[zeromq-dev] disabling receiving messages from queue

[Pavel Gushcha]

Sorry, forgot about attach :-)

2009/8/8 Pavel Gushcha <pavimus at gmail.com>

> Patch is attached. I didn't use "api->receive (&msg, false, 1 << queue_id1
> | 1 << queue_id2)" because in this case api_thread_t is limited to 32 or 64
> queues. I added std::vector<bool> to api_thread_t for storing queues
> statuses, and function set_queue_status(queue_,enabled_) for changing queue
> statuses.
>
> PS: may be adding function "bool get_queue_status(int queue_) {return
> queues_statuses[queue_-1];}" will be too good thing.
>
> 2009/8/4 Martin Sustrik <sustrik at fastmq.com>
>
> Hi Pavel,
>>
>>
>>  Can I disable receiving messages from spcecified queue by
>>> api_thread_t::receive()?
>>> Real use case: my application has one api_thread_t, it receives requests,
>>> process it and sends responses. While processing request, it sends/receives
>>> messages to another applications. I want to implement limit for number of
>>> currently processing messages. Easiest implementation for me looks like
>>> this: when number of currently processing request goes above limit, i block
>>> receiving messages from requests queue. In this case only messages that used
>>> in processing will be received, no new request messages.
>>>
>>> Now i'm thinking about:
>>> 1) more complex realization with two api_thread_t, non-blocking receive()
>>> and sleep() functions.
>>> 2) more complex realization with blocking receive() but with two
>>> application threads with syncronization between them.
>>>
>>> May be threre is more elegant solution for my situation?
>>>
>>
>> No, there isn't :(
>>
>> What you speak about actually boils down to the need for polling on
>> arbitrary subset of queues.
>>
>> Rather than implementing 1. or 2. you may consider submitting a patch to
>> 0MQ that would allow for receiving only from a subset of queues. Say:
>>
>> api->receive (&msg, false, 1 << queue_id1 | 1 << queue_id2);
>>
>> Have a look at the implementation of zmq::api_thread_t::receive function.
>> It's actually a pretty dumb loop that round robins through the list of
>> queues and fetches a message from one of them.
>>
>> Making it ignore subset of queues seems to be a pretty trivial change.
>>
>> Thoughts?
>> Martin
>>
>
>
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