Concurrent networking in Scala

I have a working prototype of a concurrent Scala program using Actors. I am now trying to fine tune the number of different Actors, etc..

One stage of the processing requires fetching new data via the internet. Of course, there is nothing I can really do to speed that aspect up. However, I figure if I launch a bunch of requests in parallel, I can bring down the total time. The question, therefore, is:

=>开发者_开发百科 Is there a limit on concurrent networking in Scala or on Unix systems (such as max num sockets)? If so, how can I find out what it is.

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In Linux, there is a limit on the number of open file descriptors each program can have open. This can be seen using the ulimit -n. There is a system-wide limit in /proc/sys/kernel/file-max.

Another limit is the number of connections that the Linux firewall can track. If you are using the iptables connection tracking firewall this value is in /proc/sys/net/netfilter/nf_conntrack_max.

Another limit is of course TCP/IP itself. You can only have 65534 connections to the same remote host and port because each connection needs a unique combination of (localIP, localPort, remoteIP, remotePort).

Regarding speeding things up via concurrent connections: it isn't as easy as just using more connections.

It depends on where the bottlenecks are. If your local connection is being fully used, adding more connections will only slow things down. If you are connecting to the same remote server and its connection is fully used, more will only slow it down.

Where you can get a benefit is when your local connection is not fully used and you are connecting to multiple remote hosts.

If you look at web browsers, you will see they have limits on how many connections will be made to the same remote server. They also have limits on how many connections will be made in total.