[LRUG] Event Bus in ruby

Stephen Best bestie at gmail.com
Thu Aug 21 10:17:33 PDT 2014 

Klaus - Thanks so much for sharing your code, far too often these
discussions revolve around closed source applications.

I feel compelled to also share some code so the following is an example
from one of the GDS applications that I've been working on. While the
example is not pub/sub (though it could trivially be refactored that way)
it uses a simple observer implementation and demonstrates similar
decoupling goals. The biggest win for us is that this design has enabled us
to make real "open / closed" changes where we can add new functionality
without changing any existing objects.

https://github.com/alphagov/specialist-publisher/blob/73252328a1585e7a4018f5ab9888a31ae5fccc34/app/services/publish_document_service.rb


Bestie.

theaudaciouscodeexperiment.com
github.com/bestie
@thebestie


On 21 August 2014 11:49, Klaus Hebsgaard <klaus at hebsgaard.dk> wrote:

> If its of any interest to anyone this is what I have done with eventbus in
> Be My Eyes so far
> https://github.com/bemyeyes/bemyeyes-server/tree/feature/eventbus
>
> Med Venlig hilsen / Best regards
>
> Klaus Hebsgaard
>
> Website: http://www.hebsgaard.dk
> Blog: *http://blog.khebbie.dk <http://blog.khebbie.dk>*
> LinkedIIn: http://www.linkedin.com/in/klaushebsgaard
> Github: https://github.com/khebbie
>
>
> On Wed, Aug 20, 2014 at 2:04 PM, Klaus Hebsgaard <klaus at hebsgaard.dk>
> wrote:
>
>> Yes, EventBus it the one I ended up with.
>> Seems pretty solid, and since Paul Robinson gave a thumbs up for the
>> author that makes me trust it more.
>>
>> The only problem I have is that EventBus is meant to be used in a static
>> fasion which makes unit testing a bit harder, but not impossible...
>>
>> Med Venlig hilsen / Best regards
>>
>> Klaus Hebsgaard
>>
>> Website: http://www.hebsgaard.dk
>> Blog: *http://blog.khebbie.dk <http://blog.khebbie.dk>*
>> LinkedIIn: http://www.linkedin.com/in/klaushebsgaard
>> Github: https://github.com/khebbie
>>
>>
>> On Wed, Aug 20, 2014 at 1:38 PM, Stephen Best <bestie at gmail.com> wrote:
>>
>>> Klaus I think you answered your own question with "implement a simple
>>> observer pattern". Synchronous pub/sub is trivial to implement with plain
>>> old Ruby objects with this approach offering the best in terms of
>>> decoupling.
>>>
>>> Applied correctly it should be very easy to later swap out your event
>>> consumers for objects that put jobs onto asynchronous queues.
>>>
>>> Wisper seems to encourage users to have domain or ActiveRecord objects
>>> emit events which I find a bit distasteful.
>>>
>>> EventBus seems like a much better option if you'd rather use a library.
>>>
>>> Bestie.
>>>
>>> theaudaciouscodeexperiment.com
>>> github.com/bestie
>>> @thebestie
>>>
>>>
>>> On 20 August 2014 12:15, Klaus Hebsgaard <klaus at hebsgaard.dk> wrote:
>>>
>>>> Thank you everyone who gave suggestions
>>>>
>>>> Med Venlig hilsen / Best regards
>>>>
>>>> Klaus Hebsgaard
>>>>
>>>> Website: http://www.hebsgaard.dk
>>>> Blog: *http://blog.khebbie.dk <http://blog.khebbie.dk>*
>>>> LinkedIIn: http://www.linkedin.com/in/klaushebsgaard
>>>> Github: https://github.com/khebbie
>>>>
>>>>
>>>> On Wed, Aug 20, 2014 at 12:41 PM, James Pike <lrug at chilon.net> wrote:
>>>>
>>>>> The awkward thing about Redis is you only get a single "watch" per TCP
>>>>> connection, with the exception of pub sub (which puts your connection
>>>>> into "subscriber mode" and limits it to only pub/sub operations). If
>>>>> you
>>>>> only want to stick to pubsub then it's cool, but then if you are
>>>>> tempted
>>>>> by other things like queues and hashes and operations to watch them,
