5 ms·

I've often wondered how well an ircd would scale as a twitter clone. Following someone would just joining a channel that only they could write to. I wonder ho

by cagenut 16y ago

I've often wondered how well an ircd would scale as a twitter clone. Following someone would just joining a channel that only they could write to. I wonder how many clients are connected and receiving realtime messages during peak usage on say efnet. edit: sorry I clearly phrased this poorly, I said "an ircd" but in my brain I was thinking of an ircd network like efnet, freenode, etc.

deleted 16y ago
[deleted]
ig1 16y ago
Not that many, even the big IRC networks only run at around 65-85k simultaneous users. The netsplit website has been doing IRC analytics since '98: http://irc.netsplit.de/networks/top100.php http://irc.netsplit.de/networks/top100.php
unwind 16y ago
I might be naive, but to me "connected" to an IRC server implies having an open TCP/IP connection. That means that the server will run out of ports at roughly 65,000 clients. Of course, you could probably solve that by load-balancing, having multiple parallel ircd instances that share the backend, but then you're not having "an ircd" any longer.
- hackermom 16y ago
  No, the server is only using a single port - the one it's listening to. It's also already standard to run multiple, local relays per server instance in the case of IRCds. Many servers run multiple instances that together span 3 or 4 ports; 6667, 6668, 6669 etc.
- dfox 16y ago
  Having multiple instances of ircd is the main point of IRC protocol, that is what the R (as in Relay) stands for.
  - wmf 16y ago
    In a world where a single server can support over 100K connections, I wonder if server-to-server support is needed. You could probably simplify an ircd significantly by making it centralized.
    - jarek 16y ago
      In a world where IRC networks are frequently DDoS attacked by scriptkiddies (and others), a single point of failure is not worth the simplification.
      - wmf 16y ago
        It seems like if you can DDoS one server, you can DDoS several, but I'm no expert. Also, I thought one of the major motivations for IRC DoSes was to cause netsplits that allow nick stealing; a single sever can't have a netsplit.
- koenigdavidmj 16y ago
  No. TCP connections are identified by a four-tuple of (sender's IP, sender's TCP port, receiver's IP, receiver's port). Thus you are only limited by 65536 connections between a particular server and a particular client.
  - dfox 16y ago
    In fact you are limited to 2^32 (=65536^2) connections between two hosts, as you can vary both ports. But that is only theory. In practice you will run out of some other system resource (kernel memory, file descriptors, slots in connection table...) before reaching this limit.
    - koenigdavidmj 16y ago
      Yes, I meant connections to one particular service. In that case both IP fields and the server port are fixed, so the only varying parameter is the client port number.
      - unwind 16y ago
        And that was, I feel kind of redundant in pointing out, exactly what I meant too.
  - ay 16y ago
    For the most scenarios the maximum number of connections between the same client and server will be smaller, because an unbound client socket would reside in the ephemeral port range: http://en.wikipedia.org/wiki/Ephemeral_port http://en.wikipedia.org/wiki/Ephemeral_port
- Macha 16y ago
  Twitter doesn't run on one server either. In fact there was talk a while back that some particularly famous users have an entire server's worth if traffic.
- abstractbill 16y ago
  That means that the server will run out of ports at roughly 65,000 clients. I wrote the justin.tv chat server (which happens to be based on irc). A single one of our chat machines can handle about 120,000 concurrent connections. Available cpu is the limit, not number of ports.
dfox 16y ago
On EFNet: 40416 44108 :Current global users 40416, max 44108 On IRCNEt: 66290 98675 :Current global users 66290, max 98675 Which is probably significantly less than number of twitter users, but IRC is explicitly designed to be scalable.
- zokier 16y ago
  It was also designed in the eighties to be used in university networks. The scale was a lot smaller back then.
- points 16y ago
  The volume of communication is FAR higher than twitter though, and the number of engaged people is likewise higher.
- abstractbill 16y ago
  Those are actually very small numbers. Justin.TV's chat system, for comparison, has scaled to half a million concurrents. And I had to significantly diverge from the IRC spec to achieve that level of scale.
  - rogerclark 16y ago
    I'm interested in exactly how you diverged. What changes did you make to the protocol (especially in terms of server-server communication) to facilitate that kind of scalability?
deleted 16y ago
[deleted]
stevelosh 16y ago
You mean like tircd or twircd? http://github.com/kore/twircd http://github.com/kore/twircd http://code.google.com/p/tircd/ http://code.google.com/p/tircd/

