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xmppwebsocketmessagingpublish-subscribeserver-push

server push for millions of concurrent connections

I am building a distributed system that consists of potentially millions of clients which all need to keep an open (preferrably HTTP) connection to wait for a command from the server (which is running somewhere else). The load of messages / commmands will not be very high, maybe one message / sec / 1000 clients which means it would be 1000 msg/sec @ 1 million clients. => it's basically about the concurrent connections.

The requirements are simple too. One way messaging (server->client), only 1 client per "channel".

I am pretty open in terms of technology (xmpp / websockets / comet / ...). I am using Google App Engine as server, but their "channels" won't work for me unfortunately (too low quotas and no Java client). XMPP was an option but is quite expensive. So far I was using URL Fetch & pubnub, but they just started charging for connections (big time).

So:

  1. Does anyone know of a service out there that can do that for me in an affordable way? Most I have found restrict or heavily charge for connections.

  2. Any experience with implementing such a server yourself? I have actually done that already and it works pretty well (based on Tomcat & NIO) but I haven't had the time yet to actually set up a large load test environment (partially because this is still a fallback solution, I'd prefer a battle hardened msg server). Any experience to how many users you get per GB? Any hard limits?

My architecture also allows to fragment the msg servers, but I'd like to maximize the concurrent connections because the msg processing CPU overhead is minimal.

Solution

  • I have meanwhile implemented my own message server using netty.io. Netty makes use of Java NIO and scales extremely well. For idle connections I get a memory footprint of 500 bytes per connection. I am doing only very simple message forwarding (no caching, storage or other fancy stuff) but with that am easily getting 1000 - 1500 msg / sec (each half a KB) on the small amazon instance (1ECU / 1.6GB).

    Otherwise if you are looking for a (paid) service then I can recommend spire.io (they do not charge for connections but have a higher price per message) or pubnub (they do charge for connections but are cheaper per message).