[erlang-questions] {error,emfile}

[Jon Schneider]

Could it be due to FD_SETSIZE ? Even if Erlang itself might be able to
handle many more sockets there are still things constrained by this.

Jon

> Dear all,
> I've built a benchmarking tool and I experience an error when connecting
> more than 1024 clients to a SSL server. The call to ssl:connect/3 returns
> a
> {error,emfile} instead of a Socket.
>
> According to inet POSIX Error Codes [1], emfile corresponds to too many
> open files.
> I'm running from a UBUNTU 14.04 LTS box.
>
> However, I've set my /etc/security/limits.conf with:
>
> *   soft    nofile  999999
> *   hard    nofile      999999
>
> and rebooted the machine. I can see it applied:
>
> $ ulimit -a
> core file size          (blocks, -c) 0
> data seg size           (kbytes, -d) unlimited
> scheduling priority             (-e) 0
> file size               (blocks, -f) unlimited
> pending signals                 (-i) 241197
> max locked memory       (kbytes, -l) 64
> max memory size         (kbytes, -m) unlimited
> open files                      (-n) 999999
> pipe size            (512 bytes, -p) 8
> POSIX message queues     (bytes, -q) 819200
> real-time priority              (-r) 0
> stack size              (kbytes, -s) 8192
> cpu time               (seconds, -t) unlimited
> max user processes              (-u) 241197
> virtual memory          (kbytes, -v) unlimited
> file locks                      (-x) unlimited
>
>
> I've also set /etc/sysctl.conf with:
>
> # number of file descriptors
> fs.file-max=2001000
>
> # extend the ports range
> net.ipv4.ip_local_port_range=1024 65535
>
> # increase the max number of receive and send buffer size
> net.core.rmem_max=33554432
> net.core.wmem_max=33554432
>
> # increase TCP auto-tuning buffer limits settings
> net.ipv4.tcp_rmem=4096 16384 33554432
> net.ipv4.tcp_wmem=4096 16384 33554432
> net.ipv4.tcp_mem=786432 1048576 26777216
>
> # increase the number of memory map areas for the server process
> vm.max_map_count=131060
>
> # swap only to avoid an out of memory condition
> vm.swappiness=0
>
> # try to always keep 64MB of RAM free
> vm.min_free_kbytes=65536
>
> # prevent flooding detection when receiving large number of SYN packets
> # use with care as they can detec DoS attacks
> # needed with artificial loads while running the benchmark
> net.ipv4.tcp_max_tw_buckets=360000
> net.core.somaxconn=4096
> net.ipv4.tcp_max_syn_backlog=16000
> net.ipv4.tcp_syncookies=0
> net.ipv4.tcp_tw_recycle=1
>
> # insure keepalive is enabled - use only if needed
> net.ipv4.tcp_keepalive_time=900
> net.ipv4.tcp_keepalive_intvl=180
> net.ipv4.tcp_keepalive_probes=5
>
> And applied them with sudo sysctl -p /etc/sysctl.conf.
>
> Finally, in my Erlang release I've set into vm.args:
>
> +K true
> +P 2000000
> +Q 1000000
> +A 10
>
> When I run my release and attach to the node, I can see:
>
> 1> erlang:system_info(check_io).
> [{name,erts_poll},
>  {primary,epoll},
>  {fallback,poll},
>  {kernel_poll,epoll},
>  {memory_size,113328},
>  {total_poll_set_size,1243},
>  {fallback_poll_set_size,0},
>  {lazy_updates,true},
>  {pending_updates,0},
>  {batch_updates,false},
>  {concurrent_updates,true},
>  {max_fds,999999},
>  {active_fds,1}]
>
> After all this I cannot connect more than 1024 outgoing HTTPS clients.
>
> Any ideas?
>
> Thank you,
> r.
>
>
>
> [1] http://erlang.org/doc/man/inet.html#id132028
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