>>>>> then you have to start having to spawn multiple TCP connections for
>>>>> each
>>>>> watch operation, and then writing connection pools etc. That makes me
>>>>> sad.
>>>>>
>>>>> RabbitMQ is nice in that you can consume all its goods with a single
>>>>> TCP
>>>>> connection.
>>>>>
>>>>> Cheers, James
>>>>>
>>>>> On Wed, Aug 20, 2014 at 11:14:12am +0100, Sleepyfox wrote:
>>>>> > Something that might initially sound a bit weird, but suits small
>>>>> apps
>>>>> > well, is using Redis for it's dirt simple Pub/Sub support. It's
>>>>> > trivially easy to use Redis as a message bus (trivially easy to use
>>>>> > Redis, full stop), and if you're not looking for the last word in
>>>>> > sophistication or scale (in which case something like RabbitMQ is
>>>>> > probably a better bet) it does the job.
>>>>> >
>>>>> > The approach is described in the following article (about Node rather
>>>>> > than Ruby, but you get the picture):
>>>>> >
>>>>> > Fox
>>>>> > --
>>>>> > "What does the @sleepyfox say?"
>>>>> >
>>>>> >
>>>>> > On 20 August 2014 09:23, Klaus Hebsgaard <klaus at hebsgaard.dk> wrote:
>>>>> > > Thanks for the pointer, however there were a few points I didn't
>>>>> put into
>>>>> > > the original request:
>>>>> > > - I need something small, as the app is small
>>>>> > > - I don't mind synchronous event busses, as we don't handle
>>>>> anything big
>>>>> > > yet.
>>>>> > > - I would like some simplicity, so adding more processes to run on
>>>>> the
>>>>> > > server, would be too much overhead at the moment
>>>>> > > - We use MRI at the moment, though I can see lots of advantages to
>>>>> JRuby
>>>>> > >
>>>>> > >
>>>>> > >
>>>>> > > Med Venlig hilsen / Best regards
>>>>> > >
>>>>> > > Klaus Hebsgaard
>>>>> > >
>>>>> > > Website: http://www.hebsgaard.dk
>>>>> > > Blog: http://blog.khebbie.dk
>>>>> > > LinkedIIn: http://www.linkedin.com/in/klaushebsgaard
>>>>> > > Github: https://github.com/khebbie
>>>>> > >
>>>>> > >
>>>>> > > On Wed, Aug 20, 2014 at 9:38 AM, Vish Vishvanath <
>>>>> vish.vishvanath at gmail.com>
>>>>> > > wrote:
>>>>> > >>
>>>>> > >> Hey Klaus,
>>>>> > >>
>>>>> > >> On a slightly different note, I've had very positive experiences
>>>>> with Ruby
>>>>> > >> in vert.x,  which enables excellent decoupling with its system of
>>>>> > >> 'verticles': independent code modules communicating via immutable
>>>>> primitives
>>>>> > >> across an event bus.
>>>>> > >>
>>>>> > >> The fact that you can leverage Java and several languages in the
>>>>> same
>>>>> > >> codebase is a bonus.
>>>>> > >>
>>>>> > >> Best
>>>>> > >>
>>>>> > >> vv
>>>>> > >>
>>>>> > >> On 20 Aug 2014, at 07:42, Klaus Hebsgaard <klaus at hebsgaard.dk>
>>>>> wrote:
>>>>> > >>
>>>>> > >> Hello
>>>>> > >>
>>>>> > >> I am currently looking into decoupling my app a bit more.
>>>>> > >> Coming from a C# background I would like to use an Event Bus for
>>>>> this, so
>>>>> > >> that I can apply the observer pattern.
>>>>> > >>
>>>>> > >> I have searched a bit around and have found:
>>>>> > >> https://github.com/kevinrutherford/event_bus
>>>>> > >>
>>>>> > >> Does anyone know this gem, is it worth using (well maintained
>>>>> etc)?
>>>>> > >> Do you know of good alternatives?
>>>>> > >>
>>>>> > >> Med Venlig hilsen / Best regards
>>>>> > >>
>>>>> > >> Klaus Hebsgaard
>>>>> > >>
>>>>> > >> Website: http://www.hebsgaard.dk
>>>>> > >> Blog: http://blog.khebbie.dk
>>>>> > >> LinkedIIn: http://www.linkedin.com/in/klaushebsgaard
>>>>> > >> Github: https://github.com/khebbie
>>>>> > >>
>>>>> > >> _______________________________________________
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>>>>
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