I am designing a subscription API through gRPC in which:
- Request is stream of subscription filters, updated as client sees fit
- Response is stream of messages matching subscription filters
The goal is to have a single thread responsible for polling the
subscriptions for updated filters, performing queries to create results
sets for the filters, and publishing these results back out to the clients.
Currently, I have something like the following:
rpc Subscribe(stream Request) returns (stream Response);
def Subscribe(self, request_iterator, context):
response_queue = Queue.Queue()
subscription_manager.register_subscription(request_iterator,
response_queue)
while True:
response = response_queue.get(timeout=0.5)
yield response
except Queue.Empty:
return
The first issue is that exposure to the stream of requests is provided
through an iterator interface which blocks on next(). In order to have a
single thread responsible for pulling requests, I need to have access to a
non-blocking way to check if any requests are present the subscription and
advance to the next subscription if not. In order to ensure that a lack of
requests on one subscription doesn't block consumption of requests on
another, I currently have to dedicate a thread per subscription each
blocking on iteration over the request_iterator and applying updates as
they are received.
The second issue is that exposure to the stream of responses is such that
the rpc implementation is expected to be a generator of the responses. My
assumption is that the above code consumes a server worker thread for the
duration of a subscription call.
Overall this translates to 1 thread per subscription for iterating
requests, 1 thread per subscription for yielding responses, and 1 thread
iterating over the subscription params, querying, and populating the
queues. Is there any lower-level access to the streams, i.e. something that
can be selected over for the requests, etc?
Thank you.
--
You received this message because you are subscribed to the Google Groups
"grpc.io" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at https://groups.google.com/group/grpc-io.
To view this discussion on the web visit
https://groups.google.com/d/msgid/grpc-io/cfbb6383-642b-4995-9c54-49b75c502fd2%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
