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From "Matthew Hager [W2O Digital]" <>
Subject Re: Proposing Changes to the StreamsProvider interface and StreamsProviderTask
Date Thu, 12 Jun 2014 14:59:43 GMT
:+1: right now they have no way to talk to each other. Provider doesn't know when he is going
to be polled again and the builder implementation has no idea if the provider is done providing.

Sent from my iPhone

> On Jun 12, 2014, at 8:51 AM, Matt Franklin <> wrote:
> Do we have consensus on next steps?  From what I can see, everyone agrees
> that the addition of an isRunning method to the provider makes sense.  I
> will create a ticket and commit that change; but, I encourage others to
> continue discussion on the next steps for improvement.
> On Thu, May 15, 2014 at 11:53 AM, Robert Douglas [W2O Digital] <
>> wrote:
>> Hi all,
>> After working with the Streams project a bit, I have noticed some of the
>> same issues that Matt and Ryan have brought up. I think that Matt's idea
>> to implement two interfaces (Producer, Listener) would make a great
>> addition to the project. Not only would it increase efficiency but it
>> would also, in my opinion, make the streams themselves easier to construct
>> and understand.
>> -- Robert
>> On 5/7/14, 1:41 PM, "Matthew Hager [W2O Digital]" <>
>> wrote:
>>> Good Day!
>>> I would like to throw in my two pents in on this if it pleases the
>>> community.
>>> Here are my thoughts based on implementations that I have written with
>>> streams to ensure timely, high yield execution. Personally, I had to
>>> override much of the LocalStreamsBuilder to fit my use cases for many of
>>> the problems described below, except the opposite of which. I have a
>>> modality of a 'finite' stream which execution is hindered when being
>>> 'polled' in the manner that it is. This is further complicated by the
>>> excessive waiting caused by the current 'shutdown' the exists.
>>> There are essentially two major use-cases, that I can see, that are likely
>>> to take place. The first is a perpetual stream, that is technically never
>>> satisfied. The second, is the case of a finite stream (HDFS reader, S3
>>> reader, pulling a user's time-line, etc...) that has a definitive start
>>> and end. To solve these two models of execution here are my thoughts.
>>> StreamsResultSet - I actually found this to be quite useful paradigm. A
>>> queue prevents a buffer overflow, an iterator makes it fun and easy to
>>> read (I love iterators), and it is simple and succinct. I do, however,
>>> feel it is best expressed as an interface instead of a class. Personally I
>>> had to override almost every function to fit the concept of a 'finite'
>>> stream. Without an expensive tear-down cost. The thing missing from this,
>>> as an interface, would be the notion of "isRunning" which could easily
>>> satisfy both of the aforementioned modalities. (As Ryan suggested) I
>>> actually have a reference implementation of this for finite streams if
>>> anyone would like to see it or use it.
>>> Event Driven - I concur with Matt 100% on this. As currently implemented,
>>> LocalStreamsBuilder is exceedingly inefficient from a memory perspective
>>> and time execution perspective. To me, it seems, that we could almost
>>> abstract out 2 common interfaces to make this happen.
>>>      * Listener { receive(StreamsDatum); }
>>>      * Producer { push(StreamsDatum); registerListener(Listener); }
>>> Where the following implementations would place:
>>>      * Reader implements Producer
>>>      * Processor implements Producer, Listener
>>>      * Writer implements Listener
>>> In the reference implementations, you can still have queues that are in
>>> place that could actually function as meaningful indicators of system
>>> performance and status. IE: the queue functions as, well, an actually
>>> queue, and processes are much more asynchronous than they currently are
>>> now. Then, LocalStreamsBuilder strings all the guys up together in their
>>> nice little workflows and the events just shoot the little Datums down
>>> their paths until they wind up wherever they are supposed to go as quickly
>>> as possible.
>>> Pardon the long response, I tend to be wordy, great discussion and thanks
>>> to everyone for indulging my thoughts!
>>> Cheers!
