan47@gmail.com>
> >> wrote:
> >> > > >
> >> > > > > Hi, everyone,
> >> > > > >
> >> > > > > In light of new features such as fluent API and standalone
that
> >> > > introduce
> >> > > > > new deployment / application launch models in Samza, I created
a
> >> new
> >> > > > SEP-2
> >> > > > > to address the new use cases. SEP-2 link: https://cwiki.apache.
> >> > > > > org/confluence/display/SAMZA/SEP-2%3A+ApplicationRunner+Design
> >> > > > >
> >> > > > > Please take a look and give feedbacks!
> >> > > > >
> >> > > > > Thanks!
> >> > > > >
> >> > > > > -Yi
> >> > > > >
> >> > > >
> >> > >
> >> >
> >>
> >
> >
>

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