On Wednesday, May 9, 2018 at 2:05:32 PM UTC-7, [email protected] wrote:
>>> For every connection, we should be able to get the events unique to that
>>> connection in completion queue
>> Pretend you had such an API. Can you share how you would make us of it
>> and what higher-level problem it would let you solve?
>>
>> There may be a different way to solve the same problem that doesn't need
>> a per-connection completion queue...
> We could then do things like act as a proxy service. Clients trying to
> connect to an external server would be redirected to this service. This
> service will then make a connection to actual server for each connected
> client and forward the RPC (of course after some kind of processing that
> involves some policy ).
How do you plan to poll all these completion queues? There's no pollset-like
API for completion queues. I can see two ways to poll a bunch of completion
queues, neither of which looks scalable:
1. Have a dedicated poller thread per completion queue.
* This will result in lots of threads that are mostly idle. Stack space
is wasted, there will be scheduling overhead, &c.
2. Have a small number of poller therads and use grpc_completion_queue_next
with a small, but non-zero deadline and cycle to the next completion
queue to check when GRPC_QUEUE_TIMEOUT is returned.
* Completion queues with work that are "behind" completion queues with
no work will get starved.
Instead, I think you want to explore an architecture where you multiplex all
the client connections over a handful of completion queues. In the data
structures you use for to track the outstanding operations (typically what
you pass the address of as the void* tag value), one of the values could be
a client identifier that you could use for whatever client-specific logic
you need in your processing.
Hope this helps.
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