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From David McLaughlin <da...@dmclaughlin.com>
Subject Re: JobConfig diff API
Date Fri, 02 Oct 2015 20:29:47 GMT
I'd like to propose an alternative - that we start off by having an API
endpoint which simply returns the JobUpdateInstructions that describes the
changes that would happen if a given JobUpdateRequest was applied.

There is a lot of value in having clients ask the scheduler to tell them
what is going to happen rather than try and duplicate that diff algorithm
in both places. Of course this does not solve the "pretty" diff command
when trying to *display* the differences, but it does remove a lot of the
work in implementing the diff command and I think for the different types
of clients (UI/CLI/etc.) displaying the diffs is going to be a much bigger
problem anyway.

In the future if the scheduler does calculate and return some
representation of the diff, I'd argue that it should be stored in
JobUpdateInstructions anyway, so we can always add that functionality later
and keep the APIs the same.

Thanks,
David


On Wed, Sep 16, 2015 at 10:23 AM, Bill Farner <wfarner@apache.org> wrote:

> I think it's fine to provide an 'enhanced' experience when the format is
> JSON, but i don't think we should force that.
>
> On Wed, Sep 16, 2015 at 10:22 AM, Maxim Khutornenko <maxim@apache.org>
> wrote:
>
> > The benefit of assuming a certain format is the richer experience we
> > can give to our users. The *blob* may be too large to make any sense
> > of it during diffing. I don't propose to enforce any schema though,
> > that would be too restrictive. I do however believe assuming JSON
> > format would be an acceptable tradeoff.
> >
> > Alternatively, we may allow non-JSON (e.g. binary) executor data blobs
> > and disabling JSON diffs for any executor types that don't follow the
> > guidance. This will result in a degraded user experience but may be
> > the middle ground here. Thoughts?
> >
> > On Tue, Sep 15, 2015 at 11:43 AM,  <meghdoot_b@yahoo.com.invalid> wrote:
> > > Isn't this data supposed to be any blob that transparently passes in to
> > the executor through mesos data blob. Why would we want to impose any
> sort
> > of format? It could be a binary blob. Executor writers should be able to
> > move between different schedulers/frameworks without any rework ideally.
> > This field seems like more like garbage in and garbage out and only
> > understood by end client and the executor. Scheduler may stay out of it.
> > > If you compute hash and indicate same or different data between 2 job
> > update diff, that may be reasonable.
> > >
> > > My 2 cents.
> > >
> > > Thx
> > >
> > > Sent from my iPhone
> > >
> > >> On Sep 15, 2015, at 11:01 AM, Zameer Manji <zmanji@apache.org> wrote:
> > >>
> > >> I'm a proponent of firming up our executor <-> scheduler contract.
> > Since we
> > >> are going to get multiple executor support soon I think it would be
> > nice if
> > >> we said that ExecutorConfig.data was JSON.
> > >>
> > >> On Tue, Sep 15, 2015 at 10:47 AM, Maxim Khutornenko <maxim@apache.org
> >
> > >> wrote:
> > >>
> > >>> | I hope this doesn't mean we would be returning a textual
> > >>> representation of a diff
> > >>>
> > >>> If we can make an assumption that executor data is always JSON, we
> can
> > >>> deliver a much more specific answer by applying JSON diff tools.
> > >>> Something like:
> > >>>
> > >>> - "environment": "prod"
> > >>> + "environment": "test"
> > >>>
> > >>> Otherwise, we would have to output the entire ExecutorConfig.data
> blob
> > >>> content for both left and right sides and let users figure out the
