These are interesting code listings and questions, but they conflate the
syntactic detail that core.async's go is implemented as a macro, with the
semantic intention to support designs around lightweight data flow between
independent code blocks.
It might be of value to check out Go, the language, with its channels and
go-routines, which were part of the inspiration for core.async. In Go,
channels and go-routines are language rather than library features. Go also
lacks macros. In that context, answers to these questions are clear: e.g.
if you want to run an insert asynchronously and then run a select following
the insert in the context of the same transaction, the only way to do it
looks like Timothy's example, where the code implements a data flow- the
particular data to insert and select is sent over a channel, handled by a
function running in a go routine whose semantic purpose is to wait on an
input channel, do the database operation, and stick the result on an output
channel.
>From on the other thread, Go doesn't have exceptions, but error handling
between go routines is usually handled with a separate error channel that
again serves to support data flow, rather than control flow. Similarly,
the reason that a special channel-aware throw wasn't included in core.async
is that the idea isn't to use go blocks in a lexical, control-flow sense-
even though that's what the implementation expands to- it's to support
completely different data-flow oriented designs.
Hope that helps...
On Thu, Aug 1, 2013 at 5:57 AM, Alice <dofflt...@gmail.com> wrote:
> What if I want to run a select query in the middle of a transaction?
>
>
> On Thursday, August 1, 2013 3:33:29 AM UTC+9, tbc++ wrote:
>
>> 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 <doff...@gmail.com> 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 <doff...@gmail.com> 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 <doff...@gmail.com> 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)
>>>>>>
>>>>> --
>>>>> --
>>>>> You received this message because you are subscribed to the Google
>>>>> Groups "Clojure" group.
>>>>> To post to this group, send email to clo...@googlegroups.com
>>>>>
>>>>> Note that posts from new members are moderated - please be patient
>>>>> with your first post.
>>>>> To unsubscribe from this group, send email to
>>>>> clojure+u...@**googlegroups.com
>>>>>
>>>>> For more options, visit this group at
>>>>> http://groups.google.com/**group**/clojure?hl=en<http://groups.google.com/group/clojure?hl=en>
>>>>> ---
>>>>> You received this message because you are subscribed to the Google
>>>>> Groups "Clojure" group.
>>>>> To unsubscribe from this group and stop receiving emails from it, send
>>>>> an email to clojure+u...@**googlegroups.com.
>>>>>
>>>>> For more options, visit
>>>>> https://groups.google.com/**grou**ps/opt_out<https://groups.google.com/groups/opt_out>
>>>>> .
>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>>
>>>> --
>>>> “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)
>>>>
>>> --
>>> --
>>> You received this message because you are subscribed to the Google
>>> Groups "Clojure" group.
>>> To post to this group, send email to clo...@googlegroups.com
>>> Note that posts from new members are moderated - please be patient with
>>> your first post.
>>> To unsubscribe from this group, send email to
>>> clojure+u...@**googlegroups.com
>>> For more options, visit this group at
>>> http://groups.google.com/**group/clojure?hl=en<http://groups.google.com/group/clojure?hl=en>
>>> ---
>>> You received this message because you are subscribed to the Google
>>> Groups "Clojure" group.
>>> To unsubscribe from this group and stop receiving emails from it, send
>>> an email to clojure+u...@**googlegroups.com.
>>> For more options, visit
>>> https://groups.google.com/**groups/opt_out<https://groups.google.com/groups/opt_out>
>>> .
>>>
>>>
>>>
>>
>>
>>
>> --
>> “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)
>>
> --
> --
> You received this message because you are subscribed to the Google
> Groups "Clojure" group.
> To post to this group, send email to clojure@googlegroups.com
> Note that posts from new members are moderated - please be patient with
> your first post.
> To unsubscribe from this group, send email to
> clojure+unsubscr...@googlegroups.com
> For more options, visit this group at
> http://groups.google.com/group/clojure?hl=en
> ---
> You received this message because you are subscribed to the Google Groups
> "Clojure" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to clojure+unsubscr...@googlegroups.com.
> For more options, visit https://groups.google.com/groups/opt_out.
>
>
>
--
--
You received this message because you are subscribed to the Google
Groups "Clojure" group.
To post to this group, send email to clojure@googlegroups.com
Note that posts from new members are moderated - please be patient with your
first post.
To unsubscribe from this group, send email to
clojure+unsubscr...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/clojure?hl=en
---
You received this message because you are subscribed to the Google Groups
"Clojure" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to clojure+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/groups/opt_out.