>>> Smashew (Matthew Hager)
>>> Matthew Hager
>>> Director - Data Sciences Software
>>> W2O Digital
>>> 3000
>>> E Cesar Chavez St., Suite 300, Austin, Texas 78702
>>> direct 512.551.0891 | cell 512.949.9603
>>> twitter iSmashew
>>> <
>>> 7f3HFLf6QrEzxPUV6XVKa5mO9-Q1hxeG4ycFWvOVIMDl2h6kZfVsSCUwMWUO_R-svhuKPRXBQS
>>> hPD8ETv7czKmKDp55mWavaxVZicHs3jq9JcTvAXTLuZXTKrKr01PciDfUYLAGaXgDVz3q7CiYv
>>> CT61ssesbNgGShfSxNxeG4ycFWvOUaFefWHjFgISgStoZGSS9_M04SyyYeodwLQzh05ERmHik2
>>> 9Ew4yuM8_gQgjGq89A_d40NefWHgbhGpAxYjh1a4_yXJLd46Mgd40NefWHgbhGpAxYgjJ2FIsY
>>> rVGx8qNRO> | linkedin Matthew Hager
>>> <
>>> xRQTDzqdQhMVYsztYT52Hp4_q0EMDl2h6kZfVsSojGx8zauDYKrjsgotspvW_efELnpWZOWr8V
>>> PAkrLzChTbnjIyyHt5fBgY-F6lK1FJcSCrLOtXTLuZXTdTdw0zVga-xa7bUJ6HIz_MPbP1ai1P
>>> NEVovpd78USxVAL7VJNwn73D2YkaJAjZEsojGx8zauDYK2Gjz-GQWkbdAdDmfqJJyvY01dEEL3
>>> C3obZ8Qg1qdlGQB0yq818DI2fQd44WCy2pfPh0cjz-GQ2QqCp8v4QgixfUKXrPh1I43h0cjz-G
>>> Q2QqCp8v44XgGr7f6_558nD-1>
>>>> On 5/6/14, 10:58 AM, "Steve Blackmon" <> wrote:
>>>> On Tue, May 6, 2014 at 8:24 AM, Matt Franklin <>
>>>> wrote:
>>>>> On Mon, May 5, 2014 at 1:15 PM, Steve Blackmon <>
>>>>> wrote:
>>>>>> What I meant to say re #1 below is that batch-level metadata could
>>>>>> useful for modules downstream of the StreamsProvider /
>>>>>> StreamsPersistReader, and the StreamsResultSet gives us a class to
>>>>>> which we can add new metadata in core as the project evolves, or
>>>>>> supplement on a per-module or per-implementation basis via
>>>>>> subclassing.  Within a provider there's no need to modify or extend
>>>>>> StreamsResultSet to maintain and utilize state from a third-party
>>>>> I agree that in batch mode, metadata might be important.  In
>>>>> conversations
>>>>> with other people, I think what might be missing is a completely
>>>>> reactive,
>>>>> event-driven mode where a provider pushes to the rest of the stream
>>>>> rather
>>>>> than gets polled.
>>>> That would certainly be nice, but I see it as primarily a run-time
>>>> concern.  We should add additional methods to the core interfaces if
>>>> we need them to make a push run-time (backed by camel, nsq, activemq,
>>>> 0mq, etc...) work, but let's stay vigilant to keep the number of
>>>> methods on those interfaces to a minimum so we don't end up with a)
>>>> classes that do a lot of stuff in core b) an effective partition
>>>> between methods necessary for perpetual and batch modes c) lots of
>>>> modules that implement just one or the other.  Modules that don't
>>>> implement all run-modes is already a problem.
>>>> So who wants to volunteer to write a push-based run-time module?
>>>>>> I think I would support making StreamsResultSet an interface rather
>>>>>> than a class.
>>>>> +1 on interface
>>>>>> Steve Blackmon
>>>>>> On Mon, May 5, 2014 at 12:07 PM, Steve Blackmon <>
>>>>>> wrote:
>>>>>>> Comments on this in-line below.
