[erlang-questions] Erlang Web Libraries & Frameworks

Sam Elliott <>
Fri Aug 12 15:12:55 CEST 2011


On Thu, Aug 11, 2011 at 11:16 AM, Joe Armstrong <> wrote:
> On Thu, Aug 11, 2011 at 11:30 AM, Loïc Hoguin <> wrote:
>> On 08/11/2011 11:01 AM, Joe Armstrong wrote:
>>> If all suppliers of web- frameworks could adopt a common adapter
>>> pattern - it would make
>>> life a lot easier. I realize that this would not allow us to use some
>>> of the finer facilities
>>> offered by an individual web-server, but it would be very useful for the simple
>>> cases of serving up files etc.
>>
>> A lot of people choose the server based on those finer facilities.
>> Adaptor projects are already used by everyone else. See below.
>>
>>> One could have a common API then choose the implementation depending upon
>>> the requirements of the application.
>>
>> This is fine and all, but some servers use lists while others use
>> binaries. The handler code is obviously different so some servers would
>> require converting everything (headers, path, ...) to lists or binary
>> before passing the data to your common handler. There's no clean
>> solution there.
>
> Right, that's why an adaptor is useful. I suspect the differences
> by accident rather than design. I would assume the "natural" way to
> transfer large blobs would be as binaries, and to communicate parsed
> attributes would be a Key-Value proplist of strings and so on.
>
> Having a well defined adaptor interface might have beneficial side effect
> of causeing the sofwtare at either side of the interface to migrate
> towards a set
> of common types in the interface.
>
>>
>> Some projects exist, like simple_bridge for example, but AFAIK they only
>> do lists-based servers for now.
>
> I hadn't heard of simple bridge until you mentioned it - it looks
> pretty much to be what I wanted.
>
>
> @sam - can you add simple_bridge to your list (its at
> https://github.com/etnt/SimpleBridge)

I updated the article this morning. It turns out that Jesse had
mentioned SimpleBridge above when talking about nitrogen.

I'll take a longer look at SimpleBridge with my editor open. My
feeling is that it doesn't quite wrap enough of the interfaces, so I
might start a pull request.

> I wonder how many other adaptor patterns there are: if simple_bridge
> is the web adaptor
> where that the adapters for key-val databases?

I was also planning to write a rundown of Erlang JSON encoders - of
which there aren't as many - perhaps an adapter would be a good idea
here too? That said, their apis are easier as you're just calling
modules, not starting processes.

If you want me to do any more rundowns of other places where there are
loads of competing libraries, just email me and I'll see what I can
do. This one was originally written to scratch an itch and seems to
actually be useful.

Sam

> (( aside -- it is a source of never ending frustration that the
> interfaces to ets and dets are different
>   getting people to change ets or dets is very difficult since we
> don't want to break old code
>   but an adapter would do the job ))
>
>> What's a good solution to this?
>
> I don't know - I suspect good interfaces emerge. It's often not
> apparent at the start of a project what
> the best API is. We can't abstract over several interfaces until we
> have several interfaces.
> Once the problem is well understood and we have several implemenations
> we can begin to
> generalize and abstract out what should have been the interface. Then
> we have to refactor our programs.
> (( This is the 99% hard-work part - software gets continually polished ))
>
> /Joe
>
>
>> --
>> Loďc Hoguin
>> Dev:Extend
>>
>



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