> > >>> problem. I don't think that's acceptable.
> > >>>
> > >>> Does it make sense? Any suggestions on the output format of the diff?
> > >>> I think it should be structured but at the same time we have to get
> > >>> down to text level at some point to report concrete discrepancies.
> > >>>
> > >>>> On Mon, Sep 14, 2015 at 8:58 PM, Bill Farner <wfarner@apache.org>
> > wrote:
> > >>>> The 'blob'-iness of ExecutorConfig is intentional so that we can
> > support
> > >>>> alternative executors.  I'd hate for that to go away.
> > >>>>
> > >>>>> On Mon, Sep 14, 2015 at 8:56 PM, Jake Farrell <jfarrell@apache.org
> >
> > >>>> wrote:
> > >>>>
> > >>>>> This is one of the hoops encountered when using the Thrift
api
> > directly
> > >>> and
> > >>>>> not using the client, I'd love to see ExecutorConfig.data move
to a
> > >>> thrift
> > >>>>> object and not be a string blob
> > >>>>>
> > >>>>> -Jake
> > >>>>>
> > >>>>> On Mon, Sep 14, 2015 at 9:28 PM, Bill Farner <wfarner@apache.org>
> > >>> wrote:
> > >>>>>
> > >>>>>> I like the idea of adding this API, but i don't see why
it
> requires
> > >>> us to
> > >>>>>> make assumptions about ExecutorConfig.data.  I hope this
doesn't
> > mean
> > >>> we
> > >>>>>> would be returning a textual representation of a diff.
 Can you
> > >>> elaborate
> > >>>>>> on that?
> > >>>>>>
> > >>>>>> On Mon, Sep 14, 2015 at 4:14 PM, Maxim Khutornenko <
> > maxim@apache.org>
> > >>>>>> wrote:
> > >>>>>>
> > >>>>>>> Problem:
> > >>>>>>> We currently don't have a good user experience around
"aurora job
> > >>>>>>> diff" command. The task configs are dumped as "prettified"
JSON
> > >>>>>>> strings and diffed with the system diff tool. Anyone
who tried to
> > >>> use
> > >>>>>>> it knows it can be very hard to read especially when
it comes to
> > >>>>>>> executor data deltas. Also, the implementation is done
completely
> > >>>>>>> within the Aurora client making it hard to reuse this
feature by
> > >>> other
> > >>>>>>> clients (e.g.: an external deploy coordination tool).
> > >>>>>>>
> > >>>>>>> Proposal:
> > >>>>>>> Move the diff logic to the scheduler and expose it
via a new
> > >>>>>>> jobConfigDiff thrift API.
> > >>>>>>>
> > >>>>>>> Benefits:
> > >>>>>>> - Client will no longer have the custom non-reusable
logic moving
> > us
> > >>>>>>> closer towards a "thin client" goal.
> > >>>>>>> - The new RPC can be fully used by any existing or
new API
> clients.
> > >>>>>>> - The diff output will be improved via leveraging third
party
> POJO
> > >>>>>>> and/or JSON diff libraries [1,2,3, etc.].
> > >>>>>>> - The server updater can be partially/fully unified
with the new
> > >>> diff
> > >>>>>>> logic further improving the overall DRY-ness.
> > >>>>>>>
> > >>>>>>> Concerns:
> > >>>>>>> - The executor data is currently treated as an opaque
string blob
> > on
> > >>>>>>> the scheduler side. In reality, it's almost guaranteed
to be
> JSON.
> > >>> In
> > >>>>>>> order to deliver the best UX, the scheduler would have
to start
> > >>>>>>> requiring ExecutorConfig.data to be a valid JSON.
> > >>>>>>>
> > >>>>>>> Any other concerns/objections/comments? I would like
to formalize
> > >>> the
> > >>>>>>> proposal be EOW if we reach consensus quickly.
> > >>>>>>>
> > >>>>>>> Thanks,
> > >>>>>>> Maxim
> > >>>>>>>
> > >>>>>>> [1] -
> > >>>
> >
> http://java-object-diff.readthedocs.org/en/latest/getting-started/#getting-started
> > >>>>>>> [2] - http://javers.org/documentation/diff-examples/
> > >>>>>>> [3] - https://github.com/skyscreamer/JSONassert
> > >>>
> > >>> --
> > >>> Zameer Manji
> > >>>
> > >>>
> >
>

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