>>>>>>> On Thu, May 1, 2014 at 4:38 PM, Ryan Ebanks <>
>>>>>> wrote:
>>>>>>>> The use and implementations of the StreamsProviders seems
to have
>>>>>> drifted
>>>>>>>> away from what it was originally designed for.  I recommend
that we
>>>>>> change
>>>>>>>> the StreamsProvider interface and StreamsProvider task to
>>>>>> the
>>>>>>>> current usage patterns and to be more efficient.
>>>>>>>> Current Problems:
>>>>>>>> 1.) newPerpetualStream in LocalStream builder is not perpetual.
>>>>>> The
>>>>>>>> StreamProvider task will shut down after a certain amount
of empty
>>>>>> returns
>>>>>>>> from the provider.  A perpetual stream implies that it will
run in
>>>>>>>> perpetuity.  If I open a Twitter Gardenhose that is returning
>>>>>> tweets
>>>>>> with
>>>>>>>> obscure key words, I don't want my stream shutting down if
it is
>>>>>> just
>>>>>> quiet
>>>>>>>> for a few time periods.
>>>>>>>> 2.) StreamsProviderTasks assumes that a single read*, will
>>>>>> all
>>>>>> the
>>>>>>>> data for that request.  This means that if I do a readRange
for a
>>>>>> year,
>>>>>> the
>>>>>>>> provider has to hold all of that data in memory and return
it as
>>>>>> one
>>>>>>>> StreamsResultSet.  I believe the readPerpetual was designed
to get
>>>>>> around
>>>>>>>> this problem.
>>>>>>>> Proposed Fixes/Changes:
>>>>>>>> Fix 1.) Remove the StreamsResultSet.  No implementations
in the
>>>>>> project
>>>>>>>> currently use it for anything other than a wrapper around
a Queue
>>>>>> that
>>>>>> is
>>>>>>>> then iterated over.  StreamsProvider will now return a
>>>>>> Queue<StreamsDatum>
>>>>>>>> instead of a StreamsResultSet.  This will allow providers
to queue
>>>>>> data
>>>>>> as
>>>>>>>> they receive it, and the StreamsProviderTask can pop them
off as
>>>>>> soon as
>>>>>>>> they are available.  It will help fix problem #2, as well
as help
>>>>>> to
>>>>>> lower
>>>>>>>> memory usage.
>>>>>>> I'm not convinced this is a good idea.  StreamsResultSet is a
>>>>>>> abstraction even if no modules are using it as more than a wrapper
>>>>>> for
>>>>>>> Queue at the moment.  For example read* in a provider or
>>>>>> persistReader
>>>>>>> could return batch-level (as opposed to datum-level) metadata
>>>>>> the
>>>>>>> underlying API which would be useful state for the provider.
>>>>>>> Switching to Queue would eliminate our ability to add those
>>>>>>> capabilities at the core level or at the module level.
>>>>>>>> Fix 2.) Add a method, public boolean isRunning(), to the
>>>>>> StreamsProvider
>>>>>>>> interface.  The StreamsProviderTask can call this function
to see
>>>>>> if the
>>>>>>>> provider is still operating. This will help fix problems
#1 and #2.
>>>>>> This
>>>>>>>> will allow the provider to run mulitthreaded, queue data
as it's
>>>>>> available,
>>>>>>>> and notify the task when it's done so that it can be closed
>>>>>> properly.
>>>>>>>> It will also allow the stream to be run in perpetuity as
>>>>>> StreamTask
>>>>>>>> won't shut down providers that have not been producing data
for a
>>>>>> while.
>>>>>>> I think this is a good idea.  +1
>>>>>>>> Right now the StreamsProvider and StreamsProviderTask seem
to be
>>>>>> full of
>>>>>>>> short term fixes that need to be redesigned into long term
>>>>>> solutions.
>>>>>> With
>>>>>>>> enough positive feedback, I will create Jira tasks, a feature
>>>>>> branch,
>>>>>> and
>>>>>>>> begin work.
>>>>>>>> Sincerely,
>>>>>>>> Ryan Ebanks
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