Issues with dynamic connections about carmine HOT 5 CLOSED

Hi Eric,

Thanks for getting in touch!

The problem you're running into here isn't to do with make-conn-spec, but with the fact that you're trying to define a function of [& body]. Function arguments are evaluated right away - in this case before the bindings established by with-conn are actually in effect.

I might be able to make a suggestion if I understood better what you're trying to accomplish. I'm not familiar with Hyperion - took a look at the page just now, but couldn't find a simple description of what expectations it has for adapter APIs.

Could you point me toward a simple spec somewhere?

from carmine.

Hey Peter,

I'll give a quick run-down on how Hyperion works. Hyperion has a bunch of DataStores. Each one for a different database. The datastore is created with an database argument, which is then passed to each of its functions.

I would like to treat this database argument like the carmine macro. Example.

If I can get the first two specs of this file to pass I think I'll have smooth sailing from there.

from carmine.

Okay, I looked over the links briefly.

So can I clarify:

1. You're trying to implement hyperion.abstr/Datastore for Carmine.
2. https://github.com/ekosz/hyperion/blob/redis/redis/src/hyperion/redis.clj is working already?
3. You'd like to now make the connection stuff configurable through open-db?

Is that right?

I would like to treat this database argument like the carmine macro. Example.

Are you saying you're trying to get db to behave like the with-conn macro? That won't be possible (the one's a function, the other a macro), but it also doesn't seem like it should be necessary if all you want to do is satisfy #3 above.

What stops you from just giving the desired connection pool & spec to each with-conn call?

So, for example, something like:

(defn- save-record [db record]
  (let [kind (:kind record)
        key (name (:key record))
        my-pool  (some-fn db)
        my-spec (some-fn db)]
    (carmine/with-conn my-pool my-spec
      (r/set (str kind ":" key) record))
    record))

I'm not sure what form db takes exactly, but I'm assuming the options are somehow accesible through it, right?

So maybe something like:

(defn open-db [options]
  (let [defaults {:host "127.0.0.1" :port 6379 :password nil :timeout 0 :db 0}
        pool (r/make-conn-pool :max-active 8)
        connection-spec (merge defaults options)]
    {:pool pool :spec connection-spec})))

Then assuming open-db returns the db that's gonna get passed to save-record...

(defn- save-record [db record]
  (let [kind (:kind record)
        key (name (:key record)]
    (carmine/with-conn (:pool db) (:spec db)
      (r/set (str kind ":" key) record))
    record))

Disclaimer: I may have completely misunderstood how the API is working :)

from carmine.

Alrighty, I was able to come up with a nice compromise where I didn't have to repeat myself too much. Thank you for your help!

You can check out the redis module of Hyperion here.

from carmine.

Cool- that seems perfect.

A few other comments in case they're helpful:

• open-db would also be a good place to allow overriding the connection pool options if you wanted. There's no overlap between pool and connection-spec options, so you could just lump the two together in the single options map.
• I'm not sure how concerned you are about performance, but be aware that r/keys is O(n) so if this is being called often, you may prefer to maintain your own list of keys in a ist or some other kind of index.

Cheers!

from carmine.