haproxyulimit
In the haproxy config file, there is a directive called maxconn.
does this directive refer to concurrent connections? Or once the connection is redirected to a server, it is closed? For example, if the maxconn is set to 4000, and in my whole website there are 10k people, would that directive limit that users number?
Thank you
What makes you think you are limited to 64K clients? You should be able to serve more than that. It's not the port count that is the limiting factor, but the memory and CPU power that limits the amount of connections you can have open at any given time. Check: http://www.kegel.com/c10k.html which is dated, just think of it as a c100k or c1M problem instead. :-)
By the way the haproxy site has an excellent article on the subject of load balancing and haproxy's architecture: http://haproxy.1wt.eu/download/1.2/doc/architecture.txt
Regarding connection limit, this is a theoretical limit that normally you wouldn't reach as you'd run out of resources before that.
"The TCP standard sets up unique connection identifiers as the tuple of local IP address, local TCP port number, remote IP address, and remote TCP port number. In your example, the local numbers are both fixed, which leaves approximately 2^32 remote IP (version 4) addresses, and 2^16 TCP port numbers, or an approximate total potential simultaneous TCP connections of 281,474,976,710,656 (2^48, or 2.81 * 10^14, or 281 trillion)."
The connections you listed in the first paragraph are either ESTABLISHED or in process of being cleaned up after they have been used. Established means what the name implies. A connection is established between one of your users and the HAProxy. Usage as intended.
The other states you mention in the first paragraph all indicate that an previously established connection has finished transferring data. The best way I can explain that is with a diagram.
Briefly: If you have a lot of FIN_WAIT 1 and FIN_WAIT 2's then there is nothing wrong with the server. You are simply waiting for the clients to finish.
Since it is not a problem with the server, adding more users should not be a problem until you hit kernel network limits. You did not post what those are, so I can not comment on how close you are to them.
Best Answer
It sets the maximum number of concurrent connections. Each connection lasts as long as that request (or, with keep-alive, that set of requests).
So, yes, if all 10,000 users are making a request at the exact same time, then a
maxconnsetting of 4000 will limit that.Additionally, most modern browsers open more than one TCP connection when they have a long list of resources to request - this multiplexing allows for resources to load more quickly in general, but increases the effective number of connections that your load balancer sees.