The *riak-client* var

[David James]

I was a little surprised that Welle holds the client in the *riak-client* var. It makes the API clean for a single connection. However, how would one handle multiple connections?

This question is similar to what I was thinking:

http://stackoverflow.com/questions/3267905/best-practice-for-globals-in-clojure-refs-vs-alter-var-root

Are there other API styles that were considered? (Such as passing a database handle to the API returning a new 'updated' handle?) Perhaps the other styles they passed over for some reason or another? I'm just trying to understand.

Thanks,

David

[Michael Klishin]

2013/1/22 David James <david...@gmail.com>

Are there other API styles that were considered? (Such as passing a database handle to the API returning a new 'updated' handle?) Perhaps the other styles they passed over for some reason or another? I'm just trying to understand.

For multiple connections, there is welle.core/with-client:

https://github.com/michaelklishin/welle/blob/master/src/clojure/clojurewerkz/welle/core.clj#L105 as well as

connection functions that simply returns a client instance rather than altering the var.

Apps that use multiple clients is a rare case. Having a more straightforward API for the common case

is way more important. This is also how Monger, Neocons, Elastisch and Langohr work.

If with-client is missing from the docs, it should be added. Feel free to submit a pull request (see 

Monger docs for example, http://clojuremongodb.info).
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MK

http://github.com/michaelklishin
http://twitter.com/michaelklishin

[Oleksandr Petrov]

I would say that Refs actually serve quite a different purpose.

`alter-var-root` is not the core feature of dynamic vars. Although, bindings are. *riak-client* is a dynamic var (which is indicated by its name). 

For example, marco `with-connection`: https://github.com/michaelklishin/welle/blob/master/src/clojure/clojurewerkz/welle/core.clj#L105-L108 would not be as easy to implement and use with refs. Bindings are thread and scope local, so you can be absolutely sure that client instance that you're passing and using within binding is used there exclusively.

Also, it eases testing. As you can see `alter-var-root` is used only once, after that, for ease of use, same instance is passed along. Nothing forbids you from creating an arbitrary number of clients and using them in binding.

Thanks for checking out Welle.

Alex

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alex p

[David James]

Thanks for explaining.

"Nothing forbids you from creating an arbitrary number of clients and using them in binding." Do you have a quick example of how to do this?

[Michael Klishin]

2013/1/22 David James <david...@gmail.com>

"Nothing forbids you from creating an arbitrary number of clients and using them in binding." Do you have a quick example of how to do this?

This is what with-client is for.

https://gist.github.com/449504b29ee63ff2e15a