by cagenut 16y ago

deleted 16y ago

[deleted]

ig1 16y ago

Not that many, even the big IRC networks only run at around 65-85k simultaneous users. The netsplit website has been doing IRC analytics since '98: http://irc.netsplit.de/networks/top100.php http://irc.netsplit.de/networks/top100.php

unwind 16y ago

I might be naive, but to me "connected" to an IRC server implies having an open TCP/IP connection. That means that the server will run out of ports at roughly 65,000 clients. Of course, you could probably solve that by load-balancing, having multiple parallel ircd instances that share the backend, but then you're not having "an ircd" any longer.

hackermom 16y ago
No, the server is only using a single port - the one it's listening to. It's also already standard to run multiple, local relays per server instance in the case of IRCds. Many servers run multiple instances that together span 3 or 4 ports; 6667, 6668, 6669 etc.
dfox 16y ago
Having multiple instances of ircd is the main point of IRC protocol, that is what the R (as in Relay) stands for.
- wmf 16y ago
  In a world where a single server can support over 100K connections, I wonder if server-to-server support is needed. You could probably simplify an ircd significantly by making it centralized.
  - jarek 16y ago
    In a world where IRC networks are frequently DDoS attacked by scriptkiddies (and others), a single point of failure is not worth the simplification.
    - wmf 16y ago
      It seems like if you can DDoS one server, you can DDoS several, but I'm no expert. Also, I thought one of the major motivations for IRC DoSes was to cause netsplits that allow nick stealing; a single sever can't have a netsplit.
koenigdavidmj 16y ago
No. TCP connections are identified by a four-tuple of (sender's IP, sender's TCP port, receiver's IP, receiver's port). Thus you are only limited by 65536 connections between a particular server and a particular client.
- dfox 16y ago
  In fact you are limited to 2^32 (=65536^2) connections between two hosts, as you can vary both ports. But that is only theory. In practice you will run out of some other system resource (kernel memory, file descriptors, slots in connection table...) before reaching this limit.
  - koenigdavidmj 16y ago
    Yes, I meant connections to one particular service. In that case both IP fields and the server port are fixed, so the only varying parameter is the client port number.
    - unwind 16y ago
      And that was, I feel kind of redundant in pointing out, exactly what I meant too.
- ay 16y ago
  For the most scenarios the maximum number of connections between the same client and server will be smaller, because an unbound client socket would reside in the ephemeral port range: http://en.wikipedia.org/wiki/Ephemeral_port http://en.wikipedia.org/wiki/Ephemeral_port
Macha 16y ago
Twitter doesn't run on one server either. In fact there was talk a while back that some particularly famous users have an entire server's worth if traffic.
abstractbill 16y ago
That means that the server will run out of ports at roughly 65,000 clients. I wrote the justin.tv chat server (which happens to be based on irc). A single one of our chat machines can handle about 120,000 concurrent connections. Available cpu is the limit, not number of ports.

dfox 16y ago

On EFNet: 40416 44108 :Current global users 40416, max 44108 On IRCNEt: 66290 98675 :Current global users 66290, max 98675 Which is probably significantly less than number of twitter users, but IRC is explicitly designed to be scalable.

zokier 16y ago
It was also designed in the eighties to be used in university networks. The scale was a lot smaller back then.
points 16y ago
The volume of communication is FAR higher than twitter though, and the number of engaged people is likewise higher.
abstractbill 16y ago
Those are actually very small numbers. Justin.TV's chat system, for comparison, has scaled to half a million concurrents. And I had to significantly diverge from the IRC spec to achieve that level of scale.
- rogerclark 16y ago
  I'm interested in exactly how you diverged. What changes did you make to the protocol (especially in terms of server-server communication) to facilitate that kind of scalability?

deleted 16y ago

[deleted]

stevelosh 16y ago

You mean like tircd or twircd? http://github.com/kore/twircd http://github.com/kore/twircd http://code.google.com/p/tircd/ http://code.google.com/p/tircd/