Re[2]: [HACKERS] Re[2]: [HACKERS] Connect from background worker thread to database

Понедельник, 25 ноября 2013, 13:31 +09:00 от Michael Paquier <michael(dot)paquier(at)gmail(dot)com>:
>On Mon, Nov 25, 2013 at 1:02 PM, Alexey Vasiliev < leopard_ne(at)inbox(dot)ru > wrote:
>> Thanks, I just try this. This work if I working with database in loop inside
>> bgw_main function. But if I create threads inside bgw_main and try to
>> connect to database - I have errors "stack depth limit exceeded" . The code:
>>
>> https://github.com/le0pard/pg_web/blob/master/src/pg_web.c#L195 - connect to
>> database
>> https://github.com/le0pard/pg_web/blob/master/src/pg_web.c#L100-L131 -
>> "http_event_handler" function execute in threads, because it handle http
>> requests. And this code not work. BTW, I need connect to database depend
>> from request url, so execute BackgroundWorkerInitializeConnection at the
>> beginning not enough.
>There is a design problem with your application when trying to create
>threads with mg_start in order to grab events. Note that I am not
>familiar with mongoose, but with bgworkers you cannot simply create
>new threads that would be able to connect to server concurrently. A
>model that would be more suited with bgworkers would be something
>like:
>- Handle event messages by for example opening a port or monitoring
>the events on a single bgworker launched by bgw_main, with for example
>a message queue model (possible with 9.3). Connection to database
>would be done with a single connection, managed within the loop of
>bgw_main.
>- Create a new bgworker dynamically each time a new event comes in
>(possible only with 9.4~). The top work would be done by a central
>bgworker initialized with server, which would treat events and kick
>new slave workers when necessary.
>
>Regards,
>--
>Michael
>
>
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Thanks. I will look how to do this in the best way by your suggestions.

--
Alexey Vasiliev