I've been playing with the Tcp module for a while now, trying to use it to build a Memcached client that performs as well as the spymemcached java client does. I got stuff working a while back with the plain Tcp extension but the code was tricky (back pressure handling) and always seemed to hit a bottleneck at around 10K QPS; it will plateau there and never go higher. The spymemcached client, which uses a single I/O thread can get going up to 100K QPS (pipelining multiple requests into a single write to the outbound channel). I recently converted my code to use StreamTcp now, hoping this would be cleaner (it is) and also possibly remove that unexplained bottleneck. Unfortunately it still hits the same bottleneck, even though I am pipelining too (via a groupWithin). The only way I can get above 10K QPS is to create multiple clients, each opening its own StreamTcp connection, but this is not a great idea; I should be able to achieve high throughput on this long lived connection with only a single connection into memcached.
A few things to note: - My Memcached client actor connects via StreamTcp.Connect - On the resulting OutboundTcpConnection, I create two Flows; one for outbound data, one for inbound - The outbound Flow uses a custom ActorPublisher at the head of the Flow and the Flow looks like this: ActorPublisher -> groupWithin -> map (to fold the multiple requests into one mega request) -> produceTo(outboundConnection) - The Custom Publisher uses an internal Queue (a mutable java.util.Queue for perf reasons) that it will add to if there is no demand - The inbound Flow uses a custom ActorSubscriber at the tail of the Flow and the Flow looks like this: Inbound Connection -> transform (for memcached frame decoding) -> produceTo(Custom Subscriber) I know it's going to be tough to completely diagnose this issue without seeing my code, and I'm willing to share it, but I wanted to reach out first and see if this type of situation is a known issue or not. Is there an issue trying to do a very high throughput single StreamTcp connection? FWIW, on the custom publisher, I generally only ever see the demand at 4 when I get a Request message so it seems as if the downstream stuff is exhibiting significant back pressure on me. -- >>>>>>>>>> Read the docs: http://akka.io/docs/ >>>>>>>>>> Check the FAQ: >>>>>>>>>> http://doc.akka.io/docs/akka/current/additional/faq.html >>>>>>>>>> Search the archives: https://groups.google.com/group/akka-user --- You received this message because you are subscribed to the Google Groups "Akka User List" group. To unsubscribe from this group and stop receiving emails from it, send an email to akka-user+unsubscr...@googlegroups.com. To post to this group, send email to akka-user@googlegroups.com. Visit this group at http://groups.google.com/group/akka-user. For more options, visit https://groups.google.com/d/optout.
