DB work is a IO operation, and IO shouldn't be done inside a go block (go
blocks use limited thread pools).
So what about something like this?
(defn handle-db [chan]
(thread
(while true
(let [[data result] (<! c)]
(run-db-transaction-as-normal data)
(>! result :done)))))
Now spin up a few of these:
(def db-chan (let [c (chan 4)]
(dotimes [x 4]
(handle-db c))
c))
Now it's trivial to use this from a go block:
(defn db-async [data]
(go
(let [c (chan)]
(>! db-chan [data c])
(<! c))))
So this is the pattern: create processors using threads, then send data to
those processors via a shared channel, passing in a response channel.
Anyways, that's the way I'm thinking these days.
Timothy
On Wed, Jul 31, 2013 at 12:24 PM, Alice <[email protected]> wrote:
> I have an async http handler and I don't want it to consume a thread.
>
> On Thursday, August 1, 2013 3:16:52 AM UTC+9, tbc++ wrote:
>
>> Why not use <!! ?
>>
>> Timothy
>>
>>
>> On Wed, Jul 31, 2013 at 11:58 AM, Alice <[email protected]> wrote:
>>
>>> It doesn't produce a compile time error but I think it's not the correct
>>> code because the transaction can be committed while insert-async! is still
>>> executing.
>>>
>>> On Thursday, August 1, 2013 2:46:29 AM UTC+9, Sean Corfield wrote:
>>>
>>>> On Wed, Jul 31, 2013 at 10:29 AM, Alice <[email protected]> wrote:
>>>> > (go
>>>> > (jdbc/db-transaction [t-con db-spec]
>>>> > (<! (insert-async! t-con :fruit {:name "apple"}))))
>>>>
>>>> Does this work:
>>>>
>>>> (jdbc/db-transaction [t-con db-spec]
>>>> (go
>>>> (<! (insert-async! t-con :fruit {:name "apple"}))))
>>>>
>>>> --
>>>> Sean A Corfield -- (904) 302-SEAN
>>>> An Architect's View -- http://corfield.org/
>>>> World Singles, LLC. -- http://worldsingles.com/
>>>>
>>>> "Perfection is the enemy of the good."
>>>> -- Gustave Flaubert, French realist novelist (1821-1880)
>>>>
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>> “One of the main causes of the fall of the Roman Empire was that–lacking
>> zero–they had no way to indicate successful termination of their C
>> programs.”
>> (Robert Firth)
>>
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“One of the main causes of the fall of the Roman Empire was that–lacking
zero–they had no way to indicate successful termination of their C
programs.”
(Robert Firth)
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